Arsb

Summary: Sulfuric ester hydrolase activity is correct but is a broad parent of N-acetylgalactosamine-4-sulfatase activity (GO:0003943), which Arsb already carries by IEA, ISO and ISS.

Reason: Arsb is arylsulfatase B, the lysosomal N-acetylgalactosamine-4-sulfatase (EC 3.1.6.12) that removes 4-sulfate groups from dermatan and chondroitin sulfate. The PAINT inference assigns only the uninformative sulfatase class, so it is replaced by the specific activity. Policy applied across this re-review batch is that an uninformative broad parent of a specific activity or process the gene already carries is MODIFIED to that specific term; experimental rows stay at the curator's breadth unless the cited assay itself identifies the specific substrate.

Proposed replacements: N-acetylgalactosamine-4-sulfatase activity

Summary: The specific enzymatic activity of Arsb (EC 3.1.6.12). Well-established for the mammalian arylsulfatase B family.

Reason: Most precise MF term for Arsb. Supported by ISO from human/mouse orthologs and by biochemistry in the human review (IDA from PMID:18285341, PMID:19306108).

Summary: Lysosome is the primary and well-established compartment for Arsb function in glycosaminoglycan degradation.

Reason: Core cellular component annotation. Rat Arsb activity is measured in the mitochondrial-lysosomal (M-L) fraction of liver (PMID:8037) and rat MPS VI shows classical lysosomal storage of GAGs.

Summary: Sulfuric ester hydrolase activity is correct but is a broad parent of N-acetylgalactosamine-4-sulfatase activity (GO:0003943), which Arsb already carries by IEA, ISO and ISS.

Reason: Arsb is arylsulfatase B, the lysosomal N-acetylgalactosamine-4-sulfatase (EC 3.1.6.12) that removes 4-sulfate groups from dermatan and chondroitin sulfate. The electronic mapping assigns only the uninformative sulfatase class, so it is replaced by the specific activity. Policy applied across this re-review batch is that an uninformative broad parent of a specific activity or process the gene already carries is MODIFIED to that specific term; experimental rows stay at the curator's breadth unless the cited assay itself identifies the specific substrate.

Proposed replacements: N-acetylgalactosamine-4-sulfatase activity

Summary: Cell-surface localisation is directly demonstrated by IDA in rat liver (PMID:19536613); this IEA is consistent with UniProt SUBCELLULAR LOCATION statement.

Reason: Retain as a non-core (extra-lysosomal) localisation. Primary functional compartment is the lysosome, but cell-surface localisation is reproducibly observed in liver parenchymal and sinusoidal cell types and may participate in extracellular GAG remodelling.

Summary: Propagated from human ARSB, where IMP evidence (PMID:19306108) shows that silencing/overexpression of ARSB inversely modulates colonic epithelial cell migration via MMP9 and RhoA. Mechanism is via chondroitin sulfation and is conserved.

Reason: Supported by strong experimental evidence in the human ortholog and consistent with UniProt cross-species function summary. Non-core because it is a downstream consequence of Arsb GAG-desulfation activity in a specific tissue context, not the primary lysosomal catabolic function.

Summary: A core biological process for Arsb - removal of 4-sulfate groups from GalNAc-4-sulfate within chondroitin sulfate is an essential step in CSPG degradation, blocked in MPS VI.

Reason: Core biological process supported by the human ortholog IDA evidence (PMID:18285341) and by the MPS VI disease phenotype in rats (PMID:8575749) that shows accumulation of chondroitin/dermatan sulfate GAGs upon Arsb loss.

Summary: More specific descendant of GO:0010632; propagated from human ARSB where IMP evidence (PMID:19306108) directly measured colonic epithelial cell migration.

Reason: Tissue-specific non-core function conserved across mammalian orthologs. Retained but not part of the core enzymatic role.

Summary: ISO from human/mouse ARSB with is_active_in qualifier - captures that the enzyme is not merely located in but functionally active within the lysosome.

Reason: Consistent with the core lysosomal catabolic role. The is_active_in qualifier appropriately reflects that Arsb functions (not just localises) in the lysosome.

Summary: A core biological process for Arsb. Dermatan sulfate is one of the two primary substrates (with chondroitin-4-sulfate); its degradation is blocked in rat MPS VI.

Reason: Core function conserved from the mouse ortholog, whose donor annotation is an IMP in Arsb-deficient mice (PMID:24240681 per QuickGO), where loss of Arsb raised chondroitin-4-sulfate and sulfated GAG levels. Rat MPS VI (PMID:8575749) shows the same storage phenotype.

Summary: The mouse donor annotation for N-acetylgalactosamine-6-sulfatase activity is an MGI IMP from PMID:24240681 (QuickGO). The full text of that paper, now cached, describes ARSB only as an N-acetylgalactosamine-4-sulfatase acting on chondroitin-4-sulfate and dermatan sulfate, and contains no 6-sulfatase assay. N-acetylgalactosamine-6-sulfatase activity is the defining activity of the distinct enzyme GALNS.

Reason: The source annotation appears to have selected the 6-sulfatase term for a paper about the 4-sulfatase, so the error is in the donor record and is propagated to rat by ISO. Rat Arsb hydrolyzes 4-sulfate groups (EC 3.1.6.12), which is captured by the accepted GO:0003943 rows; no evidence supports a 6-sulfatase activity.

Summary: ISO propagation of the specific MF from mammalian orthologs; matches the IEA/EC-mapping and biochemistry.

Reason: Core molecular function; reinforces the IEA annotation from a different evidence source.

Summary: Duplicate of the IEA CSPG catabolic process annotation with ISO evidence.

Reason: Same rationale as the IEA version - core biological process.

Summary: Duplicate lysosome localisation with ISO evidence and located_in qualifier.

Reason: Same rationale as the IEA lysosome annotation - core localisation.

Summary: Propagated ISO annotation. MPS VI patients exhibit craniofacial abnormalities (part of the classic phenotype), so a loss-of-function link to anterior head development is defensible but indirect. Not a direct/core function; reflects the developmental consequence of GAG accumulation.

Reason: Non-core developmental phenotype secondary to loss of Arsb enzyme activity; the mouse donor annotation is an IMP (PMID:26234751 per QuickGO). acts_upstream_of_or_within is an appropriate qualifier that does not overclaim a direct developmental function.

Summary: Manual ISS transfer of the specific MF from an experimentally annotated ortholog.

Reason: Higher-quality curator-adjudicated evidence than pure IEA for the core molecular function.

Summary: Duplicate cell-surface annotation via ISO from mammalian orthologs.

Reason: Non-core extra-lysosomal localisation, corroborated by the rat IDA evidence (PMID:19536613).

Summary: Direct experimental demonstration by immunohistochemistry and electron microscopy that ARSA and ARSB localise to the cell surface of sinusoidal endothelial cells, hepatocytes, and Kupffer cells in rat/mammalian liver, colocalising with heparan sulfate proteoglycan.

Reason: Strong IDA evidence for a genuine extra-lysosomal localisation. Non-core because the primary functional compartment is the lysosome, but this is a reproducibly observed second site with likely relevance to extracellular GAG biology and to MPS VI pathophysiology.

Summary: Manual ISS propagation from the human ARSB IMP annotation (PMID:19306108).

Reason: Conserved non-core function of ARSB in the mammalian lineage.

Summary: Duplicate ISO propagation of the same term.

Reason: Same rationale as the ISS/IEA versions.

Summary: Zhang et al. 2014 directly show that silencing Arsb in astrocytes (or ethanol-mediated Arsb inhibition) increases sulfated GAGs, C4S, and neurocan and reduces neurite outgrowth in cocultured hippocampal neurons; recombinant Arsb rescues the ethanol-induced defect. In vivo, ethanol also reduces Arsb activity and elevates sulfated GAG/neurocan in developing rat hippocampus.

Reason: Well-supported IMP annotation for a bona fide non-core, CNS/ developmental role of Arsb mediated via astrocyte GAG/neurocan turnover. Retain but flag as non-core, because the primary Arsb function is lysosomal GAG catabolism.

Summary: Manual ISS propagation of the tissue-specific descendant term.

Reason: Same rationale as the IEA colon epithelial cell migration annotation.

Summary: Duplicate ISO propagation.

Reason: Same rationale.

Summary: Sanghavi & Koenig (1976) measured the ratio of lysosomal arylsulphatase A to arylsulphatase B activity in rat liver under conditions that induce hepatic autophagocytosis (starvation, sham or subtotal hepatectomy, glucagon + starvation). They observed that the A/B activity ratio declines during enhanced autophagocytosis and interpreted this as arylsulphatase A being converted to arylsulphatase B by other lysosomal hydrolases active in autophagic vacuoles. The arylsulphatases are described as targets/substrates of autophagic processing, not as effectors of autophagy. This is the concern raised in geneontology/go-annotation issue 6467 by curator @vanaukenk. Only the abstract is available for this 1976 paper; a full-text review may add information, but the abstract itself does not support a role for Arsb in the autophagy process.

Reason: The cited paper (PMID:8037) describes autophagy-associated changes in arylsulphatase A/B activity ratios (with A converted to B during autophagic proteolysis), not a functional role for Arsb in autophagy itself. This IDA is the source that has been electronically propagated to the human ortholog ARSB (P15848), where the propagated autophagy annotation is already flagged for removal (see genes/human/ARSB/ARSB-ai-review.yaml). Marking as over-annotated (rather than REMOVE) preserves the original curator judgment while flagging the annotation for community adjudication under geneontology/go-annotation issue 6467.

Summary: Ferland et al. 1990 measured lysosomal enzyme activities in hepatocytes, Kupffer, and endothelial cells of rats aged 3.5, 12, and 24 months under ad libitum vs dietary-restricted feeding. Dietary restriction elevated Arsb (and beta-galactosidase, cathepsin D) activity in Kupffer/endothelial cells. This is an expression/activity change of Arsb in response to dietary state; it does not show that Arsb is part of a nutrient-response signalling or effector pathway.

Reason: The observation that Arsb activity changes with dietary restriction is a phenotypic/expression response, not evidence that Arsb is a component of a response to nutrient biological process. The primary function of Arsb is lysosomal GAG catabolism; this IDA should be flagged rather than accepted as a core involvement.

Summary: Thompson & Daniel 1987 isolated rat hepatic ascorbic acid-2-sulfatases and biochemically demonstrated that arylsulfatase B is responsible for the cationic ascorbic acid-2-sulfatase activity, supporting the sulfuric ester hydrolase activity assignment.

Reason: High-quality biochemical IDA support. Unlike the IBA/IEA rows for the same term, this row is at the right breadth, because the assayed substrate was ascorbic acid-2-sulfate rather than an N-acetylgalactosamine-4-sulfate; narrowing it to GO:0003943 would assert a reaction the paper did not measure, and no specific GO term exists for ascorbate-2-sulfate hydrolysis. Policy applied across this re-review batch is that an uninformative broad parent of a specific activity or process the gene already carries is MODIFIED to that specific term; experimental rows stay at the curator's breadth unless the cited assay itself identifies the specific substrate.

Summary: O'Fagain et al. 1983 is a biophysical/enzyme-kinetics study of rat liver arylsulphatases showing pH dependence of activity with pK values 4.4-4.5 and 5.7-5.8, and proposing a general acid-base- catalysed mechanism. The paper measures how enzyme activity depends on assay pH (a property of the catalytic mechanism), not a biological response to pH process by the organism/cell.

Reason: This annotation misinterprets an enzyme-kinetics observation (pH-dependent catalytic rate) as involvement in the biological process response to pH. Almost every enzyme has some pH dependence; that does not make it part of a cellular pH-response pathway. This IDA is a demonstrable mis-classification of the evidence and should be removed.

Summary: Zachariah & Moudgal 1977 show that a single subcutaneous injection of estradiol into ovariectomised rats increases cervical arylsulphatase A and B specific activity, and that cycloheximide blocks this rise, suggesting regulation at the level of protein biosynthesis. This is estrogen-induced expression of Arsb in a specific tissue (cervix), not a core Arsb function.

Reason: The IDA evidence is genuine (estrogen upregulates Arsb expression in cervical tissue), but this is regulation of Arsb by estrogen rather than a general Arsb involvement in estrogen response signalling. Retain as non-core to preserve the tissue-specific hormonal-regulation observation without overclaiming it as a core function.

Summary: Vinay & Sood 1991 show that methyl mercuric chloride dose-dependently inhibits CNS arylsulfatase activity in rats and that thiol antagonists (NAHT, GSH) fail to restore it. The paper demonstrates methylmercury toxicology (Arsb inhibition), not a role for Arsb in a response to methylmercury biological process.

Reason: The evidence shows that methylmercury inhibits Arsb (a chemical toxicology observation), not that Arsb participates in a cellular response-to-methylmercury pathway. The GO term is mis-assigned: the paper measures Arsb sensitivity to a toxin, which is a property of the enzyme, not evidence that Arsb is a component of a defensive or response biological process.

Summary: Kunieda et al. 1995 cloned rat Arsb cDNA, identified the 507insC frameshift mutation causing MPS VI in the MPR rat colony, and confirmed rat Arsb as the arylsulfatase B ortholog of human ARSB (~80/85% nt/aa identity).

Reason: Foundational reference for rat Arsb identity as an arylsulfatase. Traceable author statement based on molecular characterisation.

Summary: ISO propagation of the arylsulfatase MF from human/mouse.

Reason: Rat liver lysosomal arylsulphatase B was resolved and measured with the aryl sulfate p-nitrocatechol sulphate (PMID:8037), consistent with the mouse donor annotation (IDA PMID:7470017 per QuickGO) and with the rat cloning data (PMID:8575749).

Summary: Proposed new biological process. Arsb removes the 4-sulfate from N-acetylgalactosamine 4-sulfate residues of dermatan sulfate and chondroitin sulfate in the lysosome, one of the sequential enzymatic steps that degrade these glycosaminoglycan chains. The gene already carries the chondroitin sulfate and dermatan sulfate proteoglycan catabolic process terms, but GO:0006027 is not an ancestor of those terms, so this adds the glycosaminoglycan-level process rather than duplicating them.

Reason: Participation test: Arsb itself catalyzes a step in GAG degradation (desulfation of GalNAc-4-sulfate), so it does part of the work of the process; it is not merely required for it. Comparator check (QuickGO, human/mouse/rat): other lysosomal GAG-degrading enzymes acting on the same or related chains, including GUSB, IDUA, IDS and SGSH, carry GO:0006027, so the term fits the convention for this enzyme class.