AADACL4 is a 407-residue member of the 'GDXG' lipolytic enzyme family and one of five human arylacetamide deacetylase-related proteins: AADAC, NCEH1/AADACL1 and AADACL2 lie on chromosome 3, while AADACL3 and AADACL4 sit adjacent to one another at 1p36.21 and are the closest pair, sharing both length and catalytic-residue register. It has the alpha/beta-hydrolase fold-3 architecture of the family with an intact Ser-Asp-His catalytic triad (Ser193 in a GESVG nucleophile elbow, Asp347, His377) and the HGG oxyanion-hole motif that stabilises the acyl-enzyme intermediate, so it is predicted to be a functional carboxylic ester hydrolase rather than a catalytically dead fold relative. A hydrophobic N-terminal segment is predicted to act as a signal anchor that places the catalytic domain, together with two predicted N-glycosylation sites, on the lumenal or extracellular face of a membrane; the characterised relatives sit in the endoplasmic reticulum membrane (AADAC) or the plasma membrane (NCEH1), while AADACL2 is secreted, so which membrane AADACL4 occupies is not established. No substrate, inhibitor, knockout phenotype or biochemical assay has been reported for the protein, and UniProt records it as inferred from homology rather than detected. Transcript expression is described as enhanced in choroid, with broader low-level expression across tissues including omental fat.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0016787 hydrolase activity | IBA GO_REF:0000033 | MODIFY | Summary: Correct, correctly scoped and validly transferred - and redundant. The donor node is functionally heterogeneous, and donor-by-donor testing shows bare hydrolase activity is not merely a cautious call there but the exact least common ancestor of the donor set, with no candidate term below it surviving every donor. What makes the row replaceable is therefore not granularity but redundancy: AADACL4's own subfamily signature already supplies the specific ester-hydrolase term on this same record. Reason: All three human AADAC-family paralogs carry this row byte for byte: AADACL2, AADACL3 and AADACL4 each have GO:0016787 by IBA from GO_REF:0000033, transferred from PANTHER node PTN009058710, with the same 17 WITH/FROM tokens. That equality is measured for all three, not assumed, from two independent sources that have to agree: the committed GOA TSVs, and a per-accession QuickGO fetch for Q6P093, Q5VUY0 and Q5VUY2. It therefore has one correct treatment, and the donor set decides what that is. All 17 tokens were resolved and each donor's chemistry and nucleophile read off its own EC numbers, its own curated GO annotations classified by fetched ontology ancestry, and its own ACT_SITE features. GO:0016787 is true of 16 of the 16 donor proteins. GO:0052689 carboxylic ester hydrolase activity is true of 14 and false of 2: the kynurenine formamidases mouse Afmid (Q8K4H1) and yeast BNA7 (Q04066), EC 3.5.1.9, carry GO:0004061 arylformamidase activity, which sits under GO:0016810 on the carbon-nitrogen branch and not under the ester branch, by IMP and IDA respectively. GO:0017171 serine hydrolase activity is true of 15 and false of 1: soybean HIDH's nucleophile-elbow residue is Thr164. That last call rests on fold position rather than on a UniProt label - UniProt describes HIDH's ACT_SITE 164 as a proton acceptor (ECO:0000305) rather than naming a nucleophile, and 164 is the N-terminal-most member of a checked Thr-Asp-His triad - but the sequence corroborates it independently: 15 of the 16 donors read G-x-S-x-G at the nucleophile elbow while HIDH alone reads GETSG, so the elbow serine is substituted. The verdict does not depend on that rule: downgrading HIDH to undetermined still leaves GO:0017171 untrue of every donor, and downgrading every positionally-inferred nucleophile leaves it supportable for only the two donors UniProt labels explicitly. The two refutations lie on different axes, so neither candidate can be rescued by choosing the other, and because GO:0016788 and GO:0016810 are siblings whose only common ancestor below catalytic activity is GO:0016787, the term PAINT chose is exactly the lowest common ancestor of its donors. There is consequently no granularity and no term-scoping defect to correct on this row in any of the three genes, which is why root_cause is EVIDENCE_CIRCULAR_OR_REDUNDANT and no failure mode is recorded: the target already has stronger direct evidence, and the propagation itself did not fail. GRANULARITY_MISMATCH is deliberately not recorded: read literally its definition would fit any general term on any record, but the slot describes the biological shape of a propagation issue and this propagation has none, so the campaign rule applies - ask whether the term is the LCA of its donors, and reserve the mode for donors that agree while the term still sits above them. The schema's enum description does not yet distinguish the two readings and would be worth clarifying: all three paralogs now encode the row on the propagation-shape reading, which the enum text does not itself state. For AADACL4 that stronger evidence is the narrower arylacetamide-deacetylase signature (InterPro IPR017157, PIRSF037251), whose GO:0052689 is already on this record, backed by a catalytic apparatus that is demonstrably intact: the annotated Ser193, Asp347 and His377 really are Ser, Asp and His, the nucleophile sits in a canonical GESVG elbow, the HGG oxyanion-hole motif is present at 119-121, and all seven AADAC-family relatives project their own annotated triads onto exactly those three residues. So this row adds only a redundant ancestor of a term the record already has, and the replacement term is a statement about what AADACL4's annotation set should contain rather than a claim that PTN009058710 could itself license the child term. Neither GO:0016787 nor GO:0016020 is in gocheck_do_not_annotate (both are usage Unrestricted), so this rests on redundancy, not on a rule violation. GO:0017171 is separately true of AADACL4 on its own residues but cannot be reached from this row either; it is true of every donor PAINT cites at the family node PTN009058713 and IDA-supported by all three of them, so it is raised as a PAINT node-placement recommendation in suggested_questions. Propagation Review Root cause: EVIDENCE CIRCULAR OR REDUNDANT Sources checked: PANTHER:PTN009058710 · ancestral GDXG lipolytic-enzyme node SUPPORTS TRANSFER Not self-referential; Q5VUY2 is absent from the WITH/FROM list. GO:0016787 is true of all 16 donor proteins and is their exact least common ancestor, so this node licenses the term it was used for and nothing more specific. UniProtKB:Q5NUF3 · soybean HIDH, 2-hydroxyisoflavanone dehydratase SUPPORTS TRANSFER Supports GO:0016787 rather than blocking it. HIDH is bifunctional, carrying EC 3.1.1.1 and a GO:0106435 carboxylesterase activity IDA alongside EC 4.2.1.105, so it is a genuine if physiologically minor ester hydrolase and not a pure lyase. It is the single donor that refutes GO:0017171: UniProt annotates ACT_SITE 164 as a proton acceptor (ECO:0000305) rather than naming a nucleophile, so the call rests on fold position, but the elbow pentapeptide reads GETSG against G-x-S-x-G in the other 15 donors, and the verdict survives downgrading the call to undetermined. It matches neither IPR017157 nor the family node. MGI:MGI:2448704 · mouse Afmid, kynurenine formamidase SUPPORTS SOURCE BUT NOT TARGET EC 3.5.1.9 with GO:0004061 arylformamidase activity by IMP, on the GO:0016810 carbon-nitrogen branch rather than the ester branch, so it is one of the two donors that keep GO:0052689 off this node. It does not block a mechanism term: UniProt names its own nucleophile Ser162. SGD:S000002836 · yeast BNA7, kynurenine formamidase SUPPORTS SOURCE BUT NOT TARGET The second amide hydrolase, EC 3.5.1.9 with GO:0004061 by IDA. It resolves cleanly through xref:sgd-S000002836 to Q04066, whose ACT_SITE 110 UniProt labels the nucleophile and which reads as Ser, so it too is a serine hydrolase. UniProtKB:P22760 · human AADAC, arylacetamide deacetylase SUPPORTS TRANSFER A characterised EC 3.1.1.3 ester hydrolase in the same clade as AADACL4, holding GO:0017171 by IDA. It is also a donor at the family node PTN009058713, which is where that mechanism term can safely descend. UniProtKB:Q9HTI0 · probable lipolytic enzyme, Pseudomonas aeruginosa SOURCE WEAK OR INFERRED The one donor with no reviewed entry, so its name is not usable as evidence and its single ACT_SITE is ECO:0000256. Its curated GO:0047619 acylcarnitine hydrolase activity is nevertheless IDA, so it still counts as an ester hydrolase donor. Proposed replacements: carboxylic ester hydrolase activity Supporting Evidence: file:human/AADACL2/AADACL2-bioinformatics/NODE_PTN009058710.md No donor refutes `GO:0016787`, and every more specific candidate is refuted by at least one donor. file:human/AADACL2/AADACL2-bioinformatics/NODE_PTN009058710.md GO:0016787 hydrolase activity: TRUE 16, FALSE 0, UNDETERMINED 0 file:human/AADACL2/AADACL2-bioinformatics/NODE_PTN009058710.md `GO:0016787` is not merely unrefuted, it is the exact lowest common ancestor of this donor set. file:human/AADACL4/AADACL4-bioinformatics/RESULTS.md amide hydrolase (EC 3.5.-): **2** file:human/AADACL4/AADACL4-bioinformatics/RESULTS.md Triad residues in sequence order: **SDH** file:human/AADACL4/AADACL4-bioinformatics/RESULTS.md Nucleophile elbow pentapeptide around Ser193: `GESVG` file:human/AADACL2/AADACL2-bioinformatics/NODE_PTN009058710.md Fifteen of the sixteen donors read **G-x-S-x-G** at the elbow — `GDSAG` in twelve of them, `GQSAG` in ICME, `GHSAG` in Afmid and `GHSVG` in BNA7 — while HIDH alone reads **`GETSG`** file:human/AADACL2/AADACL2-bioinformatics/NODE_PTN009058710.md only_the_refuting_donor_undetermined: TRUE 15, FALSE 0, UNDETERMINED 1, true_of_every_donor=False file:human/AADACL2/AADACL2-bioinformatics/NODE_PTN009058710.md all three carry `GO:0017171` by IDA |
| GO:0016020 membrane | IBA GO_REF:0000033 | ACCEPT | Summary: Accept, and accept it at this general level. The donors are the AADAC/NCEH1 clade, all single-pass type II membrane proteins, but they disagree about which membrane, so membrane is the correct call rather than a lapse into an over-general parent. Reason: This is the narrower of the two PANTHER nodes used for AADACL4: PTN009058713 is supported by mouse Aadac (Q99PG0), mouse Nceh1 (Q8BLF1) and human AADAC (P22760), all of which are UniProt single-pass type II membrane proteins detected at protein level, and AADACL4 carries an equivalent predicted N-terminal signal anchor (its own TRANSMEM 5-25) with its catalytic domain and both predicted N-glycosylation sites on the far side. The is_active_in qualifier is appropriate for a membrane-anchored enzyme. The term should not be refined: the donors resolve to four distinct specific locations - endoplasmic reticulum membrane and microsome membrane for the two Aadac orthologues, cell membrane and microsome for Nceh1 - so choosing endoplasmic reticulum membrane or plasma membrane for AADACL4 would mean picking one donor over the other with no AADACL4 data to justify it. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN009058713 · AADAC/NCEH1 clade node SUPPORTS TRANSFER A different, narrower node than the one used for the hydrolase-activity row; not self-referential. UniProtKB:P22760 · human AADAC SUPPORTS TRANSFER Endoplasmic reticulum and microsome membrane, single-pass type II. MGI:MGI:1915008 · mouse Aadac SUPPORTS TRANSFER Endoplasmic reticulum and microsome membrane, single-pass type II. MGI:MGI:2443191 · mouse Nceh1 SUPPORTS TRANSFER Cell membrane and microsome, single-pass type II. Supports membrane residence but disagrees with the Aadac donors on the specific compartment, which is why the general term is retained. Supporting Evidence: file:human/AADACL4/AADACL4-bioinformatics/RESULTS.md Distinct specific locations across the donors: **4** file:human/AADACL4/AADACL4-uniprot.txt Helical; Signal-anchor for type II membrane protein |
| GO:0016020 membrane | IEA GO_REF:0000120 | ACCEPT | Summary: The same conclusion as the IBA row, reached from AADACL4's own predicted topology rather than from donor localisation. Kept, with the caveat that its basis is the softer of the two and that the closest paralogs do not share the feature call. Reason: This row traces to the UniProt subcellular-location line, which is an ECO:0000305 curator inference over an ECO:0000255 TRANSMEM prediction; SL-0162, ARBA00028763 and IPR017157 are the controlled-vocabulary, automatic-annotation and family handles for that same statement. The conclusion agrees with the independently derived IBA row and with the family, so it is retained. What is worth recording is how soft the underlying feature call is: among paralogs that share the catalytic register exactly, UniProt calls a signal anchor for AADACL4, a cleaved signal peptide for AADACL2 (which is consequently annotated Secreted), and nothing at all for AADACL3 despite a comparably hydrophobic N-terminal segment. All of those are sequence-analysis predictions, and mean hydropathy cannot discriminate a cleaved signal peptide from an uncleaved type II anchor, so no attempt was made to overturn the call from sequence alone. The two membrane rows are only partly independent: the IBA leans on experimentally localised donors, whereas this row leans on AADACL4's own topology prediction plus family similarity. So they are not simply duplicates, but neither contributes experimental evidence for AADACL4 itself, and this is the weaker of the two. Propagation Review Root cause: NO FAILURE CORE Sources checked: UniProtKB-SubCell:SL-0162 · UniProt subcellular location - Membrane SOURCE WEAK OR INFERRED Encodes an ECO:0000305 curator inference over an ECO:0000255 topology prediction; no experimental localisation exists for AADACL4. InterPro:IPR017157 · Arylacetamide deacetylase family signature SUPPORTS TRANSFER The subfamily is membrane-anchored or secreted throughout, which is consistent with membrane but does not by itself pick a compartment. Supporting Evidence: file:human/AADACL4/AADACL4-uniprot.txt SUBCELLULAR LOCATION: Membrane {ECO:0000305}; Single-pass type II |
| GO:0016787 hydrolase activity | IEA GO_REF:0000002 | MODIFY | Summary: Redundant general parent, and correctly scoped for its own signature. IPR013094 is the generic Abhydrolase_3 domain, which can only be mapped to hydrolase activity, while the same protein also matches the subfamily-specific IPR017157 that yields the informative term. Reason: InterPro2GO maps IPR013094 (alpha/beta hydrolase fold-3 domain) to GO:0016787 because that domain occurs in enzymes with different bond specificities; the mapping is correct for the domain and redundant for the protein. AADACL4 also matches IPR017157 (arylacetamide deacetylase) and PIRSF037251, which support the ester-bond specialisation, and its catalytic triad and oxyanion hole are intact, so GO:0052689 - already present on this protein from IPR017157 - is the term the evidence supports. As with the IBA hydrolase row, this is a granularity replacement, not a claim that the annotation is wrong - and specifically not a recommendation to change the IPR013094-to-GO:0016787 InterPro2GO mapping itself. That domain genuinely does occur in amidases as well as esterases, and in soybean HIDH, whose nucleophile is a threonine and whose physiologically important reaction is a dehydration, so the mapping is right for the domain and should stay. The replacement is a statement about what AADACL4's own annotation set should contain, where a subfamily-level signature is available too, and the classification matches the IBA row above: EVIDENCE_CIRCULAR_OR_REDUNDANT, with no failure mode, because the signature's own scope is correct and only its redundancy on this record is at issue: the fold genuinely spans amidases, esterases and a threonine-nucleophile dehydratase, so GO:0016787 is the right mapping for it. GRANULARITY_MISMATCH is deliberately not recorded here for the same reason as on the IBA row - the mode describes the biological shape of a propagation issue, and a signature whose own member set is heterogeneous has no granularity defect to record. Propagation Review Root cause: EVIDENCE CIRCULAR OR REDUNDANT Sources checked: InterPro:IPR013094 · AB_hydrolase_3 domain CIRCULAR OR REDUNDANT A pan-family fold signature whose GO mapping is necessarily the general hydrolase parent; adds no information beyond the IPR017157-derived GO:0052689 row on the same protein. Proposed replacements: carboxylic ester hydrolase activity Supporting Evidence: file:human/AADACL4/AADACL4-bioinformatics/RESULTS.md Residues 119-121: `HGG` (the GDXG oxyanion-hole motif) |
| GO:0052689 carboxylic ester hydrolase activity | IEA GO_REF:0000002 | ACCEPT | Summary: The best-supported statement about AADACL4 and the one molecular-function term worth keeping. The subfamily signature is backed by a demonstrably complete GDXG catalytic apparatus, though no substrate has ever been tested. Reason: IPR017157 is the arylacetamide-deacetylase family signature rather than a generic fold, and the activity it implies was checked against the sequence rather than taken on trust. AADACL4's UniProt active-site positions 193, 347 and 377 are genuinely Ser, Asp and His; Ser193 lies in a canonical GESVG nucleophile elbow; the HGG oxyanion-hole motif is present at 119-121; and the annotated triads of all seven AADAC-family relatives - AADACL3, AADACL2, human, rat and mouse AADAC, human and mouse NCEH1 - project onto exactly those three AADACL4 residues by global alignment with matching residue identity. This rules out the fold-retaining pseudoenzyme reading, so the annotation is a statement about an intact active site rather than a domain name transcribed into an activity. It remains an unverified homology inference: no substrate, inhibitor or activity assay has been reported, which is why the term is kept at this substrate-agnostic level and no child term is proposed. It is also the term the two general hydrolase-activity rows on this record should collapse onto, and the core molecular function recorded for AADACL2 and AADACL3 as well, whose catalytic registers are identical to AADACL4's. Propagation Review Root cause: NO FAILURE CORE Sources checked: InterPro:IPR017157 · Arylacetamide deacetylase family signature SUPPORTS TRANSFER Subfamily-level rather than fold-level, and independently corroborated by the intact Ser193-Asp347-His377 triad and HGG oxyanion hole. Supporting Evidence: file:human/AADACL4/AADACL4-bioinformatics/RESULTS.md Triad residues in sequence order: **SDH** file:human/AADACL4/AADACL4-uniprot.txt Belongs to the 'GDXG' lipolytic enzyme family. PMID:21696217 Candidate endogenous substrates, selective inhibitors, or knockout mice have not, to our knowledge, been described for AADAC or the related enzymes AADACL2 and AADACL4. |
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Download this section (compressed HTML)Q: Should GO:0017171 serine hydrolase activity move from the ortholog-specific PANTHER nodes PTN002745055 (AADAC) and PTN002745068 (NCEH1) down to the shared family node PTN009058713? Measured against that node's own donors, the term is true of all three of them - human AADAC, mouse Aadac and mouse Nceh1 - and all three hold it by IDA, whereas at the far deeper PTN009058710 that AADACL2, AADACL3 and AADACL4 actually inherit their only activity term from, it is refuted by soybean HIDH's threonine at the nucleophile elbow. One node move would give all three paralogs a mechanism term they currently inherit from nothing, and the reciprocal half is worth reporting too: GO:0016020 membrane sits at that same family node although the type-II signal anchor it rests on is exactly the feature that varies across the three paralogs.
Q: Is the AADACL4 protein expressed at all in human tissue, and if so where? UniProt classifies it as inferred from homology and Pharos as Tdark, yet the transcript is reported as choroid-enhanced with broad low-level expression, so a targeted proteomic or immunohistochemical detection would be the first thing worth doing.
Q: Is the AADACL4 N-terminal hydrophobic segment an uncleaved type II signal anchor or a cleaved signal peptide? UniProt makes three different calls across three paralogs that share the catalytic register exactly - signal anchor for AADACL4, cleaved signal peptide plus Secreted for AADACL2, and no feature at all for AADACL3 despite a comparably hydrophobic segment - and all of them are ECO:0000255 predictions. The AADACL3 gap in particular looks like a UniProt annotation inconsistency worth reporting upstream.
Q: Which membrane does AADACL4 occupy? The phylogenetic annotation's own donors split between the endoplasmic reticulum membrane (AADAC orthologues) and the plasma membrane (NCEH1), which is why the annotation stops at membrane.
Q: Why does UniProt cross-reference PAN-GO as contributing zero evolutionary-model annotations for Q5VUY2 while GOA carries two GO_Central IBA rows for the same protein? Clarifying whether the human PAN-GO effort deliberately declined to annotate AADACL4 would say how much weight the IBA rows should carry.
Q: Chicken AADACL4B is upregulated during keratinocyte differentiation and enriched in interscale epidermis, and the secreted human paralog AADACL2 is skin-enriched. Is the avian gene a true orthologue of human AADACL4 or a bird-specific duplicate, and is there a shared role for this subfamily in epidermal lipid ester turnover?
Suggested experts: Lachner J
Q: Does AADACL4 carry any activity toward arylacetamide xenobiotics, given that the family's founder AADAC deacetylates flutamide and phenacetin? A negative result would be as useful as a positive one for scoping the family's pharmacological relevance.
Suggested experts: Long JZ, Cravatt BF
Experiment: Apply activity-based protein profiling with a fluorophosphonate probe to lysates from choroid or adipose tissue and to cells overexpressing tagged wild-type AADACL4 and an S193A mutant, then identify labelled species by mass spectrometry. This platform already labels the large majority of mammalian metabolic serine hydrolases, so a failure to label wild-type AADACL4 would itself be informative about whether the intact triad is used.
Hypothesis: AADACL4 is a catalytically active serine hydrolase, so its Ser193 nucleophile should be labelled by an active-site-directed fluorophosphonate probe in a tissue that expresses it, and the S193A mutant should not be.
Type: activity-based protein profiling
Experiment: Express and purify the lumenal domain and assay it against a graded panel: para-nitrophenyl esters of increasing acyl chain length, tributyrin and triolein, cholesteryl oleate, 1-O-hexadecyl-2-acetyl-sn-glycerol, and the arylacetamide drugs flutamide and phenacetin. Run the S193A, D347A and H377A mutants in parallel so that any activity observed is attributable to the triad rather than to a contaminating esterase.
Hypothesis: AADACL4 hydrolyses carboxylic esters, with a substrate preference that can be placed relative to AADAC (arylacetamide xenobiotics, triacylglycerol) and NCEH1 (cholesteryl esters, 2-acetyl monoalkylglycerol ether).
Type: in vitro enzyme assay
Experiment: Express epitope-tagged AADACL4 with tags at each terminus and test topology by protease-protection of sealed microsomes and by selective permeabilisation immunofluorescence. In parallel test glycan occupancy at the two predicted sites by PNGase F sensitivity and by N168Q/N269Q substitution, since glycosylation is only available to a lumenal or extracellular domain. This distinguishes the signal-anchor and cleaved-signal-peptide readings that UniProt applies inconsistently across the paralogs, and pairs with co-staining for endoplasmic reticulum and plasma-membrane markers to settle which membrane.
Hypothesis: AADACL4 is a type II single-pass membrane protein whose catalytic domain faces the lumen or the extracellular space, in which case Asn168 and Asn269 should be N-glycosylated.
Type: membrane topology and glycosylation mapping
Experiment: Knock out AADACL4 in a model expressing it - guided first by a protein-level detection experiment, since the transcript-level choroid enrichment is the only current lead - and profile neutral lipids, ether lipids and cholesteryl esters by untargeted lipidomics against wild type, using an S193A knock-in as a catalytically dead control to separate scaffolding from catalytic contributions.
Hypothesis: Loss of AADACL4 perturbs a lipid ester pool in the tissue where it is expressed.
Type: knockout lipidomics
What is not known — curated, literature-grounded statements of the open unknowns (the inverse of core functions).
Gap: No substrate is known for AADACL4 - neither a physiological acyl donor nor an in vitro surrogate ester has been tested - so the activity cannot be refined below the substrate-agnostic parent term.
OPEN BIOLOGY MF_DARK
What is known: What is firmly established is the catalytic apparatus itself: Ser193 in a GESVG nucleophile elbow, Asp347, His377 and an HGG oxyanion hole, in register with the annotated triads of all seven AADAC-family relatives. The gap is about specificity, not about whether the protein can catalyse anything.
Significance: The family spans very different chemistries - arylacetamide xenobiotics and triacylglycerol for AADAC, cholesteryl esters and 2-acetyl monoalkylglycerol ether for NCEH1 - so without a substrate the annotation cannot say which of those biologies, if any, AADACL4 participates in.
What would resolve it: A graded in vitro substrate panel against the purified lumenal domain, with S193A, D347A and H377A controls, plus activity-based profiling with a fluorophosphonate probe to confirm the nucleophile is used at all.
Provenance (the field's own admissions):
Gap: Which membrane AADACL4 occupies, and whether its N-terminal hydrophobic segment is an uncleaved type II signal anchor at all rather than a cleaved signal peptide, are both undetermined.
OPEN BIOLOGYCURATION CC_DARK
What is known: The segment itself is real and strongly hydrophobic, and every characterised member of the subfamily is either membrane-anchored or secreted, so an association with the secretory pathway is not in doubt. What is undetermined is the topology and the compartment.
Significance: An endoplasmic reticulum enzyme, a cell-surface enzyme and a secreted enzyme act on different substrate pools, so the compartment is a prerequisite for interpreting any activity that is found. The curation component is separable and actionable: UniProt makes three different N-terminal calls across AADACL4, AADACL2 and AADACL3 despite identical catalytic registers, all from sequence analysis alone.
What would resolve it: Protease-protection and selective-permeabilisation topology assays, together with glycan-occupancy tests at the two predicted N-glycosylation sites, which are only accessible to a lumenal or extracellular domain; plus co-staining against endoplasmic reticulum and plasma-membrane markers.
Provenance (the field's own admissions):
Gap: No biological process is known for AADACL4, and it has no protein-level detection: there is no cell or tissue in which the protein has been shown to be present, no loss-of- function phenotype, and no pathway assignment.
OPEN BIOLOGY BP_DARK
What is known: Transcript-level expression is documented, with choroid enhancement and broad low-level expression, and the gene is protein-coding with a MANE-Select transcript and a CCDS entry. So the gap is not about whether the locus is expressed but about whether and where the protein acts.
Significance: GOA carries no biological-process annotation for AADACL4 at all, and that absence is correct rather than an oversight; a process term will only become available once the protein is detected somewhere and a substrate pool is identified.
What would resolve it: Targeted proteomic or immunohistochemical detection in the tissues with the highest transcript signal, followed by knockout lipidomics with a catalytically dead knock-in control.
Provenance (the field's own admissions):
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