Proposed New Ontology Terms

nicotine glucoside hydrolase activity

Definition: Catalysis of the hydrolysis of a nicotine-pathway glucoside intermediate to release nicotine and beta-D-glucose during the late steps of nicotine biosynthesis.

Justification: The recent nicotine pathway paper resolves a specialized beta-GD1/NicGH function that is not captured by the generic beta-glucosidase activity term.

Parent term: beta-glucosidase activity

Supporting Evidence:

file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md : The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0004553 hydrolase activity, hydrolyzing O-glycosyl compounds	IEA GO_REF:0000120	MODIFY	Summary: This parent hydrolase term should be collapsed to the more specific beta-glucosidase annotation. Reason: GO:0008422 captures the relevant GH1 catalytic specificity more directly. Proposed replacements: beta-glucosidase activity
GO:0005975 carbohydrate metabolic process	IEA GO_REF:0000002	MARK AS OVER ANNOTATED	Summary: This broad process term is too generic to express the pathway-specific conclusion. Reason: The more informative biology is a nicotine-pathway glucoside hydrolase role rather than generic carbohydrate metabolism.
GO:0008422 beta-glucosidase activity	IEA GO_REF:0000118	ACCEPT	Summary: This is the core catalytic annotation for the BGLU18_6 candidate. Reason: UniProt and GH1 family assignment support beta-glucosidase chemistry, and the pathway paper makes beta-GD1 the late nicotine hydrolase. Supporting Evidence: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.
GO:0042179 nicotine biosynthetic process	TAS file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md	NEW	Summary: BGLU18_6 should be added as the leading nicotine-pathway beta-glucosidase candidate. Reason: The paper identifies beta-GD1/NicGH as a core late hydrolase and the mapping pass places BGLU18_6 as the best current attenuata ortholog. Supporting Evidence: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md The 2026-04-05 mapping dive assigns NaBGL1 to BGLU18_6 / A0A1J6KFZ7 as the best current sequence-backed NICAT ortholog to tobacco beta-GD1, and explicitly demotes the older BGLU42 launch to a weaker historical comparator.

Core Functions

BGLU18_6 is the best current NICAT candidate for the NicGH/beta-GD1 step that hydrolyzes a late nicotine glucoside intermediate.

Molecular Function:

beta-glucosidase activity

Directly Involved In:

nicotine biosynthetic process

Supporting Evidence:

file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.

References

GO_REF:0000002

Gene Ontology annotation through association of InterPro records with GO terms

GO_REF:0000118

TreeGrafter-generated GO annotations

GO_REF:0000120

Combined Automated Annotation using Multiple IEA Methods

file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-uniprot.txt

UniProt entry A0A1J6KFZ7 for Nicotiana attenuata BGLU18_6

BGLU18_6 is a glycosyl hydrolase family 1 beta-glucosidase

"DE SubName: Full=Beta-glucosidase 18"
UniProt assigns beta-glucosidase activity to BGLU18_6

"DR GO; GO:0008422; F:beta-glucosidase activity; IEA:TreeGrafter."

file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md

NaBGL1 BGLU18_6 candidate notes

beta-GD1 is the NicGH hydrolase in the reconstituted late nicotine pathway

"The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade."
BGLU18_6 is the best current sequence-backed NICAT ortholog to tobacco beta-GD1

"The 2026-04-05 mapping dive assigns NaBGL1 to BGLU18_6 / A0A1J6KFZ7 as the best current sequence-backed NICAT ortholog to tobacco beta-GD1, and explicitly demotes the older BGLU42 launch to a weaker historical comparator."

file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-deep-research-falcon.md

Deep research report on NaBGL1/BGLU18_6 (Falcon/Edison Scientific Literature)

No primary publication directly characterizes A0A1J6KFZ7 / BGLU18_6; the most defensible annotation rests on GH1 family inference (retaining double-displacement mechanism, conserved NEP/TENG catalytic glutamates, (alpha/beta)8 TIM barrel fold) plus the nicotine-pathway notes which place this candidate as the attenuata ortholog of the experimentally defined beta-GD1/NicGH in the A622-MATE1-beta-GD1 cluster.

Suggested Experiments

Experiment: Reconstitute BGLU18_6 with the UGT1-A622-BBL module and test hydrolysis of the resulting late nicotine glucosides.

Hypothesis: BGLU18_6 is the principal attenuata NicGH ortholog and efficiently hydrolyzes the pathway nicotine glucoside.

Type: pathway reconstitution assay

Experiment: Knock out the BGLU18_6 candidate and measure nicotine glucoside accumulation together with nicotine depletion after induction.

Hypothesis: Loss of BGLU18_6 will cause buildup of late glucosylated intermediates and reduce nicotine output.

Type: genetic perturbation plus metabolite profiling

Deep Research

Falcon

(NaBGL1_candidate_BGLU18_6-deep-research-falcon.md)

this with annotations you find in gene/protein databases, but these can be outdated or inaccurate. Falcon Edison Scientific Literature 25 citations 2 artifacts 2026-05-22T22:48:01.183714

Edison artifact artifact-00 (text/markdown)

## Context ID: pqac-00000005 I have located the requested figures showing the structural aspects of the GH1 beta-glucosidases ThBgl1 and ThBgl2: - **Figure 5 (p (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: Functional annotation of Nicotiana attenuata BGLU18_6 (UniProt A0A1J6KFZ7)

0) Executive summary and identity verification (critical)

The target protein is specified (by UniProt accession provided in the prompt) as Nicotiana attenuata (coyote tobacco) “Beta-glucosidase 18” with gene name BGLU18_6 / ORF A4A49_57285, and annotated to glycosyl hydrolase family 1 (GH1; PF00232).

A targeted literature search using the exact identifiers A0A1J6KFZ7, BGLU18_6, and A4A49_57285 did not retrieve any paper in the current corpus that directly studies or even mentions this specific N. attenuata protein; therefore, any functional assignment below must be treated as GH1-family inference and must not be conflated with Arabidopsis “BGLU18” (a different gene) that appears in proteomics datasets under the same symbol (niehl2013labelfreequantitativeproteomic pages 5-6).

The artifact table below summarizes what can and cannot be supported from the retrieved evidence.

Claim/annotation item	Evidence type (direct for this gene vs inference from GH1 family vs related gene in other species)	Key details (reaction, motifs, localization, pathway)	Best supporting source (citation id)	Publication year	URL (if in evidence)
No direct literature found for Nicotiana attenuata BGLU18_6 / UniProt A0A1J6KFZ7 / ORF A4A49_57285 in retrieved papers	Direct search result for this exact gene: none	No retrieved paper directly mentioned the accession, gene symbol, or ORF; functional annotation must therefore rely on UniProt/domain assignment plus cautious family-level inference	(florindo2018structuralinsightsinto pages 12-15)	2018	https://doi.org/10.1016/j.nbt.2017.08.012
Protein is very likely a GH1 beta-glucosidase	Inference from GH1 family/domain assignment	GH1 beta-glucosidases hydrolyze β-glucosidic bonds between carbohydrate units or between a carbohydrate and an aglycone; this matches the UniProt description “Beta-glucosidase 18” and GH1/PF00232 domain assignment	(cho2020enhancedbiomassyield pages 1-3)	2020	https://doi.org/10.3390/biom10050806
Likely catalytic mechanism is retaining double-displacement hydrolysis using two catalytic glutamates	Inference from GH1 family	GH1 enzymes use a Koshland retaining mechanism with one glutamate as catalytic acid/base and one as nucleophile, proceeding through a glycosyl-enzyme intermediate	(ehrenreich2021sitedirectedmutagenesisstudies pages 13-16)	2021
Expected conserved catalytic motifs/residues include NEP/TXNEP and TENG/related motif containing the two catalytic glutamates	Inference from GH1 family	GH1 beta-glucosidases commonly contain conserved motifs harboring the catalytic glutamates; examples include NEP and TENG, or broader TXNEP/TFNEP-like motifs used to identify GH1 active sites	(liew2018purificationandcharacterization pages 6-8, ehrenreich2021sitedirectedmutagenesisstudies pages 13-16)	2018; 2021	https://doi.org/10.1016/j.ijbiomac.2018.04.156
Expected structural fold is a canonical (α/β)8 TIM barrel	Inference from GH1 family	Structural studies of GH1 beta-glucosidases show the active site embedded in a TIM-barrel fold; catalytic glutamates occupy conserved positions in the barrel architecture	(florindo2018structuralinsightsinto pages 12-15, florindo2018structuralinsightsinto media a919e2b1)	2018	https://doi.org/10.1016/j.nbt.2017.08.012
Substrate specificity cannot be assigned specifically for BGLU18_6, but GH1 enzymes often range from aryl-β-glucosides to cellobiose and broader heterosides	Inference from GH1 family	GH1 beta-glucosidases are often classified as aryl-β-glucosidases, true cellobiases, or broad-specificity enzymes; therefore BGLU18_6 may act on small glucosides, but exact substrate must be experimentally determined	(liew2018purificationandcharacterization pages 6-8)	2018	https://doi.org/10.1016/j.ijbiomac.2018.04.156
A plausible biological role is activation of defense or specialized metabolites by deglycosylation	Related gene/function in plants and microbes; cautious inference	Plant beta-glucosidases can activate chemical defense compounds and release active metabolites from conjugates; in a host-pathogen context, beta-glucosidase hydrolysis of scopolin releases scopoletin, illustrating how glucoside cleavage can alter defense chemistry	(cho2020enhancedbiomassyield pages 1-3, deflandre2022structureandfunction pages 1-2)	2020; 2022	https://doi.org/10.3390/biom10050806; https://doi.org/10.1128/mbio.00935-22
Another plausible pathway context is phytohormone or stored-metabolite activation rather than primary cellulose digestion	Inference from plant GH1 functions	Plant beta-glucosidases are reported to release active phytohormones from conjugates and to activate defense chemistry; these roles are more consistent with many plant GH1 enzymes than bulk cellulose catabolism alone	(cho2020enhancedbiomassyield pages 1-3)	2020	https://doi.org/10.3390/biom10050806
Cellular localization remains unresolved for this exact gene	No direct evidence for this gene; limited family-level inference	Retrieved evidence did not identify subcellular localization for BGLU18_6; because plant GH1 beta-glucosidases can occur in multiple compartments, localization should be treated as unknown until sequence-based prediction or experiment confirms it	(cho2020enhancedbiomassyield pages 1-3)	2020	https://doi.org/10.3390/biom10050806
Active-site microenvironment can strongly influence substrate preference and hydrolysis vs transglycosylation	Inference from GH1 family structure-function studies	Comparative GH1 structures show that local pocket residues and water access alter glycone/aglycone binding and reaction outcome, implying that sequence-level family membership alone is insufficient to assign precise substrate specificity to BGLU18_6	(florindo2018structuralinsightsinto pages 12-15, florindo2018structuralinsightsinto media 92ab043b, florindo2018structuralinsightsinto media b52681d9)	2018	https://doi.org/10.1016/j.nbt.2017.08.012

Table: This table summarizes the available evidence and cautious inferences for functional annotation of Nicotiana attenuata BGLU18_6 (A0A1J6KFZ7). It highlights the absence of direct literature for the exact gene and shows which annotation items are supported only by GH1 family knowledge or related beta-glucosidase studies.

1) Key concepts and definitions (current understanding)

1.1 What “β-glucosidase (GH1)” means

GH1 β-glucosidases are glycoside hydrolases that cleave β-glucosidic bonds, releasing terminal glucose from (i) oligosaccharides such as cellobiose/cello-oligosaccharides, or (ii) small-molecule glucosides (“heterosides”) where glucose is linked to an aglycone (cho2020enhancedbiomassyield pages 1-3, liew2018purificationandcharacterization pages 6-8).

1.2 Catalytic mechanism (retaining double-displacement) and active-site architecture

Across GH1 enzymes, catalysis generally follows a retaining (Koshland) double-displacement mechanism using two conserved catalytic glutamate residues: one serves as the nucleophile forming a glycosyl–enzyme intermediate, and the other serves as the general acid/base (ehrenreich2021sitedirectedmutagenesisstudies pages 13-16). Structurally, GH1 β-glucosidases typically adopt a classical (α/β)8 TIM-barrel fold, with the two catalytic glutamates positioned in conserved regions of the barrel active-site cleft (florindo2018structuralinsightsinto pages 12-15).

Multiple GH1 studies report conserved sequence motifs (often summarized as NEP/TXNEP-type and TENG-type regions) that contain these catalytic glutamates and are used for GH1 identification/annotation (liew2018purificationandcharacterization pages 6-8, ehrenreich2021sitedirectedmutagenesisstudies pages 13-16). Because A0A1J6KFZ7 is annotated as GH1 in the prompt, the most defensible mechanistic inference is that it uses this canonical GH1 two-glutamate, retaining mechanism.

2) Functional hypotheses for N. attenuata BGLU18_6 (A0A1J6KFZ7)

2.1 Most defensible primary biochemical function (family-level inference)

Likely reaction class: hydrolysis of β-D-glucosides (glycoside + H2O → aglycone + D-glucose), consistent with GH1 β-glucosidase chemistry (cho2020enhancedbiomassyield pages 1-3, ehrenreich2021sitedirectedmutagenesisstudies pages 13-16).

Substrate specificity: cannot be assigned to BGLU18_6 specifically from current evidence. GH1 enzymes span (at least) aryl-β-glucosides, “true” cellobiases, and broad-specificity enzymes (liew2018purificationandcharacterization pages 6-8). Structural work shows that relatively small changes in the active-site pocket and solvent accessibility can shift reaction outcomes (hydrolysis vs transglycosylation) and alter substrate preferences, making “GH1” alone insufficient to predict the physiological substrate of BGLU18_6 (florindo2018structuralinsightsinto pages 12-15).

2.2 Plausible biological roles in plants (general β-glucosidase roles)

Plant β-glucosidases are widely implicated in (i) releasing active phytohormones from conjugated storage forms, (ii) contributing to lignification intermediates, (iii) degrading endosperm cell walls during germination, and (iv) activating chemical defense compounds by deglucosylation (cho2020enhancedbiomassyield pages 1-3). These roles provide plausible hypotheses for N. attenuata BGLU18_6, but they are not direct evidence.

3) Recent developments (prioritizing 2023–2024) relevant to functional annotation

3.1 2023: Quantitative evidence that plant β-glucosidases can control active antimicrobial coumarin levels

A 2023 Plant Physiology study in apple linked a specific plant β-glucosidase (MdBGLU40) to accumulation of coumarin (1,2-benzopyrone) and to increased resistance to Cytospora mali under high potassium (HK) status (publication date: Mar 2023; URL: https://doi.org/10.1093/plphys/kiad184) (du2023sufficientcoumarinaccumulation pages 1-2).

Key quantitative results relevant to GH1 functional logic:
- Potassium status was shifted from LK 4.30 g/kg to HK 9.30 g/kg, which increased resistance; blocking K channels abolished resistance (du2023sufficientcoumarinaccumulation pages 1-2).
- Multi-omics implicated phenylpropanoid reprogramming, reporting “increases of 18 antifungal chemicals” (du2023sufficientcoumarinaccumulation pages 1-2).
- Of 45 tested metabolites, 18 inhibited C. mali growth (du2023sufficientcoumarinaccumulation pages 11-13).
- Coumarin at HK physiological concentrations (191.2 and 245.0 µg/g) almost completely inhibited mycelial growth at 4 dpi (du2023sufficientcoumarinaccumulation pages 11-13).
- MdBGLU40 upregulation (~13.1-fold) in HK tissue was reported, and functional perturbations supported causality: overexpression increased coumarin to 172.6 ± 10.5 µg/g (vs 60.4 ± 9.5 µg/g in LK-mock) and restored resistance, while RNAi reduced MdBGLU40 expression by ~68%, lowering coumarin to 35.3 ± 8.9 µg/g and increasing lesions (e.g., 2.0 ± 0.1 cm vs 0.8 ± 0.2 cm at 4 dpi) (du2023sufficientcoumarinaccumulation pages 11-13, du2023sufficientcoumarinaccumulation pages 13-14).

Although this is not N. attenuata BGLU18_6, it is authoritative, quantitative evidence that plant β-glucosidases can be decisive “hub” enzymes that activate defense chemistry by deglycosylation steps (du2023sufficientcoumarinaccumulation pages 11-13, du2023sufficientcoumarinaccumulation pages 1-2).

3.2 2024: Tobacco transcriptomics link glycoside-hydrolase genes to immunity/metabolic reprogramming

A 2024 Frontiers in Plant Science transcriptome study in tobacco (publication date: Mar 2024; URL: https://doi.org/10.3389/fpls.2024.1338169) reported broad metabolic and signaling changes when nicotine biosynthesis regulators (NtERF189/199; NIC loci) were disrupted, including induction of carbohydrate/glycoside metabolism pathways (song2024comparativetranscriptomeanalysis pages 8-9).

Notable points for contextualizing GH enzymes:
- The paper reports induction of genes annotated as glycoside hydrolases (example given: “glucan endo-1,3-beta-glucosidase 5”) among upregulated genes in nicotine-deficient plants, alongside KEGG enrichments including starch and sucrose metabolism and amino sugar and nucleotide sugar metabolism (song2024comparativetranscriptomeanalysis pages 8-9).
- Differential expression thresholds were defined as |log2FC| ≥ 1, and the authors report 75 AP2/ERF TFs differentially expressed (7 up, 68 down), indicating global rewiring of stress/defense-associated transcriptional programs (song2024comparativetranscriptomeanalysis pages 8-9).

This study does not identify BGLU18_6, but it supports the broader idea that glycoside hydrolases are engaged during immunity-related metabolic reprogramming in Nicotiana species (song2024comparativetranscriptomeanalysis pages 8-9).

4) Structural/biochemical evidence that motivates caution in assigning specific substrates to BGLU18_6

A high-resolution structure-function analysis of two GH1 enzymes (publication date: Jan 2018; URL: https://doi.org/10.1016/j.nbt.2017.08.012) shows how small active-site differences influence whether GH1 enzymes primarily hydrolyze or transglycosylate and can even shift functional class (cellobiase-like vs β-fucosidase-like) (florindo2018structuralinsightsinto pages 12-15).

The retrieved figure panels highlight:
- The canonical TIM-barrel fold of GH1 β-glucosidases (florindo2018structuralinsightsinto media a919e2b1).
- Structural alignment of active-site residues between two GH1 enzymes (florindo2018structuralinsightsinto media 92ab043b).
- The catalytic glutamates and differing water accessibility/density that correlate with hydrolysis vs transglycosylation behavior (florindo2018structuralinsightsinto media b52681d9).

These results support an “expert” interpretation that family membership (GH1) is reliable for mechanism, but not for physiological substrate without direct experimentation (florindo2018structuralinsightsinto pages 12-15, florindo2018structuralinsightsinto media b52681d9).

5) Cellular localization: what can be said for BGLU18_6

No direct localization evidence for N. attenuata A0A1J6KFZ7 was found in the retrieved corpus. More generally, plant β-glucosidases can act in diverse compartments, and engineering work demonstrates that targeting β-glucosidase activity to organelles such as chloroplasts and vacuoles is feasible and impactful (cho2020enhancedbiomassyield pages 1-3). Therefore, the localization of BGLU18_6 should be treated as currently unknown until (i) sequence-level targeting predictions (signal peptide/transit peptide) are performed for A0A1J6KFZ7, or (ii) experimental localization (e.g., fluorescent fusion) is reported.

6) Current applications and real-world implementations (β-glucosidases, including in Nicotiana)

6.1 Plant engineering for biomass saccharification (industrial biotechnology)

A 2020 study in Biomolecules (publication date: May 2020; URL: https://doi.org/10.3390/biom10050806) expressed a thermostable β-glucosidase (BglB from Thermotoga maritima) in transgenic tobacco targeted to chloroplasts and vacuoles, reporting:
- 52% higher biomass yield
- 92% higher saccharification
- 36% shorter life cycle compared to wild-type (cho2020enhancedbiomassyield pages 1-3)

This is not BGLU18_6, but it is a concrete Nicotiana implementation showing how β-glucosidase activity can be deployed in planta for real-world biomass processing outcomes (cho2020enhancedbiomassyield pages 1-3).

6.2 Defense chemistry activation by glucoside hydrolysis (conceptual implementation)

Microbial β-glucosidase work provides a mechanistic example of how glucoside cleavage can modulate plant–microbe interactions: hydrolysis of the plant heteroside scopolin by a β-glucosidase releases scopoletin, which inhibits a microbial virulence factor in Streptomyces scabiei (publication date: Aug 2022; URL: https://doi.org/10.1128/mbio.00935-22) (deflandre2022structureandfunction pages 1-2). This supports a broadly accepted defense-activation paradigm applicable to plant GH1 enzymes, including a plausible hypothesis for N. attenuata BGLU18_6.

7) Gene symbol ambiguity and “BGLU18” in the literature (why this matters here)

A proteomics study in Arabidopsis thaliana (publication date: May 2013; URL: https://doi.org/10.1021/pr3010698) lists BGLU18 with locus AT1G52400 (also “BGL1, ATBG1”), and reports it as a reproducibly changed protein in systemic tissue after mock/wounding versus virus conditions (niehl2013labelfreequantitativeproteomic pages 5-6). This underscores that “BGLU18” can refer to a well-known Arabidopsis gene and should not be taken as evidence for N. attenuata BGLU18_6.

8) Recommended next steps to turn this into a high-confidence functional annotation (evidence-generating)

Because no direct experimental literature was found for A0A1J6KFZ7 in the retrieved corpus, the most direct ways to resolve substrate specificity and in vivo role are:
1. Sequence-based checks on A0A1J6KFZ7: confirm presence/positions of GH1 catalytic glutamate motifs (NEP/TXNEP and TENG-like regions) and assess N-terminus for signal/transit peptides (mechanistic expectations supported by GH1 literature) (liew2018purificationandcharacterization pages 6-8, ehrenreich2021sitedirectedmutagenesisstudies pages 13-16).
2. Heterologous expression and substrate panel assays (pNP-β-glucoside, cellobiose, and candidate Nicotiana defense glucosides) to directly determine substrate specificity; structural evidence shows this is necessary because small pocket differences can drive large functional changes (florindo2018structuralinsightsinto pages 12-15).
3. In planta perturbation (VIGS/CRISPR or overexpression in N. attenuata) combined with metabolomics (especially phenylpropanoids/coumarins and other glucoside–aglycone pairs), inspired by the causal design used for MdBGLU40 and coumarin resistance (du2023sufficientcoumarinaccumulation pages 11-13, du2023sufficientcoumarinaccumulation pages 13-14).

9) Conclusion

Within the current retrieved literature set, there is no direct study of N. attenuata BGLU18_6 / UniProt A0A1J6KFZ7, so the best-supported annotation is that it is a GH1 retaining β-glucosidase with the canonical TIM-barrel fold and two catalytic glutamates in conserved motifs (ehrenreich2021sitedirectedmutagenesisstudies pages 13-16, florindo2018structuralinsightsinto pages 12-15). Its physiological substrate(s), pathway placement, and subcellular localization remain unresolved and should be treated as hypotheses rather than facts. Recent (2023–2024) plant studies reinforce that β-glucosidases can act as decisive enzymes in defense/specialized-metabolism activation (e.g., coumarin-based resistance under high K) and that glycoside hydrolase genes participate in Nicotiana immunity-related metabolic reprogramming, motivating targeted experimental validation of BGLU18_6 in N. attenuata (du2023sufficientcoumarinaccumulation pages 11-13, du2023sufficientcoumarinaccumulation pages 1-2, song2024comparativetranscriptomeanalysis pages 8-9).

References

(niehl2013labelfreequantitativeproteomic pages 5-6): Annette Niehl, Zhe Jenny Zhang, Martin Kuiper, Scott C. Peck, and Manfred Heinlein. Label-free quantitative proteomic analysis of systemic responses to local wounding and virus infection in arabidopsis thaliana. Journal of proteome research, 12 6:2491-503, May 2013. URL: https://doi.org/10.1021/pr3010698, doi:10.1021/pr3010698. This article has 25 citations and is from a peer-reviewed journal.
(florindo2018structuralinsightsinto pages 12-15): Renata N. Florindo, Valquiria P. Souza, Hemily S. Mutti, Cesar Camilo, Lívia Regina Manzine, Sandro R. Marana, Igor Polikarpov, and Alessandro S. Nascimento. Structural insights into β-glucosidase transglycosylation based on biochemical, structural and computational analysis of two gh1 enzymes from trichoderma harzianum. New biotechnology, 40 Pt B:218-227, Jan 2018. URL: https://doi.org/10.1016/j.nbt.2017.08.012, doi:10.1016/j.nbt.2017.08.012. This article has 55 citations and is from a peer-reviewed journal.
(cho2020enhancedbiomassyield pages 1-3): Eun Jin Cho, Quynh Anh Nguyen, Yoon Gyo Lee, Younho Song, Bok Jae Park, and Hyeun-Jong Bae. Enhanced biomass yield of and saccharification in transgenic tobacco over-expressing β-glucosidase. Biomolecules, 10:806, May 2020. URL: https://doi.org/10.3390/biom10050806, doi:10.3390/biom10050806. This article has 11 citations.
(ehrenreich2021sitedirectedmutagenesisstudies pages 13-16): CL Ehrenreich. Site-directed mutagenesis studies on a novel dual domain β-galactosidase/β-glucosidase open reading frame identified from a dairy run-off metagenome. Unknown journal, 2021.
(liew2018purificationandcharacterization pages 6-8): Kok Jun Liew, Lily Lim, Hui Ying Woo, Kok-Gan Chan, Mohd Shahir Shamsir, and Kian Mau Goh. Purification and characterization of a novel gh1 beta-glucosidase from jeotgalibacillus malaysiensis. International journal of biological macromolecules, 115:1094-1102, Aug 2018. URL: https://doi.org/10.1016/j.ijbiomac.2018.04.156, doi:10.1016/j.ijbiomac.2018.04.156. This article has 63 citations and is from a peer-reviewed journal.
(florindo2018structuralinsightsinto media a919e2b1): Renata N. Florindo, Valquiria P. Souza, Hemily S. Mutti, Cesar Camilo, Lívia Regina Manzine, Sandro R. Marana, Igor Polikarpov, and Alessandro S. Nascimento. Structural insights into β-glucosidase transglycosylation based on biochemical, structural and computational analysis of two gh1 enzymes from trichoderma harzianum. New biotechnology, 40 Pt B:218-227, Jan 2018. URL: https://doi.org/10.1016/j.nbt.2017.08.012, doi:10.1016/j.nbt.2017.08.012. This article has 55 citations and is from a peer-reviewed journal.
(deflandre2022structureandfunction pages 1-2): Benoit Deflandre, Cédric Jadot, Sören Planckaert, Noémie Thiébaut, Nudzejma Stulanovic, Raphaël Herman, Bart Devreese, Frédéric Kerff, and Sébastien Rigali. Structure and function of bcpe2, the most promiscuous gh3-family glucose scavenging beta-glucosidase. Aug 2022. URL: https://doi.org/10.1128/mbio.00935-22, doi:10.1128/mbio.00935-22. This article has 16 citations and is from a domain leading peer-reviewed journal.
(florindo2018structuralinsightsinto media 92ab043b): Renata N. Florindo, Valquiria P. Souza, Hemily S. Mutti, Cesar Camilo, Lívia Regina Manzine, Sandro R. Marana, Igor Polikarpov, and Alessandro S. Nascimento. Structural insights into β-glucosidase transglycosylation based on biochemical, structural and computational analysis of two gh1 enzymes from trichoderma harzianum. New biotechnology, 40 Pt B:218-227, Jan 2018. URL: https://doi.org/10.1016/j.nbt.2017.08.012, doi:10.1016/j.nbt.2017.08.012. This article has 55 citations and is from a peer-reviewed journal.
(florindo2018structuralinsightsinto media b52681d9): Renata N. Florindo, Valquiria P. Souza, Hemily S. Mutti, Cesar Camilo, Lívia Regina Manzine, Sandro R. Marana, Igor Polikarpov, and Alessandro S. Nascimento. Structural insights into β-glucosidase transglycosylation based on biochemical, structural and computational analysis of two gh1 enzymes from trichoderma harzianum. New biotechnology, 40 Pt B:218-227, Jan 2018. URL: https://doi.org/10.1016/j.nbt.2017.08.012, doi:10.1016/j.nbt.2017.08.012. This article has 55 citations and is from a peer-reviewed journal.
(du2023sufficientcoumarinaccumulation pages 1-2): Youwei Du, Hongchen Jia, Zi Yang, Shuanghong Wang, Yuanyuan Liu, Huiya Ma, Xiaofei Liang, Bo Wang, Mingqi Zhu, Yanan Meng, Mark L Gleason, Tom Hsiang, Sadia Noorin, Rong Zhang, and Guangyu Sun. Sufficient coumarin accumulation improves apple resistance to cytospora mali under high-potassium status. Plant Physiology, 192:1396-1419, Mar 2023. URL: https://doi.org/10.1093/plphys/kiad184, doi:10.1093/plphys/kiad184. This article has 38 citations and is from a highest quality peer-reviewed journal.
(du2023sufficientcoumarinaccumulation pages 11-13): Youwei Du, Hongchen Jia, Zi Yang, Shuanghong Wang, Yuanyuan Liu, Huiya Ma, Xiaofei Liang, Bo Wang, Mingqi Zhu, Yanan Meng, Mark L Gleason, Tom Hsiang, Sadia Noorin, Rong Zhang, and Guangyu Sun. Sufficient coumarin accumulation improves apple resistance to cytospora mali under high-potassium status. Plant Physiology, 192:1396-1419, Mar 2023. URL: https://doi.org/10.1093/plphys/kiad184, doi:10.1093/plphys/kiad184. This article has 38 citations and is from a highest quality peer-reviewed journal.
(du2023sufficientcoumarinaccumulation pages 13-14): Youwei Du, Hongchen Jia, Zi Yang, Shuanghong Wang, Yuanyuan Liu, Huiya Ma, Xiaofei Liang, Bo Wang, Mingqi Zhu, Yanan Meng, Mark L Gleason, Tom Hsiang, Sadia Noorin, Rong Zhang, and Guangyu Sun. Sufficient coumarin accumulation improves apple resistance to cytospora mali under high-potassium status. Plant Physiology, 192:1396-1419, Mar 2023. URL: https://doi.org/10.1093/plphys/kiad184, doi:10.1093/plphys/kiad184. This article has 38 citations and is from a highest quality peer-reviewed journal.
(song2024comparativetranscriptomeanalysis pages 8-9): Zhongbang Song, Ruixue Wang, Hongbo Zhang, Zhijun Tong, Cheng Yuan, Yong Li, Changjun Huang, Lu Zhao, Yuehu Wang, Yingtong Di, and Xueyi Sui. Comparative transcriptome analysis reveals nicotine metabolism is a critical component for enhancing stress response intensity of innate immunity system in tobacco. Frontiers in Plant Science, Mar 2024. URL: https://doi.org/10.3389/fpls.2024.1338169, doi:10.3389/fpls.2024.1338169. This article has 4 citations.

Artifacts

Edison artifact artifact-00

Citations

niehl2013labelfreequantitativeproteomic pages 5-6
florindo2018structuralinsightsinto pages 12-15
cho2020enhancedbiomassyield pages 1-3
ehrenreich2021sitedirectedmutagenesisstudies pages 13-16
liew2018purificationandcharacterization pages 6-8
du2023sufficientcoumarinaccumulation pages 1-2
du2023sufficientcoumarinaccumulation pages 11-13
song2024comparativetranscriptomeanalysis pages 8-9
deflandre2022structureandfunction pages 1-2
du2023sufficientcoumarinaccumulation pages 13-14
https://doi.org/10.1016/j.nbt.2017.08.012
https://doi.org/10.3390/biom10050806
https://doi.org/10.1016/j.ijbiomac.2018.04.156
https://doi.org/10.3390/biom10050806;
https://doi.org/10.1128/mbio.00935-22
https://doi.org/10.1093/plphys/kiad184
https://doi.org/10.3389/fpls.2024.1338169
https://doi.org/10.1021/pr3010698
https://doi.org/10.1021/pr3010698,
https://doi.org/10.1016/j.nbt.2017.08.012,
https://doi.org/10.3390/biom10050806,
https://doi.org/10.1016/j.ijbiomac.2018.04.156,
https://doi.org/10.1128/mbio.00935-22,
https://doi.org/10.1093/plphys/kiad184,
https://doi.org/10.3389/fpls.2024.1338169,

📚 Additional Documentation

Notes

(NaBGL1_candidate_BGLU18_6-notes.md)

NaBGL1_candidate_BGLU18_6 Notes

UniProt curates A0A1J6KFZ7 as BGLU18_6, a glycosyl hydrolase family 1 beta-glucosidase. [file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-uniprot.txt "DE SubName: Full=Beta-glucosidase 18"; "CC -!- SIMILARITY: Belongs to the glycosyl hydrolase 1 family."; "DR GO; GO:0008422; F:beta-glucosidase activity; IEA:TreeGrafter."]
The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade. [file:projects/NICOTINE_BIOSYNTHESIS/biorxiv-nicotine-glucosylation-notes.md "The paper identifies an A622-MATE1-beta-GD1 gene cluster in tobacco, plus a homeologous A622L-MATE2-beta-GD2 cluster; these clustered genes are root enriched and tightly co-expressed with known nicotine biosynthesis genes."; "The authors reconstitute a four-enzyme nicotine synthase cascade in vitro using UGT1, A622, BBLa, and beta-GD1 together with nicotinic acid, N-methylpyrrolinium, UDP-glucose, and NADPH, producing (S)-nicotine."; "beta-GD1 = NicGH, a nicotine glucoside hydrolase"]
The 2026-04-05 mapping dive assigns NaBGL1 to BGLU18_6 / A0A1J6KFZ7 as the best current sequence-backed NICAT ortholog to tobacco beta-GD1, and explicitly demotes the older BGLU42 launch to a weaker historical comparator. [file:projects/NICOTINE_BIOSYNTHESIS.md "NaBGL1 -> BGLU18_6 / A0A1J6KFZ7"; "The already-launched NaBGL1_candidate_BGLU42 row should now be treated as a weaker historical comparator, not the best orthology anchor for the paper's beta-GD genes."]

📄 View Raw YAML

id: A0A1J6KFZ7
gene_symbol: NaBGL1_candidate_BGLU18_6
product_type: PROTEIN
status: DRAFT
aliases:
- BGLU18_6
- NaBGL1
taxon:
  id: NCBITaxon:49451
  label: Nicotiana attenuata
description: >-
  NaBGL1_candidate_BGLU18_6 is the best current NICAT mapping for the beta-GD1/NicGH
  late hydrolase step that releases nicotine from a glucosylated intermediate.
  The recent pathway paper mechanistically secures beta-GD1 as a core late enzyme,
  and the mapping dive now makes BGLU18_6 the strongest attenuata orthology anchor
  for that role.
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000118
  title: TreeGrafter-generated GO annotations
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-uniprot.txt
  title: UniProt entry A0A1J6KFZ7 for Nicotiana attenuata BGLU18_6
  findings:
  - statement: BGLU18_6 is a glycosyl hydrolase family 1 beta-glucosidase
    supporting_text: 'DE   SubName: Full=Beta-glucosidase 18'
    reference_section_type: DATABASE_ENTRY
  - statement: UniProt assigns beta-glucosidase activity to BGLU18_6
    supporting_text: 'DR   GO; GO:0008422; F:beta-glucosidase activity; IEA:TreeGrafter.'
    reference_section_type: DATABASE_ENTRY
- id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
  title: NaBGL1 BGLU18_6 candidate notes
  findings:
  - statement: beta-GD1 is the NicGH hydrolase in the reconstituted late nicotine pathway
    supporting_text: The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.
    reference_section_type: LITERATURE_REVIEW
  - statement: BGLU18_6 is the best current sequence-backed NICAT ortholog to tobacco beta-GD1
    supporting_text: The 2026-04-05 mapping dive assigns NaBGL1 to BGLU18_6 / A0A1J6KFZ7 as the best current sequence-backed NICAT ortholog to tobacco beta-GD1, and explicitly demotes the older BGLU42 launch to a weaker historical comparator.
    reference_section_type: LITERATURE_REVIEW
- id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-deep-research-falcon.md
  title: Deep research report on NaBGL1/BGLU18_6 (Falcon/Edison Scientific Literature)
  findings:
  - statement: No primary publication directly characterizes A0A1J6KFZ7 / BGLU18_6;
      the most defensible annotation rests on GH1 family inference (retaining double-displacement
      mechanism, conserved NEP/TENG catalytic glutamates, (alpha/beta)8 TIM barrel
      fold) plus the nicotine-pathway notes which place this candidate as the
      attenuata ortholog of the experimentally defined beta-GD1/NicGH in the
      A622-MATE1-beta-GD1 cluster.
existing_annotations:
- term:
    id: GO:0004553
    label: hydrolase activity, hydrolyzing O-glycosyl compounds
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: This parent hydrolase term should be collapsed to the more specific beta-glucosidase annotation.
    action: MODIFY
    reason: >-
      GO:0008422 captures the relevant GH1 catalytic specificity more directly.
    proposed_replacement_terms:
    - id: GO:0008422
      label: beta-glucosidase activity
- term:
    id: GO:0005975
    label: carbohydrate metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: This broad process term is too generic to express the pathway-specific conclusion.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The more informative biology is a nicotine-pathway glucoside hydrolase role
      rather than generic carbohydrate metabolism.
- term:
    id: GO:0008422
    label: beta-glucosidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000118
  review:
    summary: This is the core catalytic annotation for the BGLU18_6 candidate.
    action: ACCEPT
    reason: >-
      UniProt and GH1 family assignment support beta-glucosidase chemistry, and
      the pathway paper makes beta-GD1 the late nicotine hydrolase.
    supported_by:
    - reference_id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
      supporting_text: The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.
      reference_section_type: LITERATURE_REVIEW
- term:
    id: GO:0042179
    label: nicotine biosynthetic process
  evidence_type: TAS
  original_reference_id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
  review:
    summary: BGLU18_6 should be added as the leading nicotine-pathway beta-glucosidase candidate.
    action: NEW
    reason: >-
      The paper identifies beta-GD1/NicGH as a core late hydrolase and the
      mapping pass places BGLU18_6 as the best current attenuata ortholog.
    supported_by:
    - reference_id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
      supporting_text: The 2026-04-05 mapping dive assigns NaBGL1 to BGLU18_6 / A0A1J6KFZ7 as the best current sequence-backed NICAT ortholog to tobacco beta-GD1, and explicitly demotes the older BGLU42 launch to a weaker historical comparator.
      reference_section_type: LITERATURE_REVIEW
core_functions:
- molecular_function:
    id: GO:0008422
    label: beta-glucosidase activity
  directly_involved_in:
  - id: GO:0042179
    label: nicotine biosynthetic process
  description: >-
    BGLU18_6 is the best current NICAT candidate for the NicGH/beta-GD1 step
    that hydrolyzes a late nicotine glucoside intermediate.
  supported_by:
  - reference_id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
    supporting_text: The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.
    reference_section_type: LITERATURE_REVIEW
proposed_new_terms:
- proposed_name: nicotine glucoside hydrolase activity
  proposed_definition: >-
    Catalysis of the hydrolysis of a nicotine-pathway glucoside intermediate to
    release nicotine and beta-D-glucose during the late steps of nicotine biosynthesis.
  justification: >-
    The recent nicotine pathway paper resolves a specialized beta-GD1/NicGH
    function that is not captured by the generic beta-glucosidase activity term.
  proposed_parent:
    id: GO:0008422
    label: beta-glucosidase activity
  supported_by:
  - reference_id: file:NICAT/NaBGL1_candidate_BGLU18_6/NaBGL1_candidate_BGLU18_6-notes.md
    supporting_text: The glucosylation preprint makes beta-GD1/NicGH a mechanistically defined late nicotine-pathway hydrolase by placing it in the A622-MATE1-beta-GD1 cluster and using UGT1, A622, BBLa, and beta-GD1 to reconstitute the four-enzyme nicotine synthase cascade.
    reference_section_type: LITERATURE_REVIEW
suggested_questions:
- question: Does A0A1J6KFZ7 account for most NicGH flux in Nicotiana attenuata roots, or is there meaningful redundancy with the beta-GD2-like copy?
- question: What exact glucosylated late intermediate is preferred by the attenuata BGLU18_6 candidate?
suggested_experiments:
- description: Reconstitute BGLU18_6 with the UGT1-A622-BBL module and test hydrolysis of the resulting late nicotine glucosides.
  experiment_type: pathway reconstitution assay
  hypothesis: BGLU18_6 is the principal attenuata NicGH ortholog and efficiently hydrolyzes the pathway nicotine glucoside.
- description: Knock out the BGLU18_6 candidate and measure nicotine glucoside accumulation together with nicotine depletion after induction.
  experiment_type: genetic perturbation plus metabolite profiling
  hypothesis: Loss of BGLU18_6 will cause buildup of late glucosylated intermediates and reduce nicotine output.

NaBGL1_candidate_BGLU18_6

Gene Description

Proposed New Ontology Terms

nicotine glucoside hydrolase activity

Existing Annotations Review

Core Functions

BGLU18_6 is the best current NICAT candidate for the NicGH/beta-GD1 step that hydrolyzes a late nicotine glucoside intermediate.

References

Suggested Questions for Experts

Suggested Experiments

Deep Research

Falcon

Research report: Functional annotation of Nicotiana attenuata BGLU18_6 (UniProt A0A1J6KFZ7)

0) Executive summary and identity verification (critical)

1) Key concepts and definitions (current understanding)

1.1 What “β-glucosidase (GH1)” means

1.2 Catalytic mechanism (retaining double-displacement) and active-site architecture

2) Functional hypotheses for N. attenuata BGLU18_6 (A0A1J6KFZ7)

2.1 Most defensible primary biochemical function (family-level inference)

2.2 Plausible biological roles in plants (general β-glucosidase roles)

3) Recent developments (prioritizing 2023–2024) relevant to functional annotation

3.1 2023: Quantitative evidence that plant β-glucosidases can control active antimicrobial coumarin levels

3.2 2024: Tobacco transcriptomics link glycoside-hydrolase genes to immunity/metabolic reprogramming

4) Structural/biochemical evidence that motivates caution in assigning specific substrates to BGLU18_6

5) Cellular localization: what can be said for BGLU18_6

6) Current applications and real-world implementations (β-glucosidases, including in Nicotiana)

6.1 Plant engineering for biomass saccharification (industrial biotechnology)

6.2 Defense chemistry activation by glucoside hydrolysis (conceptual implementation)

7) Gene symbol ambiguity and “BGLU18” in the literature (why this matters here)

8) Recommended next steps to turn this into a high-confidence functional annotation (evidence-generating)

9) Conclusion

Artifacts

Citations

📚 Additional Documentation

Notes

NaBGL1_candidate_BGLU18_6 Notes

📄 View Raw YAML