Ugt2a1

UniProt ID: P36510
Organism: Rattus norvegicus
Review Status: COMPLETE
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Gene Description

Ugt2a1 encodes the olfactory UDP-glucuronosyltransferase (UGT-olf), a UGT2A-subfamily enzyme enriched in the olfactory epithelium that glucuronidates odorants and other lipophilic substrates, contributing to phase II biotransformation and to perireceptor odorant clearance/signal termination. The enzyme localizes to the plasma membrane of olfactory cilia, proximal to odorant receptors, where its glucuronidation activity modulates the olfactory response in a substrate-dependent manner. Its primary molecular function is glucuronosyltransferase activity in a xenobiotic/odorant metabolic context, with bile-acid glucuronidation as a non-core detoxification role.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0015020 glucuronosyltransferase activity
IBA
GO_REF:0000033 		ACCEPT
Summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the documented core enzymatic role or its direct pathway consequence (IBA, GO_REF:0000033).
Reason: glucuronosyltransferase activity is directly supported by the curated function of Ugt2a1 and is not merely a downstream phenotype or expression response.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
UGT2A1 is a **phase II xenobiotic‑metabolizing enzyme** that catalyzes **glucuronidation**: transfer of glucuronic acid from **UDP‑glucuronic acid (UDPGA)** to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing **more hydrophilic glucuronides** that tend to be eliminated more readily.
GO:0008194 UDP-glycosyltransferase activity
IEA
GO_REF:0000002 		MODIFY
Summary: UDP-glycosyltransferase activity captures part of Ugt2a1 biology, but more specific replacement term(s) better represent the supported function (IEA, GO_REF:0000002).
Reason: UDP-glycosyltransferase activity is too broad or imprecise for Ugt2a1; replace with the more specific supported term(s): GO:0015020 glucuronosyltransferase activity.
Proposed replacements: glucuronosyltransferase activity
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
GO:0015020 glucuronosyltransferase activity
IEA
GO_REF:0000120 		ACCEPT
Summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the documented core enzymatic role or its direct pathway consequence (IEA, GO_REF:0000120).
Reason: glucuronosyltransferase activity is directly supported by the curated function of Ugt2a1 and is not merely a downstream phenotype or expression response.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
GO:0016020 membrane
IEA
GO_REF:0000044 		MODIFY
Summary: membrane is too broad; immunogold EM localizes UGT2A1 to the plasma membrane of olfactory cilia, supporting the more specific ciliary membrane term (IEA, GO_REF:0000044).
Reason: membrane is overly generic. Immunogold electron microscopy localizes UGT2A1 to the plasma membrane of olfactory cilia (a cell-projection/plasma membrane location proximal to odorant receptors), so the annotation should be upgraded to the more specific CC term GO:0060170 ciliary membrane.
Proposed replacements: ciliary membrane
Supporting Evidence:
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
Critically, immunogold EM supports localization of UGT2A1 at the **plasma membrane of olfactory cilia**—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space
GO:0006805 xenobiotic metabolic process
ISO
GO_REF:0000121 		ACCEPT
Summary: xenobiotic metabolic process is retained for Ugt2a1 because it matches the documented core enzymatic role or its direct pathway consequence (ISO, GO_REF:0000121).
Reason: xenobiotic metabolic process is directly supported by the curated function of Ugt2a1 and is not merely a downstream phenotype or expression response.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
A neuro‑olfactory UGT review explicitly frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route
GO:0009608 response to symbiont
ISO
GO_REF:0000121 		REMOVE
Summary: response to symbiont should not be retained for Ugt2a1 based on the combined gene function and cited/source evidence (ISO, GO_REF:0000121).
Reason: The available evidence supports Ugt2a1's curated activity rather than response to symbiont; this annotation is unsupported, assigned to the wrong biological context, or too misleading to keep as non-core.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
GO:0015020 glucuronosyltransferase activity
ISS
GO_REF:0000024 		ACCEPT
Summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the documented core enzymatic role or its direct pathway consequence (ISS, GO_REF:0000024).
Reason: glucuronosyltransferase activity is directly supported by the curated function of Ugt2a1 and is not merely a downstream phenotype or expression response.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
GO:0015020 glucuronosyltransferase activity
ISO
GO_REF:0000121 		ACCEPT
Summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the documented core enzymatic role or its direct pathway consequence (ISO, GO_REF:0000121).
Reason: glucuronosyltransferase activity is directly supported by the curated function of Ugt2a1 and is not merely a downstream phenotype or expression response.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
GO:0016020 membrane
ISS
GO_REF:0000024 		MODIFY
Summary: membrane is too broad; immunogold EM localizes UGT2A1 to the plasma membrane of olfactory cilia, supporting the more specific ciliary membrane term (ISS, GO_REF:0000024).
Reason: membrane is overly generic. Immunogold electron microscopy localizes UGT2A1 to the plasma membrane of olfactory cilia (a cell-projection/plasma membrane location proximal to odorant receptors), so the annotation should be upgraded to the more specific CC term GO:0060170 ciliary membrane.
Proposed replacements: ciliary membrane
Supporting Evidence:
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
Critically, immunogold EM supports localization of UGT2A1 at the **plasma membrane of olfactory cilia**—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space
GO:0007606 sensory perception of chemical stimulus
ISO
GO_REF:0000121 		KEEP AS NON CORE
Summary: sensory perception of chemical stimulus is kept as a non-core process for Ugt2a1. Its enzymatic activity modulates odorant availability in the perireceptor space rather than executing the neurological transduction cascade itself (ISO, GO_REF:0000121).
Reason: GO:0007606 is defined as a neurological process in which an organism receives a chemical stimulus, converts it to a molecular signal, and recognizes/characterizes it. This transduction cascade is executed by olfactory receptor neurons, not by a metabolic enzyme. UGT2A1 glucuronidates odorants and thereby modulates odorant concentration in the perireceptor space (ex vivo electroolfactogram shows topical beta-glucuronidase selectively increases the eugenol response), so it is a modulator of odorant availability rather than a component of the sensory transduction cascade. The annotation is retained as a non-core contextual involvement rather than ACCEPTed as a core function. There is no GO odorant metabolic process term to MODIFY to (the previously suggested GO:0042545 is cell wall modification, a plant term, and GO:0052697 xenobiotic glucuronidation is obsolete); the core metabolic role is captured by the xenobiotic metabolic process and glucuronosyltransferase activity annotations.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
counteracting UGT activity with topical **β‑glucuronidase** increased the EOG response amplitude to **eugenol** but not to **amyl acetate**, consistent with the interpretation that glucuronidation reduces effective eugenol concentration at receptors
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
In the olfactory system, such glucuronidation is part of the **perireceptor process**, i.e., local metabolism in the mucus/epithelium that shapes the concentration-time profile of odorants reaching olfactory receptors and can thereby contribute to **signal termination**
GO:0008206 bile acid metabolic process
ISO
GO_REF:0000121 		KEEP AS NON CORE
Summary: bile acid metabolic process is retained as contextual support for Ugt2a1, but it is not the core function (ISO, GO_REF:0000121).
Reason: bile acid metabolic process records a physiological/substrate context rather than the defining molecular activity of Ugt2a1. This is an ISO annotation transferred from human UGT2A1 (P0DTE4); the supporting Falcon evidence (bile-acid glucuronidation activity) is from human studies, consistent with the ISO basis, and supports retention as a non-core detoxification process distinct from the primary olfactory role.
Supporting Evidence:
UniProtKB:P36510
FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
UGT2A1 is described as **highly active in bile-acid glucuronidation**, and it notes characterization of UGT2A1 variants and disease connections (human context)
GO:0009636 response to toxic substance
TAS
PMID:1900353
Odorant signal termination by olfactory UDP glucuronosyl tra... 		MARK AS OVER ANNOTATED
Summary: response to toxic substance is an over-annotation for Ugt2a1; PMID:1900353 supports odorant glucuronidation and olfactory signal termination rather than a toxicological response process.
Reason: The cited paper establishes glucuronosyltransferase activity toward odorants. That supports the MF annotation and olfactory chemical-stimulus context, but not a broad response to toxic substance biological process. Falcon deep research frames nasal UGTs (including UGT2A1) as a protective metabolic barrier; this is a constitutive detoxification/clearance role rather than an inducible response-to-toxin process, reinforcing that GO:0009636 is an over-annotation.
Supporting Evidence:
PMID:1900353
We report here the molecular cloning and expression of an olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows preference for odorants over standard UGT substrates.
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route
GO:0015020 glucuronosyltransferase activity
TAS
PMID:1900353
Odorant signal termination by olfactory UDP glucuronosyl tra... 		ACCEPT
Summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the documented core enzymatic role or its direct pathway consequence (TAS, PMID:1900353).
Reason: glucuronosyltransferase activity is directly supported by the curated function of Ugt2a1 and is not merely a downstream phenotype or expression response.
Supporting Evidence:
PMID:1900353
We report here the molecular cloning and expression of an olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows preference for odorants over standard UGT substrates.

Core Functions

Ugt2a1 glucuronidates odorants and lipophilic substrates as an olfactory UDP-glucuronosyltransferase, contributing to perireceptor odorant clearance and signal termination.

Molecular Function:
glucuronosyltransferase activity
Directly Involved In:
xenobiotic metabolic process
Supporting Evidence:
  • UniProtKB:P36510
    FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory tissue specificity, and therefore may be involved in olfaction.
  • file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
    UGT2A1 is a **phase II xenobiotic‑metabolizing enzyme** that catalyzes **glucuronidation**: transfer of glucuronic acid from **UDP‑glucuronic acid (UDPGA)** to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing **more hydrophilic glucuronides** that tend to be eliminated more readily.

References

GO_REF:0000002
GO reference used by source annotation pipeline
  • Source annotation pipeline provenance for Ugt2a1 annotations including UDP-glycosyltransferase activity.
    "GO_REF entry used only to trace source annotation method; biological support was assessed from UniProt and cached literature where available."
GO_REF:0000024
GO reference used by source annotation pipeline
  • Source annotation pipeline provenance for Ugt2a1 annotations including glucuronosyltransferase activity; membrane.
    "GO_REF entry used only to trace source annotation method; biological support was assessed from UniProt and cached literature where available."
GO_REF:0000033
GO reference used by source annotation pipeline
  • Source annotation pipeline provenance for Ugt2a1 annotations including glucuronosyltransferase activity.
    "GO_REF entry used only to trace source annotation method; biological support was assessed from UniProt and cached literature where available."
GO_REF:0000044
GO reference used by source annotation pipeline
  • Source annotation pipeline provenance for Ugt2a1 annotations including membrane.
    "GO_REF entry used only to trace source annotation method; biological support was assessed from UniProt and cached literature where available."
GO_REF:0000120
GO reference used by source annotation pipeline
  • Source annotation pipeline provenance for Ugt2a1 annotations including glucuronosyltransferase activity.
    "GO_REF entry used only to trace source annotation method; biological support was assessed from UniProt and cached literature where available."
GO_REF:0000121
GO reference used by source annotation pipeline
  • Source annotation pipeline provenance for Ugt2a1 annotations including bile acid metabolic process; glucuronosyltransferase activity; response to symbiont; sensory perception of chemical stimulus; xenobiotic metabolic process.
    "GO_REF entry used only to trace source annotation method; biological support was assessed from UniProt and cached literature where available."
PMID:1900353
Odorant signal termination by olfactory UDP glucuronosyl transferase.
  • For Ugt2a1, this publication was assessed for annotations including glucuronosyltransferase activity; response to toxic substance.
    "We report here the molecular cloning and expression of an olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows preference for odorants over standard UGT substrates."
file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
Falcon (Edison Scientific) deep research report: rat Ugt2a1 (UDP-glucuronosyltransferase 2A1, UGT-olf)
  • Ugt2a1/UGT2A1 is the olfactory UDP-glucuronosyltransferase (UGT-olf), a UGT2A subfamily member enriched in neuro-olfactory tissues, confirming gene identity (UniProt P36510).
    "historically termed **UGT-olf/UGTolf**, a member of the UGT2A subfamily enriched in neuro‑olfactory tissues"
  • UGT2A1 catalyzes glucuronidation, transferring glucuronic acid from UDP-glucuronic acid to nucleophilic acceptors to form more hydrophilic glucuronides, supporting the glucuronosyltransferase molecular function.
    "UGT2A1 is a **phase II xenobiotic‑metabolizing enzyme** that catalyzes **glucuronidation**: transfer of glucuronic acid from **UDP‑glucuronic acid (UDPGA)** to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing **more hydrophilic glucuronides** that tend to be eliminated more readily."
  • Glucuronidation by UGT2A1 is part of the olfactory perireceptor process and can contribute to odorant signal termination, supporting the sensory-perception annotations.
    "In the olfactory system, such glucuronidation is part of the **perireceptor process**, i.e., local metabolism in the mucus/epithelium that shapes the concentration-time profile of odorants reaching olfactory receptors and can thereby contribute to **signal termination**"
  • Glucuronidated odorant metabolites fail to stimulate canonical cAMP signaling in olfactory cilia preparations, mechanistically linking UGT2A1 activity to reduced receptor activation.
    "olfactory cilia preparations show that **glucuronidated odorant metabolites fail to stimulate canonical cAMP signaling**, consistent with a mechanism by which glucuronidation reduces receptor activation and promotes signal termination"
  • Immunogold EM localizes UGT2A1 to the plasma membrane of olfactory cilia (in addition to sustentacular-cell ER), supporting membrane localization proximal to odorant receptors.
    "Critically, immunogold EM supports localization of UGT2A1 at the **plasma membrane of olfactory cilia**—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space"
  • UGT2A1 immunolocalizes broadly in the apical olfactory epithelium including sustentacular cells and Bowman's glands/ducts.
    "localize UGT2A1 broadly within the olfactory epithelium and especially in the apical region, including **sustentacular cells** and **Bowman’s glands/ducts**"
  • Ex vivo electroolfactogram experiments show topical β-glucuronidase selectively increases the eugenol but not amyl-acetate response, giving causal in-situ evidence that glucuronidation modulates the olfactory response.
    "counteracting UGT activity with topical **β‑glucuronidase** increased the EOG response amplitude to **eugenol** but not to **amyl acetate**, consistent with the interpretation that glucuronidation reduces effective eugenol concentration at receptors"
  • UGT2A1 substrate scope extends beyond odorants to coumarins, drugs/xenobiotics and steroids (estradiol/testosterone), supporting broader xenobiotic and steroid handling.
    "monoterpenoid alcohols** (e.g., geraniol, linalool, borneol, menthol), **coumarins** (e.g., umbelliferone derivatives), **drugs/xenobiotics** (e.g., ibuprofen, valproic acid), and **steroids** (e.g., estradiol/testosterone), supporting a role that extends beyond “odorant-only” metabolism and into broader nasal detoxification and local steroid handling"
  • Nasal UGTs including UGT2A1 form a protective metabolic barrier reducing local toxicity and xenobiotic delivery to the brain, supporting the xenobiotic metabolic process role.
    "frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route"
  • Human UGT2A1 is reported highly active in bile-acid glucuronidation, corroborating the bile acid metabolic process annotation as a non-core detoxification role.
    "UGT2A1 is described as **highly active in bile-acid glucuronidation**, and it notes characterization of UGT2A1 variants and disease connections (human context)"

Deep Research

Falcon

(Ugt2a1-deep-research-falcon.md)
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 22 citations 2 artifacts 2026-06-01T03:16:46.984176
Edison artifact artifact-00 (text/markdown)
## Context ID: pqac-00000008 The requested data and micrographs are provided in the following figures: - **EOG Amplitude Changes**: Figure 3 (page 9) shows the (image/png)

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research report: Rat Ugt2a1 (UniProt P36510) — functional annotation of UDP-glucuronosyltransferase 2A1 (UGT2A1/UGT-olf)

Scope and identity verification

The target protein is rat (Rattus norvegicus) UDP-glucuronosyltransferase 2A1 (UGT2A1), historically termed UGT-olf/UGTolf, a member of the UGT2A subfamily enriched in neuro‑olfactory tissues. Its identity as an olfactory UGT is supported by (i) quantitative mRNA enrichment in rat olfactory epithelium relative to olfactory bulb and (ii) proteomic detection in olfactory sensory cilia, and by direct experimental studies on rat olfactory epithelium that immunolocalize UGT2A1 and test its functional impact on odor responses (heydel2010udpglucuronosyltransferases(ugts)in pages 2-3, heydel2010udpglucuronosyltransferases(ugts)in pages 3-5, neiers2021theodorantmetabolizing pages 6-8).

1) Key concepts and definitions (current understanding)

1.1 UDP-glucuronosyltransferases and the glucuronidation reaction

UGT2A1 is a phase II xenobiotic‑metabolizing enzyme that catalyzes glucuronidation: transfer of glucuronic acid from UDP‑glucuronic acid (UDPGA) to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing more hydrophilic glucuronides that tend to be eliminated more readily. In the olfactory system, such glucuronidation is part of the perireceptor process, i.e., local metabolism in the mucus/epithelium that shapes the concentration-time profile of odorants reaching olfactory receptors and can thereby contribute to signal termination (neiers2021theodorantmetabolizing pages 2-4, heydel2010udpglucuronosyltransferases(ugts)in pages 18-19).

1.2 “Perireceptor” odorant metabolism and functional logic

A central mechanistic idea in the olfactory field is that enzymes expressed in the olfactory epithelium (including UGTs) can rapidly biotransform odorants, which can (a) clear odorants and shorten receptor activation or (b) generate metabolites that may become new stimuli. Importantly, olfactory cilia preparations show that glucuronidated odorant metabolites fail to stimulate canonical cAMP signaling, consistent with a mechanism by which glucuronidation reduces receptor activation and promotes signal termination (neiers2021theodorantmetabolizing pages 2-4, heydel2010udpglucuronosyltransferases(ugts)in pages 18-19).

2) Gene product localization and expression (rat-specific)

2.1 Tissue distribution in rat neuro‑olfactory tissues

Quantitative RT‑PCR evidence summarized in a neuro‑olfactory UGT review reports absolute Ugt2a1 mRNA abundance of approximately 9.8 attomoles/µg total RNA in rat olfactory epithelium and 1.6 attomoles/µg in rat olfactory bulb, consistent with strong enrichment in the peripheral olfactory mucosa (heydel2010udpglucuronosyltransferases(ugts)in pages 2-3). Proteomics has detected UGT2A1 in rat olfactory sensory cilia, supporting presence in the odor-detection compartment (heydel2010udpglucuronosyltransferases(ugts)in pages 3-5).

2.2 Cell type and subcellular localization within olfactory epithelium

Direct rat tissue experiments (immunohistochemistry + immunogold electron microscopy) localize UGT2A1 broadly within the olfactory epithelium and especially in the apical region, including sustentacular cells and Bowman’s glands/ducts (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6). Critically, immunogold EM supports localization of UGT2A1 at the plasma membrane of olfactory cilia—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space (neiers2021theodorantmetabolizing media 64d5c307, neiers2021theodorantmetabolizing media e8c32847, neiers2021theodorantmetabolizing media cd8ac3e6).

3) Primary biochemical function: reaction catalyzed and substrate specificity

3.1 Reaction catalyzed

UGT2A1 catalyzes UDPGA-dependent glucuronidation of diverse substrates, including odorants and other xenobiotics/endobiotics encountered by the nasal epithelium (neiers2021theodorantmetabolizing pages 2-4, neiers2021theodorantmetabolizing pages 1-2).

3.2 Substrate scope (odorants and beyond)

An authoritative review of neuro‑olfactory UGTs compiles experimental evidence (from olfactory tissue microsomes and recombinant systems including rat UGT2A1 cDNA expression) indicating UGT2A1 can glucuronidate multiple substrate classes relevant to olfaction and detoxification. Odorant/phenolic substrates glucuronidated in olfactory contexts include eugenol, vanillin, carvacrol, and 1‑naphthol, among others (heydel2010udpglucuronosyltransferases(ugts)in pages 13-14, heydel2010udpglucuronosyltransferases(ugts)in pages 12-13). The same review summarizes additional substrate classes including monoterpenoid alcohols (e.g., geraniol, linalool, borneol, menthol), coumarins (e.g., umbelliferone derivatives), drugs/xenobiotics (e.g., ibuprofen, valproic acid), and steroids (e.g., estradiol/testosterone), supporting a role that extends beyond “odorant-only” metabolism and into broader nasal detoxification and local steroid handling (heydel2010udpglucuronosyltransferases(ugts)in pages 13-14, heydel2010udpglucuronosyltransferases(ugts)in pages 12-13).

3.3 Rat functional evidence for substrate selectivity in situ (odor responses)

A rat ex vivo electroolfactogram (EOG) study used odorants selected for contrasting glucuronidation susceptibility: amyl acetate (not considered a UGT substrate in this context) versus eugenol (described as highly glucuronoconjugated). In this preparation, counteracting UGT activity with topical β‑glucuronidase increased the EOG response amplitude to eugenol but not to amyl acetate, consistent with the interpretation that glucuronidation reduces effective eugenol concentration at receptors (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6). Quantitatively, vehicle application reduced response amplitudes (reported as −20.3 ± 0.17% for amyl acetate and −15.4 ± 0.12% for eugenol), whereas β‑glucuronidase increased eugenol amplitude by +13 ± 0.14% (p = 0.037) while producing no significant change for amyl acetate (neiers2021theodorantmetabolizing pages 6-8). The corresponding figure evidence is shown in the retrieved EOG plot (neiers2021theodorantmetabolizing media 64d5c307).

3.4 Enzyme kinetics: available quantitative benchmarks (primarily human recombinant UGT2A1)

Direct rat UGT2A1 Km/Vmax values were not available in the retrieved full texts. However, detailed kinetic constants exist for human UGT2A1 expressed heterologously. For example, a biochemical characterization of human olfactory UGT2A1 reported apparent kinetic parameters for representative substrates, including odorant-like alcohols and testosterone (e.g., testosterone apparent Km ~56 µM and Vmax ~0.25 nmol/mg/min in the cited system), supporting broad, quantitatively measurable catalytic activity toward odorant-like chemicals and steroids (jedlitschky1999cloningandcharacterization pages 5-6). In another comparative kinetic study of human UGT2A isoforms, UGT2A1 showed much higher affinity (lower Km) than UGT2A2 for several phenolic/coumarin-like probes, illustrating that even within the UGT2A subfamily, substrate affinity can differ substantially by isoform (sneitz2009humanudpglucuronosyltransferaseugt2a2 pages 9-10).

4) Biological processes and pathways

4.1 Peripheral olfactory processing (signal termination and odorant clearance)

UGT2A1’s localization at the apical olfactory epithelium and olfactory cilia, together with substrate-selective EOG modulation by β‑glucuronidase, supports a functional role in odorant clearance and modulation/termination of olfactory signaling in the peripheral olfactory mucosa (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 2-4, neiers2021theodorantmetabolizing media 64d5c307). This is consistent with a broader conceptual framework in which xenobiotic-metabolizing enzymes in the olfactory mucosa shape odorant availability near olfactory receptors (heydel2010udpglucuronosyltransferases(ugts)in pages 18-19, heydel2010udpglucuronosyltransferases(ugts)in pages 17-18).

4.2 Barrier and detoxification function in nasal-to-brain exposure pathways

A neuro‑olfactory UGT review explicitly frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route (heydel2010udpglucuronosyltransferases(ugts)in pages 16-17). This “metabolic barrier” perspective also implies relevance for intranasal drug delivery and toxicology.

5) Recent developments (prioritizing 2023–2024) and clinical relevance

A 2023 systematic review/meta-analysis of omicron-associated olfactory dysfunction highlights a genome-wide association signal at the UGT2A1/UGT2A2 locus, described as encoding an odorant‑metabolizing UDP glycosyltransferase expressed in sustentacular cells. The analysis reports ancestry-stratified prevalence estimates (e.g., 11.6% in populations of European ancestry vs 2.9–5.4% in other major groups) and a global adult prevalence estimate of ~5.2%, projecting ~222.3 million affected adults; the authors argue these prevalence patterns mirror population differences in a UGT2A1 risk-allele frequency and are consistent with UGT2A1 involvement in susceptibility to COVID-related smell loss (bartheld2023prevalenceofolfactory pages 11-15, bartheld2023prevalenceofolfactory pages 1-6). While not rat data, these 2023 findings underscore ongoing biomedical interest in UGT2A-mediated perireceptor metabolism in olfactory function.

5.2 2024: broader detoxification relevance (human bile-acid glucuronidation review)

A 2024 review focused on bile-acid glucuronidation and therapeutic targets cites human studies in which UGT2A1 is described as highly active in bile-acid glucuronidation, and it notes characterization of UGT2A1 variants and disease connections (human context) (gallucci2024pparmediatedbileacid pages 10-11). This supports the interpretation that UGT2A1 can participate in broader detoxification chemistry beyond odorants (though this evidence is not olfaction- or rat-specific).

6) Current applications and real-world implementations

6.1 Intranasal drug delivery and “metabolic barrier” considerations

The nasal route is widely explored for CNS delivery because it can bypass the blood–brain barrier (BBB). In this context, a neuro‑olfactory metabolism review notes that >98% of new CNS-targeted drug candidates do not cross the BBB, motivating intranasal delivery strategies, but it emphasizes that xenobiotic-metabolizing enzymes in nasal epithelium—including UGTs present in olfactory epithelium—can act as a biochemical barrier against nasally administered drugs, potentially lowering bioavailability or altering toxicity profiles (heydel2010udpglucuronosyltransferases(ugts)in pages 17-18, heydel2010udpglucuronosyltransferases(ugts)in pages 16-17). This is a direct, real-world implication of UGT2A1-mediated glucuronidation in the nasal mucosa.

6.2 Toxicology and inhaled chemical/fragrance exposure

UGT2A1’s broad substrate scope (including phenolic odorants like eugenol/vanillin and other volatile compounds) and its strategic localization in the olfactory mucosa support a role in the detoxification of inhaled chemicals and odorants. The same review explicitly frames olfactory epithelial XMEs (including UGTs) as protective against toxicants arriving via systemic circulation and inhalation exposures (heydel2010udpglucuronosyltransferases(ugts)in pages 16-17, heydel2010udpglucuronosyltransferases(ugts)in pages 13-14). Although the retrieved excerpts did not include quantitative regulatory/toxicology performance metrics, UGT2A1 genetic variation has been discussed in the context of tobacco-related cancer susceptibility in the cited literature lists (neiers2021theodorantmetabolizing pages 13-13).

7) Expert interpretation and critical assessment (authoritative analysis)

  1. Localization supports fast, local control of odorant availability. The presence of UGT2A1 at the plasma membrane of olfactory cilia suggests an optimized architecture for rapid odorant metabolism near receptors, rather than exclusively in intracellular ER typical of many UGTs (neiers2021theodorantmetabolizing media 64d5c307, neiers2021theodorantmetabolizing media cd8ac3e6).

  2. Functional evidence in rat is strong for “odorant modulation,” but not a full flux map. The ex vivo EOG experiment provides causal evidence that enzymatic counteraction of glucuronidation changes electrophysiological odor responses in a substrate-dependent manner (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing media 64d5c307). However, the available evidence does not provide a complete in vivo quantification of odorant → glucuronide conversion rates in mucus or full substrate panels for rat UGT2A1 under physiological conditions.

  3. Rat-specific kinetic parameters remain a gap in accessible full text. While human recombinant UGT2A1 kinetics demonstrate broad catalytic capability and facilitate isoform comparisons (jedlitschky1999cloningandcharacterization pages 5-6, sneitz2009humanudpglucuronosyltransferaseugt2a2 pages 9-10), equivalent rat UGT2A1 Km/Vmax values were not retrieved here; functional annotation for rat thus currently rests more on localization, expression, and physiological modulation than on enzyme-kinetic constants.

Summary of key evidence (table)

The table below consolidates the major findings, quantitative data, and study contexts.

Evidence type Finding Quantitative detail Species/tissue Source (with DOI/URL and year)
Gene/protein identity and expression Rat Ugt2a1/UGT2A1 corresponds to the olfactory UDP-glucuronosyltransferase historically termed UGT-olf/UGTolf; highly expressed in olfactory tissues and detected in olfactory sensory cilia (heydel2010udpglucuronosyltransferases(ugts)in pages 2-3, heydel2010udpglucuronosyltransferases(ugts)in pages 3-5) Absolute expression reported as ~9.8 attomoles/µg total RNA in rat olfactory epithelium and ~1.6 attomoles/µg total RNA in rat olfactory bulb; one other isoform reported as >1,000-fold lower than UGT2A1 (heydel2010udpglucuronosyltransferases(ugts)in pages 2-3, heydel2010udpglucuronosyltransferases(ugts)in pages 3-5) Rattus norvegicus; olfactory epithelium, olfactory bulb, olfactory sensory cilia Heydel et al., Drug Metab Rev (2010), DOI: 10.3109/03602530903208363, https://doi.org/10.3109/03602530903208363 (heydel2010udpglucuronosyltransferases(ugts)in pages 2-3, heydel2010udpglucuronosyltransferases(ugts)in pages 3-5)
Enzymatic reaction UGT2A1 is a phase II UDP-glucuronosyltransferase that conjugates UDP-glucuronic acid to odorants/xenobiotics, generating more hydrophilic glucuronides for elimination; this reaction is implicated in olfactory perireceptor metabolism and signal termination (neiers2021theodorantmetabolizing pages 2-4, neiers2021theodorantmetabolizing pages 1-2) Reaction class stated; rapid metabolite formation in olfactory tissue reported on the order of hundreds of milliseconds in the 2021 study background, but no rat-specific Km/Vmax values were provided in the retrieved evidence (neiers2021theodorantmetabolizing pages 1-2) Rat olfactory epithelium / vertebrate olfactory tissues Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029; Heydel et al., Drug Metab Rev (2010), DOI: 10.3109/03602530903208363, https://doi.org/10.3109/03602530903208363 (neiers2021theodorantmetabolizing pages 2-4, neiers2021theodorantmetabolizing pages 1-2)
Tissue/cellular localization UGT2A1 immunolocalizes throughout the olfactory epithelium, especially the apical region; present in sustentacular cells, Bowman glands, and Bowman gland ducts (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6) Qualitative localization by immunohistochemistry; no abundance values at the cell-type level reported in retrieved evidence (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6) Rat olfactory epithelium Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6)
Subcellular localization UGT2A1 is localized not only in sustentacular-cell endoplasmic reticulum but also at the plasma membrane of olfactory cilia of olfactory sensory neurons, placing the enzyme close to odorant receptors (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing media 64d5c307, neiers2021theodorantmetabolizing media e8c32847, neiers2021theodorantmetabolizing media cd8ac3e6) Localization supported by immunogold EM micrographs (Fig. 2E/F in cited paper); no numerical membrane-density values reported in retrieved evidence (neiers2021theodorantmetabolizing media 64d5c307, neiers2021theodorantmetabolizing media e8c32847, neiers2021theodorantmetabolizing media cd8ac3e6) Rat olfactory cilia / olfactory sensory neurons and sustentacular cells Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing media 64d5c307, neiers2021theodorantmetabolizing media e8c32847, neiers2021theodorantmetabolizing media cd8ac3e6)
Substrate specificity: positive exemplar Eugenol is described as a strong/highly glucuronidated odorant substrate of olfactory UGTs/UGT2A1, used as the positive functional probe in rat olfactory epithelium (neiers2021theodorantmetabolizing pages 1-2, neiers2021theodorantmetabolizing pages 4-6) EOG experiments used 10^-2 M eugenol; β-glucuronidase treatment increased response amplitude by +13 ± 0.14%, with p = 0.037 versus vehicle condition summarized in the evidence (neiers2021theodorantmetabolizing pages 6-8) Rat olfactory epithelium Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 1-2, neiers2021theodorantmetabolizing pages 4-6)
Substrate specificity: negative comparator Amyl acetate was used as a comparator because it is not considered a UGT substrate in this rat olfactory assay framework (neiers2021theodorantmetabolizing pages 4-6) EOG experiments used 10^-3 M amyl acetate; β-glucuronidase produced no significant change in the response to amyl acetate, supporting substrate selectivity of the observed effect (neiers2021theodorantmetabolizing pages 6-8) Rat olfactory epithelium Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6)
Functional modulation assay Counteracting glucuronidation in situ with β-glucuronidase altered odor responses in a substrate-dependent manner, supporting UGT2A1-mediated odorant clearance in the perireceptor space (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6) Vehicle alone reduced EOG amplitudes by -20.3 ± 0.17% for amyl acetate and -15.4 ± 0.12% for eugenol; β-glucuronidase caused no significant change for amyl acetate but increased eugenol responses (+13 ± 0.14%, p = 0.037) (neiers2021theodorantmetabolizing pages 6-8) Rat olfactory mucosa / olfactory epithelium Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6)
Experimental conditions Functional evidence came from ex vivo EOG recordings after topical enzyme delivery onto endoturbinates, directly testing whether deconjugation of glucuronides modifies odor responses (neiers2021theodorantmetabolizing pages 4-6) Twenty rats were used; β-glucuronidase from Helix pomatia at 10 mg/mL; topical droplets ~1 µL via ~5 µm pipettes; odor puff 200 ms at 200 mL/min within 1000 mL/min airflow (neiers2021theodorantmetabolizing pages 4-6) Rat olfactory epithelium / endoturbinates IIb and III Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 4-6)
Physiological role UGT2A1 is considered a major odorant-metabolizing enzyme in the olfactory perireceptor process, contributing to odorant elimination/clearance, limiting receptor activation, and promoting signal termination; glucuronidated odorants reportedly fail to stimulate cAMP production in olfactory cilia preparations (neiers2021theodorantmetabolizing pages 2-4, heydel2010udpglucuronosyltransferases(ugts)in pages 18-19, neiers2021theodorantmetabolizing pages 1-2) Functional relationship is supported qualitatively and by substrate-dependent EOG modulation; no direct in vivo rat kinetic flux measurements were reported in retrieved evidence (neiers2021theodorantmetabolizing pages 6-8, heydel2010udpglucuronosyltransferases(ugts)in pages 18-19, neiers2021theodorantmetabolizing pages 1-2) Rat and broader vertebrate olfactory tissues Neiers et al., PLOS ONE (2021), DOI: 10.1371/journal.pone.0249029, https://doi.org/10.1371/journal.pone.0249029; Heydel et al., Drug Metab Rev (2010), DOI: 10.3109/03602530903208363, https://doi.org/10.3109/03602530903208363 (neiers2021theodorantmetabolizing pages 2-4, heydel2010udpglucuronosyltransferases(ugts)in pages 18-19, neiers2021theodorantmetabolizing pages 1-2)
Recent relevance (2023–2024) Although not rat-specific functional work, recent human-focused literature implicates the UGT2A1/UGT2A2 locus in susceptibility to COVID-19-related olfactory dysfunction, consistent with an important role for this odorant-metabolizing pathway in the olfactory epithelium (bartheld2023prevalenceofolfactory pages 11-15, bartheld2023prevalenceofolfactory pages 1-6) Meta-analysis estimated omicron-related olfactory dysfunction prevalence of 11.6% in European-ancestry populations vs 2.9–5.4% in other major groups, with global adult prevalence ~5.2% and ~222.3 million affected adults; prevalence pattern mirrored UGT2A1 risk-allele frequency differences (bartheld2023prevalenceofolfactory pages 11-15, bartheld2023prevalenceofolfactory pages 1-6) Human olfactory epithelium / clinical genetics context von Bartheld & Wang, medRxiv (2023), DOI: 10.1101/2022.12.16.22283582, https://doi.org/10.1101/2022.12.16.22283582 (bartheld2023prevalenceofolfactory pages 11-15, bartheld2023prevalenceofolfactory pages 1-6)

Table: This table summarizes the key functional-annotation evidence for rat Ugt2a1/UGT2A1, including reaction type, substrate examples, localization, physiological role in olfaction, and the main quantitative findings available from the cited sources.

Key cited sources (with publication date and URL)

  • Neiers et al. 2021-03. PLOS ONE. “The odorant metabolizing enzyme UGT2A1: Immunolocalization and impact of the modulation of its activity on the olfactory response.” https://doi.org/10.1371/journal.pone.0249029 (neiers2021theodorantmetabolizing pages 6-8, neiers2021theodorantmetabolizing pages 4-6, neiers2021theodorantmetabolizing media 64d5c307)
  • Heydel et al. 2010-01. Drug Metabolism Reviews. “UDP-glucuronosyltransferases (UGTs) in neuro-olfactory tissues: expression, regulation, and function.” https://doi.org/10.3109/03602530903208363 (heydel2010udpglucuronosyltransferases(ugts)in pages 2-3, heydel2010udpglucuronosyltransferases(ugts)in pages 16-17, heydel2010udpglucuronosyltransferases(ugts)in pages 17-18)
  • von Bartheld & Wang 2023-12. medRxiv (preprint). “Prevalence of Olfactory Dysfunction with the Omicron Variant of SARS-CoV-2: A Systematic Review and Meta-analysis.” https://doi.org/10.1101/2022.12.16.22283582 (bartheld2023prevalenceofolfactory pages 11-15, bartheld2023prevalenceofolfactory pages 1-6)
  • Gallucci et al. 2024-08. Cells. “PPAR-Mediated Bile Acid Glucuronidation: Therapeutic Targets for the Treatment of Cholestatic Liver Diseases.” https://doi.org/10.3390/cells13151296 (gallucci2024pparmediatedbileacid pages 10-11)
  • Jedlitschky et al. 1999-06. Biochemical Journal. “Cloning and characterization of a novel human olfactory UDP-glucuronosyltransferase.” https://doi.org/10.1042/bj3400837 (jedlitschky1999cloningandcharacterization pages 5-6)
  • Sneitz et al. 2009-12. Pharmacogenetics and Genomics. “Human UGT2A2 … in comparison with UGT2A1 and UGT2A3.” https://doi.org/10.1097/FPC.0b013e3283330767 (sneitz2009humanudpglucuronosyltransferaseugt2a2 pages 9-10)

References

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  2. (heydel2010udpglucuronosyltransferases(ugts)in pages 3-5): Jean-Marie Heydel, Elzbieta J Holsztynska, Arièle Legendre, Nicolas Thiebaud, Yves Artur, and Anne-Marie Le Bon. Udp-glucuronosyltransferases (ugts) in neuro-olfactory tissues: expression, regulation, and function. Drug Metabolism Reviews, 42:74-97, Jan 2010. URL: https://doi.org/10.3109/03602530903208363, doi:10.3109/03602530903208363. This article has 69 citations and is from a peer-reviewed journal.

  3. (neiers2021theodorantmetabolizing pages 6-8): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  4. (neiers2021theodorantmetabolizing pages 2-4): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  5. (heydel2010udpglucuronosyltransferases(ugts)in pages 18-19): Jean-Marie Heydel, Elzbieta J Holsztynska, Arièle Legendre, Nicolas Thiebaud, Yves Artur, and Anne-Marie Le Bon. Udp-glucuronosyltransferases (ugts) in neuro-olfactory tissues: expression, regulation, and function. Drug Metabolism Reviews, 42:74-97, Jan 2010. URL: https://doi.org/10.3109/03602530903208363, doi:10.3109/03602530903208363. This article has 69 citations and is from a peer-reviewed journal.

  6. (neiers2021theodorantmetabolizing pages 4-6): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  7. (neiers2021theodorantmetabolizing media 64d5c307): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  8. (neiers2021theodorantmetabolizing media e8c32847): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  9. (neiers2021theodorantmetabolizing media cd8ac3e6): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  10. (neiers2021theodorantmetabolizing pages 1-2): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

  11. (heydel2010udpglucuronosyltransferases(ugts)in pages 13-14): Jean-Marie Heydel, Elzbieta J Holsztynska, Arièle Legendre, Nicolas Thiebaud, Yves Artur, and Anne-Marie Le Bon. Udp-glucuronosyltransferases (ugts) in neuro-olfactory tissues: expression, regulation, and function. Drug Metabolism Reviews, 42:74-97, Jan 2010. URL: https://doi.org/10.3109/03602530903208363, doi:10.3109/03602530903208363. This article has 69 citations and is from a peer-reviewed journal.

  12. (heydel2010udpglucuronosyltransferases(ugts)in pages 12-13): Jean-Marie Heydel, Elzbieta J Holsztynska, Arièle Legendre, Nicolas Thiebaud, Yves Artur, and Anne-Marie Le Bon. Udp-glucuronosyltransferases (ugts) in neuro-olfactory tissues: expression, regulation, and function. Drug Metabolism Reviews, 42:74-97, Jan 2010. URL: https://doi.org/10.3109/03602530903208363, doi:10.3109/03602530903208363. This article has 69 citations and is from a peer-reviewed journal.

  13. (jedlitschky1999cloningandcharacterization pages 5-6): Gabriele JEDLITSCHKY, Andrew J. CASSIDY, Mark SALES, Norman PRATT, and Brian BURCHELL. Cloning and characterization of a novel human olfactory udp-glucuronosyltransferase. The Biochemical journal, 340 ( Pt 3):837-43, Jun 1999. URL: https://doi.org/10.1042/bj3400837, doi:10.1042/bj3400837. This article has 84 citations.

  14. (sneitz2009humanudpglucuronosyltransferaseugt2a2 pages 9-10): Nina Sneitz, Michael H. Court, Xiuling Zhang, Kaisa Laajanen, Karen K. Yee, Pamela Dalton, Xinxin Ding, and Moshe Finel. Human udp-glucuronosyltransferase ugt2a2: cdna construction, expression, and functional characterization in comparison with ugt2a1 and ugt2a3. Pharmacogenetics and Genomics, 19:923-934, Dec 2009. URL: https://doi.org/10.1097/fpc.0b013e3283330767, doi:10.1097/fpc.0b013e3283330767. This article has 78 citations and is from a peer-reviewed journal.

  15. (heydel2010udpglucuronosyltransferases(ugts)in pages 17-18): Jean-Marie Heydel, Elzbieta J Holsztynska, Arièle Legendre, Nicolas Thiebaud, Yves Artur, and Anne-Marie Le Bon. Udp-glucuronosyltransferases (ugts) in neuro-olfactory tissues: expression, regulation, and function. Drug Metabolism Reviews, 42:74-97, Jan 2010. URL: https://doi.org/10.3109/03602530903208363, doi:10.3109/03602530903208363. This article has 69 citations and is from a peer-reviewed journal.

  16. (heydel2010udpglucuronosyltransferases(ugts)in pages 16-17): Jean-Marie Heydel, Elzbieta J Holsztynska, Arièle Legendre, Nicolas Thiebaud, Yves Artur, and Anne-Marie Le Bon. Udp-glucuronosyltransferases (ugts) in neuro-olfactory tissues: expression, regulation, and function. Drug Metabolism Reviews, 42:74-97, Jan 2010. URL: https://doi.org/10.3109/03602530903208363, doi:10.3109/03602530903208363. This article has 69 citations and is from a peer-reviewed journal.

  17. (bartheld2023prevalenceofolfactory pages 11-15): CHRISTOPHER S VON BARTHELD and Lingchen Wang. Prevalence of olfactory dysfunction with the omicron variant of sars-cov-2: a systematic review and meta-analysis. medRxiv, Dec 2023. URL: https://doi.org/10.1101/2022.12.16.22283582, doi:10.1101/2022.12.16.22283582. This article has 83 citations.

  18. (bartheld2023prevalenceofolfactory pages 1-6): CHRISTOPHER S VON BARTHELD and Lingchen Wang. Prevalence of olfactory dysfunction with the omicron variant of sars-cov-2: a systematic review and meta-analysis. medRxiv, Dec 2023. URL: https://doi.org/10.1101/2022.12.16.22283582, doi:10.1101/2022.12.16.22283582. This article has 83 citations.

  19. (gallucci2024pparmediatedbileacid pages 10-11): Gina M. Gallucci, Colleen M. Hayes, James L. Boyer, Olivier Barbier, David N. Assis, and Nisanne S. Ghonem. Ppar-mediated bile acid glucuronidation: therapeutic targets for the treatment of cholestatic liver diseases. Cells, 13:1296, Aug 2024. URL: https://doi.org/10.3390/cells13151296, doi:10.3390/cells13151296. This article has 31 citations.

  20. (neiers2021theodorantmetabolizing pages 13-13): Fabrice Neiers, David Jarriault, Franck Menetrier, Philippe Faure, Loïc Briand, and Jean-Marie Heydel. The odorant metabolizing enzyme ugt2a1: immunolocalization and impact of the modulation of its activity on the olfactory response. PLOS ONE, 16:e0249029, Mar 2021. URL: https://doi.org/10.1371/journal.pone.0249029, doi:10.1371/journal.pone.0249029. This article has 44 citations and is from a peer-reviewed journal.

Artifacts

Citations

  1. neiers2021theodorantmetabolizing pages 6-8
  2. jedlitschky1999cloningandcharacterization pages 5-6
  3. gallucci2024pparmediatedbileacid pages 10-11
  4. neiers2021theodorantmetabolizing pages 13-13
  5. neiers2021theodorantmetabolizing pages 1-2
  6. neiers2021theodorantmetabolizing pages 4-6
  7. neiers2021theodorantmetabolizing pages 2-4
  8. bartheld2023prevalenceofolfactory pages 11-15
  9. bartheld2023prevalenceofolfactory pages 1-6
  10. https://doi.org/10.3109/03602530903208363
  11. https://doi.org/10.1371/journal.pone.0249029;
  12. https://doi.org/10.1371/journal.pone.0249029
  13. https://doi.org/10.1101/2022.12.16.22283582
  14. https://doi.org/10.3390/cells13151296
  15. https://doi.org/10.1042/bj3400837
  16. https://doi.org/10.1097/FPC.0b013e3283330767
  17. https://doi.org/10.3109/03602530903208363,
  18. https://doi.org/10.1371/journal.pone.0249029,
  19. https://doi.org/10.1042/bj3400837,
  20. https://doi.org/10.1097/fpc.0b013e3283330767,
  21. https://doi.org/10.1101/2022.12.16.22283582,
  22. https://doi.org/10.3390/cells13151296,

📄 View Raw YAML

 
id: P36510
gene_symbol: Ugt2a1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:10116
  label: Rattus norvegicus
description: 'Ugt2a1 encodes the olfactory UDP-glucuronosyltransferase (UGT-olf), a UGT2A-subfamily enzyme
  enriched in the olfactory epithelium that glucuronidates odorants and other lipophilic substrates,
  contributing to phase II biotransformation and to perireceptor odorant clearance/signal termination.
  The enzyme localizes to the plasma membrane of olfactory cilia, proximal to odorant receptors, where its
  glucuronidation activity modulates the olfactory response in a substrate-dependent manner. Its primary
  molecular function is glucuronosyltransferase activity in a xenobiotic/odorant metabolic context, with
  bile-acid glucuronidation as a non-core detoxification role.'
existing_annotations:
  - term:
      id: GO:0015020
      label: glucuronosyltransferase activity
    evidence_type: IBA
    original_reference_id: GO_REF:0000033
    review:
      summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the 
        documented core enzymatic role or its direct pathway consequence (IBA, GO_REF:0000033).
      action: ACCEPT
      reason: glucuronosyltransferase activity is directly supported by the curated function of
        Ugt2a1 and is not merely a downstream phenotype or expression response.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            UGT2A1 is a **phase II xenobiotic‑metabolizing enzyme** that catalyzes **glucuronidation**: transfer of glucuronic acid from **UDP‑glucuronic acid (UDPGA)** to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing **more hydrophilic glucuronides** that tend to be eliminated more readily.
  - term:
      id: GO:0008194
      label: UDP-glycosyltransferase activity
    evidence_type: IEA
    original_reference_id: GO_REF:0000002
    review:
      proposed_replacement_terms:
        - id: GO:0015020
          label: glucuronosyltransferase activity
      summary: UDP-glycosyltransferase activity captures part of Ugt2a1 biology, but more specific 
        replacement term(s) better represent the supported function (IEA, GO_REF:0000002).
      action: MODIFY
      reason: 'UDP-glycosyltransferase activity is too broad or imprecise for Ugt2a1; replace with the
        more specific supported term(s): GO:0015020 glucuronosyltransferase activity.'
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
  - term:
      id: GO:0015020
      label: glucuronosyltransferase activity
    evidence_type: IEA
    original_reference_id: GO_REF:0000120
    review:
      summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the 
        documented core enzymatic role or its direct pathway consequence (IEA, GO_REF:0000120).
      action: ACCEPT
      reason: glucuronosyltransferase activity is directly supported by the curated function of 
        Ugt2a1 and is not merely a downstream phenotype or expression response.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
  - term:
      id: GO:0016020
      label: membrane
    evidence_type: IEA
    original_reference_id: GO_REF:0000044
    review:
      proposed_replacement_terms:
        - id: GO:0060170
          label: ciliary membrane
      summary: membrane is too broad; immunogold EM localizes UGT2A1 to the plasma membrane of
        olfactory cilia, supporting the more specific ciliary membrane term (IEA, GO_REF:0000044).
      action: MODIFY
      reason: 'membrane is overly generic. Immunogold electron microscopy localizes UGT2A1 to the
        plasma membrane of olfactory cilia (a cell-projection/plasma membrane location proximal to
        odorant receptors), so the annotation should be upgraded to the more specific CC term
        GO:0060170 ciliary membrane.'
      supported_by:
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            Critically, immunogold EM supports localization of UGT2A1 at the **plasma membrane of olfactory cilia**—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space
  - term:
      id: GO:0006805
      label: xenobiotic metabolic process
    evidence_type: ISO
    original_reference_id: GO_REF:0000121
    review:
      summary: xenobiotic metabolic process is retained for Ugt2a1 because it matches the documented
        core enzymatic role or its direct pathway consequence (ISO, GO_REF:0000121).
      action: ACCEPT
      reason: xenobiotic metabolic process is directly supported by the curated function of Ugt2a1
        and is not merely a downstream phenotype or expression response.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            A neuro‑olfactory UGT review explicitly frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route
  - term:
      id: GO:0009608
      label: response to symbiont
    evidence_type: ISO
    original_reference_id: GO_REF:0000121
    review:
      summary: response to symbiont should not be retained for Ugt2a1 based on the combined gene 
        function and cited/source evidence (ISO, GO_REF:0000121).
      action: REMOVE
      reason: The available evidence supports Ugt2a1's curated activity rather than response to 
        symbiont; this annotation is unsupported, assigned to the wrong biological context, or too 
        misleading to keep as non-core.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
  - term:
      id: GO:0015020
      label: glucuronosyltransferase activity
    evidence_type: ISS
    original_reference_id: GO_REF:0000024
    review:
      summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the 
        documented core enzymatic role or its direct pathway consequence (ISS, GO_REF:0000024).
      action: ACCEPT
      reason: glucuronosyltransferase activity is directly supported by the curated function of 
        Ugt2a1 and is not merely a downstream phenotype or expression response.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
  - term:
      id: GO:0015020
      label: glucuronosyltransferase activity
    evidence_type: ISO
    original_reference_id: GO_REF:0000121
    review:
      summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the 
        documented core enzymatic role or its direct pathway consequence (ISO, GO_REF:0000121).
      action: ACCEPT
      reason: glucuronosyltransferase activity is directly supported by the curated function of 
        Ugt2a1 and is not merely a downstream phenotype or expression response.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
  - term:
      id: GO:0016020
      label: membrane
    evidence_type: ISS
    original_reference_id: GO_REF:0000024
    review:
      proposed_replacement_terms:
        - id: GO:0060170
          label: ciliary membrane
      summary: membrane is too broad; immunogold EM localizes UGT2A1 to the plasma membrane of
        olfactory cilia, supporting the more specific ciliary membrane term (ISS, GO_REF:0000024).
      action: MODIFY
      reason: 'membrane is overly generic. Immunogold electron microscopy localizes UGT2A1 to the
        plasma membrane of olfactory cilia (a cell-projection/plasma membrane location proximal to
        odorant receptors), so the annotation should be upgraded to the more specific CC term
        GO:0060170 ciliary membrane.'
      supported_by:
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            Critically, immunogold EM supports localization of UGT2A1 at the **plasma membrane of olfactory cilia**—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space
  - term:
      id: GO:0007606
      label: sensory perception of chemical stimulus
    evidence_type: ISO
    original_reference_id: GO_REF:0000121
    review:
      summary: sensory perception of chemical stimulus is kept as a non-core process for Ugt2a1.
        Its enzymatic activity modulates odorant availability in the perireceptor space rather than
        executing the neurological transduction cascade itself (ISO, GO_REF:0000121).
      action: KEEP_AS_NON_CORE
      reason: 'GO:0007606 is defined as a neurological process in which an organism receives a chemical
        stimulus, converts it to a molecular signal, and recognizes/characterizes it. This transduction
        cascade is executed by olfactory receptor neurons, not by a metabolic enzyme. UGT2A1
        glucuronidates odorants and thereby modulates odorant concentration in the perireceptor space
        (ex vivo electroolfactogram shows topical beta-glucuronidase selectively increases the eugenol
        response), so it is a modulator of odorant availability rather than a component of the sensory
        transduction cascade. The annotation is retained as a non-core contextual involvement rather
        than ACCEPTed as a core function. There is no GO odorant metabolic process term to MODIFY to
        (the previously suggested GO:0042545 is cell wall modification, a plant term, and GO:0052697
        xenobiotic glucuronidation is obsolete); the core metabolic role is captured by the
        xenobiotic metabolic process and glucuronosyltransferase activity annotations.'
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            counteracting UGT activity with topical **β‑glucuronidase** increased the EOG response amplitude to **eugenol** but not to **amyl acetate**, consistent with the interpretation that glucuronidation reduces effective eugenol concentration at receptors
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            In the olfactory system, such glucuronidation is part of the **perireceptor process**, i.e., local metabolism in the mucus/epithelium that shapes the concentration-time profile of odorants reaching olfactory receptors and can thereby contribute to **signal termination**
  - term:
      id: GO:0008206
      label: bile acid metabolic process
    evidence_type: ISO
    original_reference_id: GO_REF:0000121
    review:
      summary: bile acid metabolic process is retained as contextual support for Ugt2a1, but it is 
        not the core function (ISO, GO_REF:0000121).
      action: KEEP_AS_NON_CORE
      reason: bile acid metabolic process records a physiological/substrate context rather than the
        defining molecular activity of Ugt2a1. This is an ISO annotation transferred from human UGT2A1
        (P0DTE4); the supporting Falcon evidence (bile-acid glucuronidation activity) is from human
        studies, consistent with the ISO basis, and supports retention as a non-core detoxification
        process distinct from the primary olfactory role.
      supported_by:
        - reference_id: UniProtKB:P36510
          supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
            reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
            tissue specificity, and therefore may be involved in olfaction.'
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            UGT2A1 is described as **highly active in bile-acid glucuronidation**, and it notes characterization of UGT2A1 variants and disease connections (human context)
  - term:
      id: GO:0009636
      label: response to toxic substance
    evidence_type: TAS
    original_reference_id: PMID:1900353
    review:
      summary: response to toxic substance is an over-annotation for Ugt2a1; PMID:1900353 supports 
        odorant glucuronidation and olfactory signal termination rather than a toxicological 
        response process.
      action: MARK_AS_OVER_ANNOTATED
      reason: The cited paper establishes glucuronosyltransferase activity toward odorants. That
        supports the MF annotation and olfactory chemical-stimulus context, but not a broad response
        to toxic substance biological process. Falcon deep research frames nasal UGTs (including
        UGT2A1) as a protective metabolic barrier; this is a constitutive detoxification/clearance
        role rather than an inducible response-to-toxin process, reinforcing that GO:0009636 is an
        over-annotation.
      supported_by:
        - reference_id: PMID:1900353
          supporting_text: We report here the molecular cloning and expression of an
            olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows
            preference for odorants over standard UGT substrates.
          reference_section_type: ABSTRACT
        - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
          supporting_text: |-
            frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route
  - term:
      id: GO:0015020
      label: glucuronosyltransferase activity
    evidence_type: TAS
    original_reference_id: PMID:1900353
    review:
      summary: glucuronosyltransferase activity is retained for Ugt2a1 because it matches the 
        documented core enzymatic role or its direct pathway consequence (TAS, PMID:1900353).
      action: ACCEPT
      reason: glucuronosyltransferase activity is directly supported by the curated function of 
        Ugt2a1 and is not merely a downstream phenotype or expression response.
      supported_by:
        - reference_id: PMID:1900353
          supporting_text: We report here the molecular cloning and expression of an 
            olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows
            preference for odorants over standard UGT substrates.
          reference_section_type: ABSTRACT
references:
  - id: GO_REF:0000002
    title: GO reference used by source annotation pipeline
    findings:
      - statement: Source annotation pipeline provenance for Ugt2a1 annotations including 
          UDP-glycosyltransferase activity.
        supporting_text: GO_REF entry used only to trace source annotation method; biological 
          support was assessed from UniProt and cached literature where available.
        reference_section_type: TITLE
  - id: GO_REF:0000024
    title: GO reference used by source annotation pipeline
    findings:
      - statement: Source annotation pipeline provenance for Ugt2a1 annotations including 
          glucuronosyltransferase activity; membrane.
        supporting_text: GO_REF entry used only to trace source annotation method; biological 
          support was assessed from UniProt and cached literature where available.
        reference_section_type: TITLE
  - id: GO_REF:0000033
    title: GO reference used by source annotation pipeline
    findings:
      - statement: Source annotation pipeline provenance for Ugt2a1 annotations including 
          glucuronosyltransferase activity.
        supporting_text: GO_REF entry used only to trace source annotation method; biological 
          support was assessed from UniProt and cached literature where available.
        reference_section_type: TITLE
  - id: GO_REF:0000044
    title: GO reference used by source annotation pipeline
    findings:
      - statement: Source annotation pipeline provenance for Ugt2a1 annotations including membrane.
        supporting_text: GO_REF entry used only to trace source annotation method; biological 
          support was assessed from UniProt and cached literature where available.
        reference_section_type: TITLE
  - id: GO_REF:0000120
    title: GO reference used by source annotation pipeline
    findings:
      - statement: Source annotation pipeline provenance for Ugt2a1 annotations including 
          glucuronosyltransferase activity.
        supporting_text: GO_REF entry used only to trace source annotation method; biological 
          support was assessed from UniProt and cached literature where available.
        reference_section_type: TITLE
  - id: GO_REF:0000121
    title: GO reference used by source annotation pipeline
    findings:
      - statement: Source annotation pipeline provenance for Ugt2a1 annotations including bile acid 
          metabolic process; glucuronosyltransferase activity; response to symbiont; sensory 
          perception of chemical stimulus; xenobiotic metabolic process.
        supporting_text: GO_REF entry used only to trace source annotation method; biological 
          support was assessed from UniProt and cached literature where available.
        reference_section_type: TITLE
  - id: PMID:1900353
    title: Odorant signal termination by olfactory UDP glucuronosyl transferase.
    findings:
      - statement: For Ugt2a1, this publication was assessed for annotations including 
          glucuronosyltransferase activity; response to toxic substance.
        supporting_text: We report here the molecular cloning and expression of an
          olfactory-specific UGT. The olfactory enzyme, but not the one in liver microsomes, shows
          preference for odorants over standard UGT substrates.
        reference_section_type: ABSTRACT
  - id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
    title: 'Falcon (Edison Scientific) deep research report: rat Ugt2a1 (UDP-glucuronosyltransferase 2A1, UGT-olf)'
    findings:
      - statement: Ugt2a1/UGT2A1 is the olfactory UDP-glucuronosyltransferase (UGT-olf), a UGT2A
          subfamily member enriched in neuro-olfactory tissues, confirming gene identity (UniProt P36510).
        supporting_text: |-
          historically termed **UGT-olf/UGTolf**, a member of the UGT2A subfamily enriched in neuro‑olfactory tissues
        reference_section_type: OTHER
      - statement: UGT2A1 catalyzes glucuronidation, transferring glucuronic acid from UDP-glucuronic
          acid to nucleophilic acceptors to form more hydrophilic glucuronides, supporting the
          glucuronosyltransferase molecular function.
        supporting_text: |-
          UGT2A1 is a **phase II xenobiotic‑metabolizing enzyme** that catalyzes **glucuronidation**: transfer of glucuronic acid from **UDP‑glucuronic acid (UDPGA)** to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing **more hydrophilic glucuronides** that tend to be eliminated more readily.
        reference_section_type: OTHER
      - statement: Glucuronidation by UGT2A1 is part of the olfactory perireceptor process and can
          contribute to odorant signal termination, supporting the sensory-perception annotations.
        supporting_text: |-
          In the olfactory system, such glucuronidation is part of the **perireceptor process**, i.e., local metabolism in the mucus/epithelium that shapes the concentration-time profile of odorants reaching olfactory receptors and can thereby contribute to **signal termination**
        reference_section_type: OTHER
      - statement: Glucuronidated odorant metabolites fail to stimulate canonical cAMP signaling in
          olfactory cilia preparations, mechanistically linking UGT2A1 activity to reduced receptor
          activation.
        supporting_text: |-
          olfactory cilia preparations show that **glucuronidated odorant metabolites fail to stimulate canonical cAMP signaling**, consistent with a mechanism by which glucuronidation reduces receptor activation and promotes signal termination
        reference_section_type: OTHER
      - statement: Immunogold EM localizes UGT2A1 to the plasma membrane of olfactory cilia (in
          addition to sustentacular-cell ER), supporting membrane localization proximal to odorant
          receptors.
        supporting_text: |-
          Critically, immunogold EM supports localization of UGT2A1 at the **plasma membrane of olfactory cilia**—a location that is unusually proximal to odorant receptors and supports rapid metabolism in the perireceptor space
        reference_section_type: OTHER
      - statement: UGT2A1 immunolocalizes broadly in the apical olfactory epithelium including
          sustentacular cells and Bowman's glands/ducts.
        supporting_text: |-
          localize UGT2A1 broadly within the olfactory epithelium and especially in the apical region, including **sustentacular cells** and **Bowman’s glands/ducts**
        reference_section_type: OTHER
      - statement: Ex vivo electroolfactogram experiments show topical β-glucuronidase selectively
          increases the eugenol but not amyl-acetate response, giving causal in-situ evidence that
          glucuronidation modulates the olfactory response.
        supporting_text: |-
          counteracting UGT activity with topical **β‑glucuronidase** increased the EOG response amplitude to **eugenol** but not to **amyl acetate**, consistent with the interpretation that glucuronidation reduces effective eugenol concentration at receptors
        reference_section_type: OTHER
      - statement: UGT2A1 substrate scope extends beyond odorants to coumarins, drugs/xenobiotics and
          steroids (estradiol/testosterone), supporting broader xenobiotic and steroid handling.
        supporting_text: |-
          monoterpenoid alcohols** (e.g., geraniol, linalool, borneol, menthol), **coumarins** (e.g., umbelliferone derivatives), **drugs/xenobiotics** (e.g., ibuprofen, valproic acid), and **steroids** (e.g., estradiol/testosterone), supporting a role that extends beyond “odorant-only” metabolism and into broader nasal detoxification and local steroid handling
        reference_section_type: OTHER
      - statement: Nasal UGTs including UGT2A1 form a protective metabolic barrier reducing local
          toxicity and xenobiotic delivery to the brain, supporting the xenobiotic metabolic process role.
        supporting_text: |-
          frames nasal UGTs (including UGT2A1 expressed in olfactory epithelium) as part of a protective barrier that can reduce local toxicity and potentially limit delivery of xenobiotics to the brain via the nasal route
        reference_section_type: OTHER
      - statement: Human UGT2A1 is reported highly active in bile-acid glucuronidation, corroborating
          the bile acid metabolic process annotation as a non-core detoxification role.
        supporting_text: |-
          UGT2A1 is described as **highly active in bile-acid glucuronidation**, and it notes characterization of UGT2A1 variants and disease connections (human context)
        reference_section_type: OTHER
core_functions:
  - description: Ugt2a1 glucuronidates odorants and lipophilic substrates as an olfactory
      UDP-glucuronosyltransferase, contributing to perireceptor odorant clearance and signal termination.
    supported_by:
      - reference_id: UniProtKB:P36510
        supporting_text: 'FUNCTION: UDP-glucuronosyltransferase that catalyzes phase II biotransformation
          reactions. Shows a high affinity to aliphatic odorants such as citronellol as well as olfactory
          tissue specificity, and therefore may be involved in olfaction.'
      - reference_id: file:rat/Ugt2a1/Ugt2a1-deep-research-falcon.md
        supporting_text: |-
          UGT2A1 is a **phase II xenobiotic‑metabolizing enzyme** that catalyzes **glucuronidation**: transfer of glucuronic acid from **UDP‑glucuronic acid (UDPGA)** to small molecules bearing suitable nucleophilic groups (e.g., hydroxyl groups), producing **more hydrophilic glucuronides** that tend to be eliminated more readily.
    molecular_function:
      id: GO:0015020
      label: glucuronosyltransferase activity
    directly_involved_in:
      - id: GO:0006805
        label: xenobiotic metabolic process