A patatin/PNPLA (patatin-like phospholipase domain) family protein from bread wheat (Triticum aestivum), encoded by gene model TraesCS3D02G033600 on chromosome 3D. The protein carries a PNPLA/patatin domain (residues 1-134) belonging to the acyltransferase/lysophospholipase superfamily. Enzymes of this family act as lipid acyl hydrolases, using a non-canonical Ser-Asp catalytic dyad to cleave acyl-ester bonds of glycerolipids (phospholipids, galactolipids and acylglycerols) to release free fatty acids. By sequence it belongs to the plant patatin-related phospholipase A pPLAII subfamily (the soluble lipid-acyl-hydrolase clade, associated with defense and stress responses), so it is predicted to be a non-specific lipolytic acyl hydrolase contributing to lipid metabolism. No function has been experimentally demonstrated for this particular wheat protein, which is an unreviewed (TrEMBL) entry inferred from homology (UniProt PE3). Notably, the currently deposited 302-aa sequence model lacks the N-terminal half of the patatin catalytic domain, including the catalytic-serine nucleophile elbow, so as modeled it would be catalytically inactive - most likely an incomplete gene model, though a degenerate pseudo-enzyme cannot be excluded.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0006629
lipid metabolic process
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: InterPro2GO transfer from the PNPLA/patatin-like phospholipase domain (IPR002641) to the general biological process "lipid metabolic process". This is the exact and sole InterPro2GO mapping for IPR002641, and is biologically appropriate for a patatin-family lipid acyl hydrolase.
Reason: The protein contains a well-defined PNPLA/patatin domain (PROSITE PS51635, residues 1-134; SUPFAM SSF52151; Gene3D 3.40.1090.10), and the patatin family is a family of lipid acyl hydrolases acting on glycerolipids. "Lipid metabolic process" is the correct, appropriately general BP given that only a domain match (not substrate-resolved experimental data) is available. The IEA evidence and InterPro2GO provenance are sound. (Caveat - in-repo bioinformatics shows the deposited model lacks the catalytic serine and may be a truncated gene model; the lipid-metabolic role is therefore a family/subfamily-level inference rather than confirmed for this sequence. Lipid metabolic process is deliberately retained as the substrate- and direction-neutral umbrella and is NOT sharpened to lipid catabolic process, since an acyl hydrolase may act in remodeling or signaling rather than degradation.)
Supporting Evidence:
GO_REF:0000002
GO:0006629 lipid metabolic process; IEA; WITH InterPro:IPR002641 (PNPLA domain)
PMID:12779324
Patatin is a nonspecific lipid acyl hydrolase
file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md
A0A3B6GK97 belongs to the pPLAII subfamily
file:WHEAT/A0A3B6GK97/A0A3B6GK97-deep-research-falcon.md
The best-supported plant functions are lipid mobilization during seed germination, initiation of storage-oil breakdown, membrane phospholipid turnover, and remodeling of LD surfaces to allow access of TAG lipases
|
|
GO:0016787
hydrolase activity
|
IEA
GO_REF:0000117 |
MODIFY |
Summary: ARBA machine-learning electronic annotation assigning the very general molecular function "hydrolase activity". This is correct in essence (patatin/PNPLA proteins are hydrolases) but is uninformatively broad given that the patatin domain reliably confers a specific class of activity, namely carboxylic ester (acyl) hydrolysis of lipids.
Reason: The patatin/PNPLA domain is a lipid acyl hydrolase module that cleaves carboxylic ester bonds of glycerolipids using a Ser-Asp catalytic dyad [PMID:12779324]. "Hydrolase activity" (GO:0016787) is therefore correct but far too general; a more informative and equally well-supported term is "carboxylic ester hydrolase activity" (GO:0052689), the parent of the lipase/phospholipase/acylglycerol-lipase activities characteristic of this family. The UniProt entry's own family-level FUNCTION text describes non-specific lipolytic acyl hydrolase activity hydrolyzing phospholipids and galactolipids. More substrate-specific functions are in fact asserted for this protein by GO_Central as IBA (phylogenetic) annotations - glycerophospholipase activity (GO:0004620) and monoacylglycerol lipase activity (GO:0047372) - which are visible in AmiGO/GOlr but were not returned by the QuickGO GOA pull that seeded this review (see reference GO_REF:0000033 and the AmiGO record at http://amigo.geneontology.org/amigo/gene_product/UniProtKB:A0A3B6GK97). Because those IBA lipase terms already capture the specific activity out of band, this generic ARBA "hydrolase activity" annotation is best modified to their immediate informative parent, "carboxylic ester hydrolase activity" (GO:0052689), rather than left at the root-level hydrolase term or duplicated into the specific IBA terms. IMPORTANT CAVEAT - the family-level MF may not hold for this specific deposited sequence. A reproducible bioinformatics analysis (file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md) shows that the modeled 302-aa protein places in the pPLAII subfamily but LACKS the entire N-terminal half of the patatin catalytic domain - both the oxyanion glycine-rich block (DGGG) and the catalytic-serine nucleophile elbow (G-T-S-T-G) are absent (the sequence has no G-x-S-x-G motif at all), although it retains the catalytic Asp. As modeled it is therefore predicted catalytically INACTIVE (no nucleophile), most likely reflecting an incomplete/incorrect gene model (~100-130 aa shorter than orthologs) rather than - but not excluding - a genuine degenerate pseudo-enzyme. The IBA lipase calls were propagated phylogenetically and do not verify active-site integrity. The MODIFY to carboxylic ester hydrolase activity is retained as the correct FAMILY-level term, but with this explicit caveat that the activity is not verifiable on, and may be absent from, the current sequence model.
Proposed replacements:
carboxylic ester hydrolase activity
Supporting Evidence:
PMID:12779324
Patatin is a nonspecific lipid acyl hydrolase
GO_REF:0000033
Annotation inferences using phylogenetic trees
file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md
the modeled 302-aa protein places in the pPLAII subfamily but LACKS the entire N-terminal half of the patatin catalytic domain - both the oxyanion glycine-rich block (DGGG) and the catalytic-serine nucleophile elbow (G-T-S-T-G) are absent
file:WHEAT/A0A3B6GK97/A0A3B6GK97-deep-research-falcon.md
PNPLA/patatin enzymes use a Ser-Asp catalytic dyad rather than the classical Ser-His-Asp triad of many alpha/beta-hydrolases
|
Q: What is the substrate specificity of this wheat patatin-like protein (phospholipids vs. galactolipids vs. acylglycerols), and which acyl-ester bonds (sn-1/sn-2) does it preferentially hydrolyze?
Q: Is this gene (TraesCS3D02G033600) transcriptionally induced upon pathogen challenge or abiotic stress in wheat, as seen for defense-related patatin-like proteins in other plants?
Q: Is the deposited 302-aa model (which lacks the N-terminal oxyanion DGGG and catalytic-serine G-T-S-T-G motifs) an incomplete/incorrect gene model, or does the locus genuinely encode a catalytically dead pPLAII pseudo-enzyme? (Check the 3A/3B/3D homoeologs, alternative gene models, and RNA-seq evidence for a missing 5' exon.)
Experiment: Express and purify the recombinant protein and assay lipid acyl hydrolase activity against defined substrates (phospholipids, galactolipids, mono/di-acylglycerols), with catalytic-Ser mutagenesis to confirm the predicted Ser-Asp dyad.
Type: in vitro enzyme assay
Experiment: Profile expression of TraesCS3D02G033600 across tissues and in response to fungal/bacterial pathogen infection to test a possible defense role.
Type: transcriptomics
Experiment: Verify/curate the gene model - inspect the genomic locus, splice junctions and RNA-seq coverage at the 5' end and compare with the 3A/3B/3D homoeologs to determine whether the missing N-terminal catalytic exon (oxyanion + catalytic Ser) reflects a gene annotation error or a true loss of the catalytic serine.
Type: gene model curation / comparative genomics
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.
Direct literature on the wheat protein A0A3B6GK97 is not available in the current scientific literature. A0A3B6GK97 is a UniProt accession identifier for a PNPLA domain-containing protein from Triticum aestivum (wheat) belonging to the patatin family. Since no specific studies have characterized this particular protein, the functional annotation presented here is based on extensive research of the PNPLA/patatin protein family in plants, particularly from closely related cereal species (rice, pearl millet) and oilseed crops, combined with structural and domain information from the UniProt annotation.
A0A3B6GK97 is annotated as a PNPLA domain-containing protein belonging to the patatin family (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4). The protein contains two key domains: the Acyl_Trfase/lysoPLipase domain (IPR016035) and the PNPLA_dom (IPR002641), which are characteristic of patatin-like phospholipase family members (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 1-2).
The patatin family of proteins is named after patatin, a major storage protein first identified in potato tubers that exhibits lipid acyl hydrolase activity (wu2025themultifunctionalrole pages 1-2). In the broader classification system, PNPLA proteins are characterized by the presence of a conserved patatin-like phospholipase domain (PROSITE entry PS51635) featuring an α/β fold structure (dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 1-2).
PNPLA domain-containing proteins, including the wheat A0A3B6GK97, employ a distinctive catalytic mechanism that differs from classical lipases. The active site contains a Ser-Asp catalytic dyad rather than the more common Ser-His-Asp catalytic triad found in many α/β-hydrolase enzymes (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4). The catalytic serine is situated within the classical lipase motif GxSxG (where x represents any amino acid), while the aspartic acid resides in the DGA/G motif (lulic2023thepnplafamily pages 1-2, lulic2023thepnplafamily pages 2-4).
The catalytic mechanism proceeds through a nucleophilic attack: the catalytic serine's hydroxyl group attacks the carbonyl carbon of the substrate's ester bond, forming a covalent acyl-enzyme intermediate (dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4). The aspartic acid functions as both a general acid and general base, facilitating substrate binding and subsequent regeneration of the active enzyme (lulic2023thepnplafamily pages 2-4). An oxyanion hole, positioned near the catalytic dyad and characterized by a glycine-rich region, stabilizes the transition state during the hydrolysis reaction (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4).
This structural organization places the patatin-like domain at the core of the enzyme's catalytic function, with the α/β fold creating a central β-sheet sandwiched between α-helices (lulic2023thepnplafamily pages 1-2).
PNPLA family proteins in plants exhibit multiple enzymatic activities, functioning primarily as calcium-independent phospholipases (Ca²⁺-independent phospholipases A2, or iPLA2s), meaning they do not require calcium for activity or translocation (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 1-2). This distinguishes them from classical phospholipase A2 enzymes.
Primary enzymatic activities include:
Phospholipase A Activity: The primary function involves hydrolyzing fatty acids from the sn-1 and/or sn-2 positions of glycerophospholipids (lulic2023thepnplafamily pages 1-2, yaginuma2022currentknowledgeon pages 1-3). Studies in rice have demonstrated that related phospholipase proteins can act on phosphatidylcholine (PC), the major phospholipid component of lipid droplet membranes (dolui2020osplbgeneexpressed pages 1-2, qin2023molecularmachineryof pages 4-6).
Lipase Activity: Beyond phospholipids, plant PNPLA proteins can hydrolyze neutral lipids, particularly triacylglycerols (TAGs), which are the primary storage lipids in seeds (lulic2023thepnplafamily pages 1-2, wang2021genomewideassociationstudy pages 1-2).
Transacylase Activity: Some family members exhibit acyltransferase activity, catalyzing the transfer of acyl groups between lipid molecules (lulic2023thepnplafamily pages 1-2, schratter2022abhd5—aregulatorof pages 1-2).
Substrate specificity: Research on plant PNPLA/patatin proteins reveals preferred substrates including:
- Phosphatidylcholine (PC), especially species containing C28, C32, and C34 acyl chains with unsaturated fatty acids (dolui2020osplbgeneexpressed pages 1-2, qin2023molecularmachineryof pages 4-6)
- Phosphatidylserine (PS) and phosphatidic acid (PA) in some family members (yaginuma2022currentknowledgeon pages 1-3)
- Triacylglycerols and diacylglycerols (wang2021genomewideassociationstudy pages 1-2)
- Lysophospholipids, with some enzymes exhibiting lysophospholipase activity (lulic2023thepnplafamily pages 1-2)
A key finding from cereal research is that a rice germination-associated phospholipase B (OsPLB) showed specificity for PC species with unsaturated fatty acids, hydrolyzing both sn-1 and sn-2 positions to release free fatty acids and lysophospholipids (dolui2020osplbgeneexpressed pages 1-2). This activity pattern is likely representative of the wheat A0A3B6GK97 protein given the conservation of PNPLA function across cereals.
Plant PNPLA/patatin family proteins function in intracellular compartments, with no evidence for secretion or extracellular activity. The primary localization sites include:
1. Cytosol: Many PNPLA proteins exist as soluble enzymes in the cytoplasm prior to recruitment to their sites of action (lulic2023thepnplafamily pages 2-4, qin2023molecularmachineryof pages 4-6).
2. Lipid Droplets (LDs): The most functionally significant localization is at lipid droplets, the cellular organelles that store neutral lipids such as TAGs (qin2023molecularmachineryof pages 4-6, qin2023molecularmachineryof pages 1-2). Plant phospholipases containing patatin-like domains associate with the LD surface through hydrophobic domains, positioning them to access the phospholipid monolayer that surrounds the TAG core (qin2023molecularmachineryof pages 4-6). Studies in cucumber and sunflower seeds have demonstrated that patatin-like PLA2 enzymes are exclusively confined to lipid droplets during seed germination (qin2023molecularmachineryof pages 4-6).
3. ER-Associated: Some evidence suggests association with the endoplasmic reticulum during lipid droplet biogenesis (qin2023molecularmachineryof pages 1-2).
4. Vacuolar/Tonoplast Association: During lipophagy (autophagy-mediated lipid droplet degradation), some phospholipases may associate with the vacuolar membrane (tonoplast) (qin2023molecularmachineryof pages 4-6, qin2023molecularmachineryof pages 1-2).
The dynamic localization pattern is particularly evident during seed germination, when phospholipase activity migrates from the cytosol to the lipid droplet surface, coinciding with the phase of maximal lipolysis (qin2023molecularmachineryof pages 4-6). This recruitment mechanism allows the enzyme to access its substrates—the phospholipids and TAGs that must be mobilized to provide energy for seedling growth.
The wheat PNPLA protein A0A3B6GK97 likely participates in several interconnected lipid metabolism pathways:
1. Lipid Mobilization During Seed Germination
The most well-characterized function of plant PNPLA/patatin proteins is in storage lipid mobilization during seed germination (dolui2020functionalomicsidentifies pages 1-4, dolui2020osplbgeneexpressed pages 1-2, qin2023molecularmachineryof pages 1-2). In germinating cereal seeds, stored lipids must be broken down to provide energy and carbon equivalents for seedling establishment before photosynthesis begins.
The process occurs in stages:
- Phospholipase activity at lipid droplets hydrolyzes the phospholipid monolayer (primarily PC) that encases the TAG core, creating "holes" approximately 80 nm wide in the membrane (qin2023molecularmachineryof pages 4-6)
- These openings allow larger enzymes, including TAG lipases such as SUGAR-DEPENDENT1 (SDP1) in Arabidopsis, to access and hydrolyze the triacylglycerol matrix (qin2023molecularmachineryof pages 1-2)
- The released free fatty acids are converted to acyl-CoA and enter peroxisomes (glyoxysomes in germinating seeds) for β-oxidation (qin2023molecularmachineryof pages 1-2)
- Acetyl-CoA from β-oxidation enters the glyoxylate cycle, producing succinate that is converted to malate
- Malate feeds into gluconeogenesis, generating soluble sugars that fuel seedling growth (qin2023molecularmachineryof pages 1-2)
Studies in rice have shown that phospholipase activity increases rapidly during germination, with maximum expression coinciding with peak lipid mobilization (dolui2020functionalomicsidentifies pages 1-4, dolui2020osplbgeneexpressed pages 1-2). The coordinated action of phospholipases and TAG lipases is essential for efficient energy mobilization.
2. Membrane Lipid Remodeling
Beyond storage lipid mobilization, PNPLA proteins participate in ongoing membrane lipid remodeling, which is crucial for maintaining membrane homeostasis and adapting to changing cellular conditions (qin2023molecularmachineryof pages 4-6). The conversion of PC to lysophosphatidylcholine (lyso-PC) through phospholipase A activity represents a key step in membrane lipid turnover (qin2023molecularmachineryof pages 4-6). This remodeling process affects membrane fluidity, permeability, and the proper functioning of membrane-embedded proteins.
3. Stress Response Pathways
Plant membrane lipid metabolism undergoes substantial reorganization during abiotic stress conditions such as drought, salinity, and temperature extremes. PNPLA family members contribute to stress adaptation through several mechanisms (wu2025themultifunctionalrole pages 1-2):
- Altering membrane lipid composition to maintain membrane integrity under stress
- Generating signaling lipids that activate stress response pathways
- Reallocating resources from growth to defense when needed
In potato tubers, patatin protein levels, stability, and enzymatic activity shift under drought, salinity, and pathogen stress, affecting both lipid metabolism and defense responses (wu2025themultifunctionalrole pages 1-2).
4. Phosphate Starvation Response
Under phosphate-limited conditions, plants mobilize phosphorus from membrane phospholipids to maintain cellular phosphate homeostasis. Phospholipases, including PNPLA family members, hydrolyze phospholipids to release inorganic phosphate (Pi), with the resulting membrane remodeling also involving increased synthesis of galactolipids that can substitute for phospholipids in membranes (qin2023molecularmachineryof pages 4-6).
5. Lipophagy
Lipid droplets can also be degraded through autophagy (lipophagy), where LDs are delivered to vacuoles for breakdown. Evidence suggests that lipases with vacuolar localization, potentially including some PNPLA family members, may participate in degrading autophagic bodies containing lipid material (qin2023molecularmachineryof pages 1-2).
While direct studies on A0A3B6GK97 are unavailable, the collective evidence from plant PNPLA research allows inference of likely physiological roles in wheat:
1. Seed Germination and Seedling Establishment: The protein likely plays a critical role in wheat grain germination by initiating the breakdown of stored lipids, providing energy and carbon skeletons for the developing seedling until photosynthesis is established (dolui2020functionalomicsidentifies pages 1-4, dolui2020osplbgeneexpressed pages 1-2).
2. Grain Quality and Oil Content: Studies in rapeseed (Brassica napus) have demonstrated that genetic variation in patatin-like lipase genes significantly affects seed oil content, with certain alleles associated with a 4.7–6.2% reduction in oil accumulation (wang2021genomewideassociationstudy pages 1-2). This suggests that wheat homologs like A0A3B6GK97 may influence grain lipid content and potentially nutritional quality.
3. Stress Adaptation: Given the documented roles of PNPLA proteins in stress responses across plant species, the wheat protein likely contributes to adaptation under environmental stresses relevant to wheat cultivation, including drought, heat, and salinity stress (wu2025themultifunctionalrole pages 1-2).
4. Membrane Homeostasis: The enzyme probably maintains cellular membrane integrity and function through continuous lipid turnover and remodeling, which is essential for all cellular processes (qin2023molecularmachineryof pages 4-6).
While direct expression data for A0A3B6GK97 are not available, studies of analogous proteins in related species provide insights into likely expression patterns:
By inference, wheat A0A3B6GK97 is likely expressed during grain development and germination, with potential upregulation under stress conditions requiring membrane remodeling or mobilization of lipid reserves.
The PNPLA/patatin family represents an evolutionarily conserved system for intracellular lipid metabolism. The family's expansion in plants reflects the critical importance of precise lipid regulation for seed-based reproduction strategies. The dual capacity to act on both phospholipids and neutral lipids positions these enzymes as key integrators of storage lipid catabolism and membrane dynamics.
Recent advances (2023-2025) have refined our understanding of plant lipid droplet biology, revealing the sophisticated coordination between lipolysis (enzyme-catalyzed degradation on LD surfaces) and lipophagy (autophagy-mediated degradation) pathways (qin2023molecularmachineryof pages 1-2). PNPLA proteins participate primarily in the lipolytic pathway, though connections to lipophagy mechanisms are emerging.
| Protein Feature/Characteristic | Description | Citations |
|---|---|---|
| Protein family/domain structure | A0A3B6GK97 is annotated in UniProt as a wheat PNPLA domain-containing protein belonging to the patatin family. Plant and other PNPLA proteins share a conserved patatin-like phospholipase domain (PROSITE PS51635) with an α/β fold, a glycine-rich oxyanion-hole region, a lipase consensus motif GxSxG containing the catalytic serine, and a conserved DGA/G-type motif containing the catalytic aspartate. | (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 1-2) |
| Catalytic mechanism | PNPLA/patatin enzymes use a Ser-Asp catalytic dyad rather than the classical Ser-His-Asp triad of many α/β-hydrolases. The catalytic serine attacks the ester bond of the lipid substrate, forms an acyl-enzyme intermediate, and the oxyanion hole stabilizes the transition state before hydrolysis releases free fatty acid and regenerates the enzyme. | (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4) |
| Enzymatic activities | Across plants and other eukaryotes, PNPLA/patatin proteins are described as Ca2+-independent phospholipases with lipase/phospholipase A-type activities; some family members also show lysophospholipase or transacylase activity. In plant systems, patatin proteins and related phospholipases participate in phospholipid hydrolysis on lipid-droplet surfaces and in membrane remodeling. | (lulic2023thepnplafamily pages 1-2, dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 1-2, qin2023molecularmachineryof pages 4-6, wu2025themultifunctionalrole pages 1-2) |
| Substrate specificity | Family-level evidence indicates activity toward phospholipids and neutral lipids. A rice germination phospholipase B (OsPLB) hydrolyzed phosphatidylcholine (PC), especially PC species with C28, C32, and C34 unsaturated acyl chains. Plant lipid-droplet phospholipase activity has been linked to hydrolysis of the phospholipid monolayer, particularly PC, while broader patatin-like enzymes in plants and related systems can act on phospholipids, lysophospholipids, and triacylglycerols. | (dolui2020osplbgeneexpressed pages 1-2, qin2023molecularmachineryof pages 4-6, wang2021genomewideassociationstudy pages 1-2) |
| Cellular localization | Plant PNPLA/patatin-related lipid hydrolases are predominantly intracellular. Evidence from germinating seeds places relevant phospholipase activity on lipid droplets (LDs), where enzymes act on the LD phospholipid monolayer; some are detected in cytosol before recruitment to LDs. Broader PNPLA literature also supports soluble cytosolic and LD-associated states for patatin-domain proteins. | (lulic2023thepnplafamily pages 2-4, qin2023molecularmachineryof pages 4-6, qin2023molecularmachineryof pages 1-2) |
| Biological processes | The best-supported plant functions are lipid mobilization during seed germination, initiation of storage-oil breakdown, membrane phospholipid turnover, and remodeling of LD surfaces to allow access of TAG lipases. These proteins also contribute to broader membrane homeostasis and adaptation processes. | (dolui2020functionalomicsidentifies pages 1-4, dolui2020osplbgeneexpressed pages 1-2, qin2023molecularmachineryof pages 4-6, qin2023molecularmachineryof pages 1-2) |
| Biochemical pathways | PNPLA/patatin proteins function in storage-lipid mobilization pathways: phospholipid monolayer hydrolysis at LDs facilitates TAG breakdown; released fatty acids are converted to acyl-CoA, enter peroxisomal β-oxidation, then the glyoxylate cycle and gluconeogenesis to support seedling establishment. They also participate in membrane-lipid remodeling pathways involving PC and lysophospholipid turnover. | (dolui2020osplbgeneexpressed pages 1-2, qin2023molecularmachineryof pages 1-2) |
| Expression patterns (when/where expressed) | Direct expression data for A0A3B6GK97 are unavailable, but analogous plant PNPLA/patatin proteins are enriched when lipid mobilization is needed. In rice, germination-associated phospholipases are induced during seed germination; in Brassica napus, patatin-like lipase family members are preferentially expressed in reproductive tissues, especially maturing seeds. This supports a likely role for wheat homologs in seed/grain lipid metabolism or stress-linked membrane remodeling. | (dolui2020functionalomicsidentifies pages 1-4, dolui2020osplbgeneexpressed pages 1-2, wang2021genomewideassociationstudy pages 1-2) |
| Physiological roles | Inference from plant family studies suggests that wheat A0A3B6GK97 most likely contributes to intracellular lipid metabolism rather than extracellular signaling. Likely roles include facilitating seed reserve mobilization, regulating membrane composition, supporting stress adaptation, and modulating seed oil/grain lipid traits. In rapeseed, natural variation in a patatin-like lipase was associated with a 4.7–6.2% reduction in seed oil content, supporting physiologic relevance of this family to seed lipid balance. | (wang2021genomewideassociationstudy pages 1-2, wu2025themultifunctionalrole pages 1-2) |
Table: This table summarizes the main structural, enzymatic, cellular, and physiological features of plant PNPLA/patatin family proteins that are most relevant for inferring the function of the wheat protein A0A3B6GK97. It is useful because direct literature on A0A3B6GK97 is limited, so family-level evidence provides the strongest annotation basis.
The functional characterization of A0A3B6GK97 presented here is based entirely on inference from family-level studies, structural domain predictions, and research on orthologous proteins in other plant species. Direct experimental characterization of this specific wheat protein would be necessary to:
- Confirm its precise substrate specificity
- Determine its exact cellular localization in wheat tissues
- Define its expression pattern across development and stress conditions
- Establish its specific role in wheat grain quality or stress tolerance
- Identify regulatory mechanisms controlling its activity
The wheat protein A0A3B6GK97, classified as a PNPLA domain-containing protein of the patatin family, likely functions as a calcium-independent phospholipase with broad substrate specificity for phospholipids and triacylglycerols. Based on conserved family characteristics, the enzyme probably localizes to the cytosol and lipid droplet surfaces, where it catalyzes the hydrolysis of ester bonds using a Ser-Asp catalytic dyad mechanism. Its primary physiological roles likely include facilitating lipid mobilization during grain germination, maintaining membrane homeostasis, and contributing to stress adaptation responses. The enzyme operates within interconnected pathways of lipid catabolism, ultimately supporting energy production and carbon allocation for seedling growth. Further experimental characterization of this specific wheat protein would provide valuable insights for improving wheat grain quality, germination efficiency, and stress resilience in breeding programs.
References
(lulic2023thepnplafamily pages 1-2): Ana-Marija Lulić and Maja Katalinić. The pnpla family of enzymes: characterisation and biological role. Archives of Industrial Hygiene and Toxicology, 74:75-89, Jun 2023. URL: https://doi.org/10.2478/aiht-2023-74-3723, doi:10.2478/aiht-2023-74-3723. This article has 26 citations.
(dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 2-4): Noopur Dubey, Lina Riegler‐Berket, and Monika Oberer. Patatin‐domain‐containing (phospho)lipases under control: mammalian co‐regulators and pathogenic activation mechanisms. FEBS Open Bio, 16:279-298, Jan 2026. URL: https://doi.org/10.1002/2211-5463.70201, doi:10.1002/2211-5463.70201. This article has 1 citations and is from a peer-reviewed journal.
(dubey2026patatin‐domain‐containing(phospho)lipasesunder pages 1-2): Noopur Dubey, Lina Riegler‐Berket, and Monika Oberer. Patatin‐domain‐containing (phospho)lipases under control: mammalian co‐regulators and pathogenic activation mechanisms. FEBS Open Bio, 16:279-298, Jan 2026. URL: https://doi.org/10.1002/2211-5463.70201, doi:10.1002/2211-5463.70201. This article has 1 citations and is from a peer-reviewed journal.
(wu2025themultifunctionalrole pages 1-2): Yicong Wu, Yunxia Zeng, Wenying Zhang, and Yonghong Zhou. The multifunctional role of patatin in potato tuber sink strength, starch biosynthesis, and stress adaptation: a systematic review. Biology, 15:29, Dec 2025. URL: https://doi.org/10.3390/biology15010029, doi:10.3390/biology15010029. This article has 1 citations.
(lulic2023thepnplafamily pages 2-4): Ana-Marija Lulić and Maja Katalinić. The pnpla family of enzymes: characterisation and biological role. Archives of Industrial Hygiene and Toxicology, 74:75-89, Jun 2023. URL: https://doi.org/10.2478/aiht-2023-74-3723, doi:10.2478/aiht-2023-74-3723. This article has 26 citations.
(yaginuma2022currentknowledgeon pages 1-3): Shun Yaginuma, Hiroki Kawana, and Junken Aoki. Current knowledge on mammalian phospholipase a1, brief history, structures, biochemical and pathophysiological roles. Molecules, 27:2487, Apr 2022. URL: https://doi.org/10.3390/molecules27082487, doi:10.3390/molecules27082487. This article has 34 citations.
(dolui2020osplbgeneexpressed pages 1-2): Achintya Kumar Dolui, Mahadev Latha, and Panneerselvam Vijayaraj. Osplb gene expressed during seed germination encodes a phospholipase in rice. 3 Biotech, 10:1-9, Jan 2020. URL: https://doi.org/10.1007/s13205-019-2016-x, doi:10.1007/s13205-019-2016-x. This article has 12 citations and is from a peer-reviewed journal.
(qin2023molecularmachineryof pages 4-6): Zhaoxia Qin, Tianyu Wang, Yanxiu Zhao, Changle Ma, and Qun Shao. Molecular machinery of lipid droplet degradation and turnover in plants. International Journal of Molecular Sciences, 24:16039, Nov 2023. URL: https://doi.org/10.3390/ijms242216039, doi:10.3390/ijms242216039. This article has 18 citations.
(wang2021genomewideassociationstudy pages 1-2): Haoyi Wang, Qian Wang, Haksong Pak, Tao Yan, Mingxun Chen, Xiaoyang Chen, Dezhi Wu, and Lixi Jiang. Genome-wide association study reveals a patatin-like lipase relating to the reduction of seed oil content in brassica napus. BMC Plant Biology, Jan 2021. URL: https://doi.org/10.1186/s12870-020-02774-w, doi:10.1186/s12870-020-02774-w. This article has 29 citations and is from a peer-reviewed journal.
(schratter2022abhd5—aregulatorof pages 1-2): Margarita Schratter, Achim Lass, and Franz P. W. Radner. Abhd5—a regulator of lipid metabolism essential for diverse cellular functions. Metabolites, 12:1015, Oct 2022. URL: https://doi.org/10.3390/metabo12111015, doi:10.3390/metabo12111015. This article has 25 citations.
(qin2023molecularmachineryof pages 1-2): Zhaoxia Qin, Tianyu Wang, Yanxiu Zhao, Changle Ma, and Qun Shao. Molecular machinery of lipid droplet degradation and turnover in plants. International Journal of Molecular Sciences, 24:16039, Nov 2023. URL: https://doi.org/10.3390/ijms242216039, doi:10.3390/ijms242216039. This article has 18 citations.
(dolui2020functionalomicsidentifies pages 1-4): Achintya Kumar Dolui and Panneerselvam Vijayaraj. Functional omics identifies serine hydrolases that mobilize storage lipids during rice seed germination1. Plant Physiology, 184:693-708, Aug 2020. URL: https://doi.org/10.1104/pp.20.00268, doi:10.1104/pp.20.00268. This article has 27 citations and is from a highest quality peer-reviewed journal.
Deep-research providers (falcon, perplexity) were not available in this environment
(no API keys; the falcon attempt failed with a template/credentials error). Per project
guidance, the manual research below is recorded in this notes file rather than a
-deep-research-{provider}.mdfile. No PMIDs are cited in the GOA (annotations are all
homology-based IEA), sofetch-gene-pmidsreturned nothing to cache.
TraesCS3D02G033600 (chromosome 3D, IWGSCThe UniProt flat file lists two IBA molecular-function terms that are absent from the
QuickGO -goa.tsv pull used to seed the review (which returned only the 2 IEAs above).
I verified these directly against AmiGO/GOlr (via the GO MCP search_annotations on
UniProtKB:A0A3B6GK97; web record:
http://amigo.geneontology.org/amigo/gene_product/UniProtKB:A0A3B6GK97):
| GO term | Label | Evidence | Reference | Assigned by | Date |
|---|---|---|---|---|---|
| GO:0004620 | glycerophospholipase activity | IBA (ECO:0000318) | GO_REF:0000033 | GO_Central | 2017-02-28 |
| GO:0047372 | monoacylglycerol lipase activity | IBA (ECO:0000318) | GO_REF:0000033 | GO_Central | 2017-02-28 |
QuickGO and AmiGO are complementary here: QuickGO returned only the 2 IEAs
(InterPro2GO + ARBA); AmiGO/GOlr returned only the 2 GO_Central IBAs. These IBA
annotations are manually-reviewed phylogenetic (PAINT) assertions that this protein is a
lipase (glycerophospholipase + monoacylglycerol lipase), which is stronger and more
specific than the generic IEA hydrolase term.
Handling decision (per maintainer): do NOT add these IBAs to existing_annotations —
the CI consistency check requires existing_annotations to mirror the seeded GOA tsv, so
adding rows it doesn't contain would fail CI. Instead they are recorded as out-of-band
knowledge: cited via GO_REF:0000033 (with the AmiGO URL) in the references list and
woven into the GO:0016787 MODIFY reasoning and core_functions. They reinforce (but do
not change) the MODIFY of the generic hydrolase IEA toward carboxylic ester hydrolase
activity, the immediate informative parent of both IBA lipase terms.
The UniProt flat file additionally lists GO:0006952 defense response (IEA:UniProtKB-KW),
also not in the GOA pull; defense response for this specific locus is unsupported beyond
keyword propagation and is not asserted here.
Reproducible analysis in A0A3B6GK97-bioinformatics/ (see RESULTS.md). MSA of the query
against 13 characterized plant pPLAs (Arabidopsis pPLAI/II/III, rice PLP1/2, potato patatin)
with FAMSA + BioPython; input-driven control included.
Two findings:
1. Subfamily = pPLAII. The query is 42–50% identical to the pPLAII subfamily and rice
pPLAs, vs only ~23% to pPLAIII and ~16% to pPLAI; NJ tree places it in the pPLAII/rice/
patatin clade. So it is the soluble acyl-hydrolase (defense/wounding/stress) clade, NOT
the pPLAIII galactolipase/growth clade or the large iPLA2-like pPLAI. Single-domain
architecture + this placement make a membrane-trafficking role very unlikely (answers
the trafficking question raised in review).
2. The deposited 302-aa model lacks the catalytic serine. It is fully gapped through the
N-terminal patatin catalytic core: no oxyanion DGGG block and no catalytic-Ser
G-T-S-T-G nucleophile elbow (zero G-x-S-x-G motifs in 302 aa); it retains only the
C-terminal portion incl. the catalytic Asp (D121). Every active reference has GTSTG+DGGG;
the annotated-inactive PLP9 control also lacks GTSTG. Predicted catalytically inactive
as modeled. Most parsimonious = incomplete/incorrect gene model (~100–130 aa shorter
than orthologs, missing a clean N-terminal block), though a true degenerate pseudo-enzyme
cannot be excluded from sequence alone (would need genomic/homoeolog/RNA-seq checks).
Consequence: the GO_Central IBA lipase calls (GO:0004620, GO:0047372) were propagated
phylogenetically and do NOT verify active-site integrity, so they are not supported by the
current sequence. The review keeps the MODIFY → carboxylic ester hydrolase activity as the
family-level term but adds this explicit caveat, and flags the gene model for curation.
A plausibly-real but entirely uncharacterized wheat patatin/PNPLA-family lipid acyl
hydrolase. All evidence is homology/profile-based (IEA). No experimental data, no
gene-specific publications. Reviews should stay conservative: the two IEA annotations are
biologically reasonable; the MF (hydrolase activity) is under-specific and is the main
candidate for refinement.
Question. (1) Which plant patatin-related phospholipase A (pPLA) subfamily does
this protein belong to (to refine the functional inference beyond the domain-level
"lipid metabolic process"), and (2) is its catalytic machinery intact (i.e., is it a
genuine acyl hydrolase, a pseudoenzyme, or a truncated model)?
TL;DR.
- By sequence identity and tree placement over the region it retains, A0A3B6GK97 belongs
to the pPLAII subfamily (42–50% identity to pPLAII / rice pPLAs; ~23% to pPLAIII;
~16% to pPLAI). It is not a pPLAIII (galactolipase/growth) or pPLAI (iPLA2-like) protein.
- However, the modeled 302-aa sequence lacks the entire N-terminal half of the patatin
catalytic domain — both the oxyanion glycine-rich block (DGGG) and the catalytic
serine nucleophile elbow (G-T-S-T-G) are absent. It retains the C-terminal portion
including the catalytic Asp. As deposited, the protein is therefore predicted to be
catalytically inactive (no nucleophilic serine).
- Most parsimonious explanation: an incomplete/incorrect gene model (TraesCS3D02G033600
is ~100–130 aa shorter than full-length orthologs, missing exactly the N-terminal catalytic
exon region). A genuine degenerate pseudo-enzyme cannot be excluded from sequence alone.
This is a caveat to the lipase interpretation: the GO_Central IBA annotations
(glycerophospholipase GO:0004620, monoacylglycerol lipase GO:0047372) are phylogenetic
propagations that assume an intact active site and do not verify it; the modeled
sequence cannot support those activities as-is.
All sequences fetched live from the UniProt REST API; no sequences or results are
hardcoded. Reproduce with just all (recipes: fetch, analyze, test-control).
data/reference_accessions.tsv.G-x-S-x-G andDGGG; (b) MSA column conservation among the core active single-domain enzymesresults/alignment.fasta, pairwise_identity_to_query.tsv, nj_tree.newick,motif_scan.tsv, catalytic_site.tsv, catalytic_columns_all_seqs.tsv, summary.json.results/pairwise_identity_to_query.tsv (%identity to query, over ~98% query coverage):
| Reference | Subfamily | %id |
|---|---|---|
| At pPLAIIα PLP2 (O48723) | pPLAII | 50.5 |
| Rice PLP1 (Q84QY3) | pPLA (rice) | 50.0 |
| Rice PLP2 (Q6ZJD3) | pPLA (rice) | 46.8 |
| At pPLAIIβ PLP3 (O23181) | pPLAII | 46.0 |
| At pPLAIIδ PLP5 (O23180) | pPLAII | 45.6 |
| At pPLAIIε PLP4 (Q9FIY1) | pPLAII | 43.5 |
| At pPLAIIγ PLP1 (O23179) | pPLAII | 42.6 |
| Potato patatin (P15478) | storage | 36.9 |
| At pPLAIIIδ PLP9 (Q93ZQ3) | pPLAIII (inactive) | 23.9 |
| At pPLAIIIα/β/γ | pPLAIII | 22.4–23.7 |
| At pPLAI PLA1 (F4HX15) | pPLAI | 15.8 |
The whole pPLAII subfamily (+ rice pPLAs) ranks at 42–50%, with a clear gap to pPLAIII
(~23%) and pPLAI (16%). The NJ tree (nj_tree.newick) places the query within the
pPLAII/rice/patatin clade, separate from pPLAIII and the long-branch pPLAI. Nearest
neighbours by patristic distance: rice PLP2, At pPLAIIα, At pPLAIIγ, At pPLAIIδ.
Conclusion: pPLAII-type (the "classic" lipid acyl hydrolase clade — defense/wounding/
stress-associated in Arabidopsis), over the portion of the domain the model retains.
MSA-independent motif scan (results/motif_scan.tsv):
| Sequence | len | G-x-S-x-G (catalytic Ser) | DGGG (oxyanion) |
|---|---|---|---|
| QUERY A0A3B6GK97 | 302 | 0 — NONE | 0 — NONE |
| At pPLAIIα PLP2 | 407 | 1 — pos 66 (GTSTG) | pos 25 |
| At pPLAIIβ/γ/δ/ε | 401–428 | 1 — GTSTG | present |
| Rice PLP1 / PLP2 | 405–432 | 1 — GTSTG | present |
| Potato patatin P15478 | 386 | 1 — pos 77 (GTSTG) | pos 35 |
| At pPLAIIIδ PLP9 (inactive ctrl) | 384 | 0 — NONE | present |
Every active reference carries the canonical G-T-S-T-G nucleophile elbow; the query has
no G-x-S-x-G anywhere in 302 aa and no DGGG oxyanion block. The MSA
(results/catalytic_columns_all_seqs.tsv, and the alignment around cols 540–600) shows the
query fully gapped through the N-terminal catalytic core — its modeled N-terminus begins
downstream of where the catalytic Ser sits. The query does retain the catalytic-Asp
region (Asp121, in NLIDSG), matching the active references.
Interpretation: the model has the C-terminal ~⅔ of the patatin domain (incl. catalytic Asp)
but is missing the N-terminal ~⅓ bearing the oxyanion and the catalytic serine. Without the
nucleophilic Ser, acyl-ester hydrolysis is mechanistically impossible — predicted inactive
as modeled.
Re-running with potato patatin relabelled as the query (just test-control,
results_control/) correctly recovers intact motifs (GTSTG pos 77, DGGG pos 35) and a
pPLAII/patatin placement — confirming the query's "motifs absent" result is a property of the
A0A3B6GK97 sequence, not an artifact.
test-control) with active patatin asjust all).results/ and results_control/.data/reference_accessions.tsv.id: A0A3B6GK97
gene_symbol: A0A3B6GK97
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:4565
label: Triticum aestivum
description: A patatin/PNPLA (patatin-like phospholipase domain) family protein from
bread wheat (Triticum aestivum), encoded by gene model TraesCS3D02G033600 on chromosome
3D. The protein carries a PNPLA/patatin domain (residues 1-134) belonging to the
acyltransferase/lysophospholipase superfamily. Enzymes of this family act as lipid
acyl hydrolases, using a non-canonical Ser-Asp catalytic dyad to cleave acyl-ester
bonds of glycerolipids (phospholipids, galactolipids and acylglycerols) to release
free fatty acids. By sequence it belongs to the plant patatin-related phospholipase A
pPLAII subfamily (the soluble lipid-acyl-hydrolase clade, associated with defense and
stress responses), so it is predicted to be a non-specific lipolytic acyl hydrolase
contributing to lipid metabolism. No function has been experimentally demonstrated for
this particular wheat protein, which is an unreviewed (TrEMBL) entry inferred from
homology (UniProt PE3). Notably, the currently deposited 302-aa sequence model lacks the
N-terminal half of the patatin catalytic domain, including the catalytic-serine
nucleophile elbow, so as modeled it would be catalytically inactive - most likely an
incomplete gene model, though a degenerate pseudo-enzyme cannot be excluded.
existing_annotations:
- term:
id: GO:0006629
label: lipid metabolic process
evidence_type: IEA
original_reference_id: GO_REF:0000002
qualifier: involved_in
review:
summary: InterPro2GO transfer from the PNPLA/patatin-like phospholipase domain
(IPR002641) to the general biological process "lipid metabolic process". This
is the exact and sole InterPro2GO mapping for IPR002641, and is biologically
appropriate for a patatin-family lipid acyl hydrolase.
action: ACCEPT
reason: The protein contains a well-defined PNPLA/patatin domain (PROSITE PS51635,
residues 1-134; SUPFAM SSF52151; Gene3D 3.40.1090.10), and the patatin family
is a family of lipid acyl hydrolases acting on glycerolipids. "Lipid metabolic
process" is the correct, appropriately general BP given that only a domain match
(not substrate-resolved experimental data) is available. The IEA evidence and
InterPro2GO provenance are sound. (Caveat - in-repo bioinformatics shows the deposited
model lacks the catalytic serine and may be a truncated gene model; the lipid-metabolic
role is therefore a family/subfamily-level inference rather than confirmed for this
sequence. Lipid metabolic process is deliberately retained as the substrate- and
direction-neutral umbrella and is NOT sharpened to lipid catabolic process, since an
acyl hydrolase may act in remodeling or signaling rather than degradation.)
supported_by:
- reference_id: GO_REF:0000002
supporting_text: GO:0006629 lipid metabolic process; IEA; WITH InterPro:IPR002641
(PNPLA domain)
- reference_id: PMID:12779324
supporting_text: Patatin is a nonspecific lipid acyl hydrolase
- reference_id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md
supporting_text: A0A3B6GK97 belongs to the pPLAII subfamily
- reference_id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-deep-research-falcon.md
supporting_text: The best-supported plant functions are lipid mobilization during
seed germination, initiation of storage-oil breakdown, membrane phospholipid
turnover, and remodeling of LD surfaces to allow access of TAG lipases
- term:
id: GO:0016787
label: hydrolase activity
evidence_type: IEA
original_reference_id: GO_REF:0000117
qualifier: enables
review:
summary: ARBA machine-learning electronic annotation assigning the very general
molecular function "hydrolase activity". This is correct in essence (patatin/PNPLA
proteins are hydrolases) but is uninformatively broad given that the patatin
domain reliably confers a specific class of activity, namely carboxylic ester
(acyl) hydrolysis of lipids.
action: MODIFY
reason: The patatin/PNPLA domain is a lipid acyl hydrolase module that cleaves
carboxylic ester bonds of glycerolipids using a Ser-Asp catalytic dyad
[PMID:12779324]. "Hydrolase activity" (GO:0016787) is therefore correct but far
too general; a more informative and equally well-supported term is "carboxylic
ester hydrolase activity" (GO:0052689), the parent of the lipase/phospholipase/acylglycerol-lipase
activities characteristic of this family. The UniProt entry's own family-level
FUNCTION text describes non-specific lipolytic acyl hydrolase activity hydrolyzing
phospholipids and galactolipids. More substrate-specific functions are in fact
asserted for this protein by GO_Central as IBA (phylogenetic) annotations -
glycerophospholipase activity (GO:0004620) and monoacylglycerol lipase activity
(GO:0047372) - which are visible in AmiGO/GOlr but were not returned by the QuickGO
GOA pull that seeded this review (see reference GO_REF:0000033 and the AmiGO record
at http://amigo.geneontology.org/amigo/gene_product/UniProtKB:A0A3B6GK97). Because
those IBA lipase terms already capture the specific activity out of band, this
generic ARBA "hydrolase activity" annotation is best modified to their immediate
informative parent, "carboxylic ester hydrolase activity" (GO:0052689), rather than
left at the root-level hydrolase term or duplicated into the specific IBA terms.
IMPORTANT CAVEAT - the family-level MF may not hold for this specific deposited
sequence. A reproducible bioinformatics analysis (file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md)
shows that the modeled 302-aa protein places in the pPLAII subfamily but LACKS the
entire N-terminal half of the patatin catalytic domain - both the oxyanion glycine-rich
block (DGGG) and the catalytic-serine nucleophile elbow (G-T-S-T-G) are absent (the
sequence has no G-x-S-x-G motif at all), although it retains the catalytic Asp. As
modeled it is therefore predicted catalytically INACTIVE (no nucleophile), most likely
reflecting an incomplete/incorrect gene model (~100-130 aa shorter than orthologs)
rather than - but not excluding - a genuine degenerate pseudo-enzyme. The IBA lipase
calls were propagated phylogenetically and do not verify active-site integrity. The
MODIFY to carboxylic ester hydrolase activity is retained as the correct FAMILY-level
term, but with this explicit caveat that the activity is not verifiable on, and may be
absent from, the current sequence model.
proposed_replacement_terms:
- id: GO:0052689
label: carboxylic ester hydrolase activity
supported_by:
- reference_id: PMID:12779324
supporting_text: Patatin is a nonspecific lipid acyl hydrolase
- reference_id: GO_REF:0000033
supporting_text: Annotation inferences using phylogenetic trees
- reference_id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md
supporting_text: the modeled 302-aa protein places in the pPLAII subfamily but LACKS
the entire N-terminal half of the patatin catalytic domain - both the oxyanion
glycine-rich block (DGGG) and the catalytic-serine nucleophile elbow (G-T-S-T-G)
are absent
- reference_id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-deep-research-falcon.md
supporting_text: PNPLA/patatin enzymes use a Ser-Asp catalytic dyad rather than
the classical Ser-His-Asp triad of many alpha/beta-hydrolases
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO
terms
findings: []
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: InterPro2GO mapping reference. Confirmed via the EBI InterPro API
that IPR002641 (Patatin-like phospholipase domain) maps to GO:0006629 lipid
metabolic process, matching the GOA annotation.
- id: GO_REF:0000117
title: Electronic Gene Ontology annotations created by ARBA machine learning models
findings: []
reference_review:
relevance: MEDIUM
correctness: VERIFIED
review_notes: ARBA electronic-annotation reference. The assigned term (hydrolase
activity) is correct but under-specific for a patatin-family lipid acyl hydrolase;
see review action MODIFY.
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings:
- statement: 'GO_Central assigns this protein two IBA (phylogenetic) molecular-function
annotations confirming lipase activity: GO:0004620 glycerophospholipase activity
and GO:0047372 monoacylglycerol lipase activity (both ECO:0000318, GO_REF:0000033,
assigned 2017-02-28). These are present in AmiGO/GOlr but were NOT returned by
the QuickGO GOA pull used to seed this review, so they are recorded here as
out-of-band evidence rather than as existing_annotations entries.'
supporting_text: Annotation inferences using phylogenetic trees
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: 'GO_Central phylogenetic (PAINT/IBA) annotation reference. Verified
in AmiGO/GOlr (http://amigo.geneontology.org/amigo/gene_product/UniProtKB:A0A3B6GK97)
that this protein carries IBA annotations GO:0004620 glycerophospholipase activity
and GO:0047372 monoacylglycerol lipase activity. These manually-reviewed
phylogenetic annotations support the lipase interpretation but are missing from
the QuickGO GOA seed, hence treated as out-of-band knowledge.'
- id: PMID:12779324
title: 'The crystal structure, mutagenesis, and activity studies reveal that patatin
is a lipid acyl hydrolase with a Ser-Asp catalytic dyad'
findings:
- statement: Patatin is a lipid acyl hydrolase that uses a non-classical Ser-Asp
catalytic dyad rather than the canonical Ser-His-Asp triad; this defines the
catalytic mechanism of the patatin/PNPLA domain family to which this wheat protein
belongs.
supporting_text: patatin has a Ser-Asp catalytic dyad
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: PubMed-verified (PMID:12779324). Foundational structural/mechanistic
paper for the patatin/PNPLA family and the primary support for the proposed MF
term change (GO:0052689); informs the molecular function inference at the family
level rather than this specific wheat locus.
- id: PMID:16297072
title: A pathogen-inducible patatin-like lipid acyl hydrolase facilitates fungal
and bacterial host colonization in Arabidopsis
findings:
- statement: Plant patatin-like proteins (e.g. Arabidopsis PLP2) are pathogen-inducible
cytoplasmic lipid acyl hydrolases with broad substrate specificity that contribute
to lipid-based signaling in plant-pathogen interactions; this is the basis for
the family-level "plant defense" association but has not been shown for this
wheat protein.
supporting_text: PLP2 encodes a cytoplasmic lipid acyl hydrolase with wide substrate
specificity
reference_review:
relevance: LOW
correctness: VERIFIED
review_notes: PubMed-verified (PMID:16297072). Provides family/context for the
plant-defense keyword propagated to this entry; not specific to this wheat locus.
- id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-deep-research-falcon.md
title: 'Deep research report: PNPLA domain-containing protein A0A3B6GK97 in wheat
(Triticum aestivum) - family-level functional annotation from scientific literature'
findings:
- statement: Plant PNPLA/patatin proteins function as calcium-independent phospholipases
with lipase/phospholipase A-type activities. Their primary roles include lipid
mobilization during seed germination, membrane phospholipid turnover, and stress
adaptation. Substrate specificity includes phosphatidylcholine, phosphatidylserine,
triacylglycerols, and lysophospholipids.
supporting_text: The best-supported plant functions are lipid mobilization during
seed germination, initiation of storage-oil breakdown, membrane phospholipid
turnover, and remodeling of LD surfaces to allow access of TAG lipases
- statement: No direct literature exists for A0A3B6GK97; all functional inferences
are family-level, drawn from rice OsPLB, Arabidopsis PLP/pPLA, rapeseed patatin-like
lipase, and potato patatin studies.
supporting_text: Direct literature on the wheat protein A0A3B6GK97 is not available
in the current scientific literature
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Edison/falcon deep research report. Comprehensive family-level review
of plant PNPLA/patatin proteins. No gene-specific literature exists for this
wheat protein. All citations are DOI-based references to real publications (confirmed
by cross-referencing DOIs). Reinforces and is consistent with the subfamily
placement and functional inference from the in-repo bioinformatics analysis.
- id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md
title: 'Bioinformatics analysis: pPLA subfamily placement and catalytic-site integrity
of A0A3B6GK97'
findings:
- statement: By sequence identity (42-50% to pPLAII / rice pPLAs vs ~23% to pPLAIII and
~16% to pPLAI) and neighbour-joining placement, A0A3B6GK97 belongs to the pPLAII
subfamily of plant patatin-related phospholipase A - the soluble lipid-acyl-hydrolase
(defense/wounding/stress) clade - not pPLAIII (galactolipase/growth) or pPLAI
(iPLA2-like). The single-domain architecture and this placement make a membrane
trafficking role very unlikely.
supporting_text: A0A3B6GK97 belongs to the pPLAII subfamily
- statement: The modeled 302-aa sequence LACKS the N-terminal half of the patatin catalytic
domain - both the oxyanion glycine-rich block (DGGG) and the catalytic-serine
nucleophile elbow (G-T-S-T-G) are absent (zero G-x-S-x-G motifs in 302 aa), while the
catalytic Asp is retained. As modeled the protein is predicted catalytically inactive;
most parsimoniously an incomplete/incorrect gene model, though a genuine degenerate
pseudo-enzyme cannot be excluded from sequence alone.
supporting_text: the deposited 302-aa model lacks the N-terminal catalytic core
reference_review:
relevance: HIGH
correctness: VERIFIED
review_notes: Reproducible in-repo analysis (MSA of 13 characterized plant pPLAs +
query; FAMSA/BioPython; input-driven control included). Establishes pPLAII placement
and the absence of the catalytic serine in the deposited model.
core_functions:
- description: Predicted lipid acyl hydrolase of the plant patatin-related phospholipase
A pPLAII subfamily (soluble acyl hydrolase / defense-stress clade), acting on
glycerolipids in lipid metabolism. GO_Central IBA annotations specify glycerophospholipase
(GO:0004620) and monoacylglycerol lipase (GO:0047372) activities; carboxylic ester
hydrolase activity is used here as the unifying parent term. CAVEAT - this is the
family/subfamily-level function; the deposited 302-aa model itself lacks the catalytic-serine
nucleophile elbow (G-T-S-T-G) and oxyanion (DGGG) and is predicted inactive as modeled
(likely a truncated gene model), so the activity is inferred for the gene/subfamily, not
confirmed for the current sequence. Based on domain homology, phylogenetic (IBA) inference,
and in-repo bioinformatics; no direct experimental data for this specific protein.
molecular_function:
id: GO:0052689
label: carboxylic ester hydrolase activity
directly_involved_in:
- id: GO:0006629
label: lipid metabolic process
supported_by:
- reference_id: PMID:12779324
supporting_text: Patatin is a nonspecific lipid acyl hydrolase
- reference_id: GO_REF:0000033
supporting_text: Annotation inferences using phylogenetic trees
- reference_id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-bioinformatics/RESULTS.md
supporting_text: A0A3B6GK97 belongs to the pPLAII subfamily
- reference_id: file:WHEAT/A0A3B6GK97/A0A3B6GK97-deep-research-falcon.md
supporting_text: Plant PNPLA/patatin proteins function as calcium-independent
phospholipases with lipase/phospholipase A-type activities acting on phospholipids,
galactolipids, triacylglycerols, and lysophospholipids
proposed_new_terms: []
suggested_questions:
- question: What is the substrate specificity of this wheat patatin-like protein (phospholipids
vs. galactolipids vs. acylglycerols), and which acyl-ester bonds (sn-1/sn-2) does
it preferentially hydrolyze?
- question: Is this gene (TraesCS3D02G033600) transcriptionally induced upon pathogen
challenge or abiotic stress in wheat, as seen for defense-related patatin-like
proteins in other plants?
- question: Is the deposited 302-aa model (which lacks the N-terminal oxyanion DGGG and
catalytic-serine G-T-S-T-G motifs) an incomplete/incorrect gene model, or does the
locus genuinely encode a catalytically dead pPLAII pseudo-enzyme? (Check the 3A/3B/3D
homoeologs, alternative gene models, and RNA-seq evidence for a missing 5' exon.)
suggested_experiments:
- description: Express and purify the recombinant protein and assay lipid acyl hydrolase
activity against defined substrates (phospholipids, galactolipids, mono/di-acylglycerols),
with catalytic-Ser mutagenesis to confirm the predicted Ser-Asp dyad.
experiment_type: in vitro enzyme assay
- description: Profile expression of TraesCS3D02G033600 across tissues and in response
to fungal/bacterial pathogen infection to test a possible defense role.
experiment_type: transcriptomics
- description: Verify/curate the gene model - inspect the genomic locus, splice junctions
and RNA-seq coverage at the 5' end and compare with the 3A/3B/3D homoeologs to determine
whether the missing N-terminal catalytic exon (oxyanion + catalytic Ser) reflects a gene
annotation error or a true loss of the catalytic serine.
experiment_type: gene model curation / comparative genomics