GNS (N-acetylglucosamine-6-sulfatase; EC 3.1.6.14, also called glucosamine-6-sulfatase/G6S) is a lysosomal exo-sulfatase that hydrolytically removes the 6-O-sulfate group from terminal N-acetyl-D-glucosamine-6-sulfate residues during the stepwise exolytic degradation of the glycosaminoglycans heparan sulfate and keratan sulfate. Like other members of the sulfatase family, it depends on a catalytic C-alpha-formylglycine residue generated from an active-site cysteine by the formylglycine-generating enzyme SUMF1, and it binds a catalytic Ca2+ ion. The mature enzyme is synthesized as a glycosylated precursor with a cleavable signal peptide and acts in the lysosomal lumen at acidic pH. Loss of GNS activity causes mucopolysaccharidosis type IIID (Sanfilippo syndrome D), an autosomal-recessive lysosomal storage disorder marked by heparan sulfate accumulation and progressive central nervous system degeneration.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005764 lysosome | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (IBA) annotation placing the active enzyme in the lysosome. This matches the UniProt subcellular location and the well-established role of GNS as an acid hydrolase acting in lysosomal glycosaminoglycan degradation. Core localization; accept. Reason: GNS is a lysosomal sulfatase; UniProt records subcellular location Lysosome and its function is defined by lysosomal degradation of heparan/keratan sulfate. Supporting Evidence: file:human/GNS/GNS-uniprot.txt SUBCELLULAR LOCATION: Lysosome. PMID:1463457 Glucosamine-6-sulphatase is an exo-hydrolase required for the lysosomal degradation of heparan sulphate and keratan sulphate. |
| GO:0030200 heparan sulfate proteoglycan catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (IBA) annotation to heparan sulfate catabolism, consistent with the enzyme's defined role in the stepwise exolytic degradation of heparan sulfate. Core biological process; accept. Reason: GNS removes the 6-sulfate from terminal GlcNAc-6-sulfate residues, a required step in lysosomal heparan sulfate degradation; its deficiency causes lysosomal storage of heparan sulfate (MPS IIID). Supporting Evidence: PMID:1463457 Deficiency of glucosamine-6-sulphatase activity leads to the lysosomal storage of the glycosaminoglycan, heparan sulphate |
| GO:0008449 N-acetylglucosamine-6-sulfatase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic (IBA) annotation to the exact molecular function of GNS. This is the core catalytic activity, independently supported by direct enzymology; accept. Reason: The GO term definition (hydrolysis of the 6-sulfate group of GlcNAc-6-sulfate units of heparan and keratan sulfate) matches the experimentally established activity (EC 3.1.6.14). Supporting Evidence: file:human/GNS/GNS-uniprot.txt Hydrolyzes 6-sulfate groups in N-acetyl-d-glucosaminide units |
| GO:0005764 lysosome | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic annotation (combined IEA methods / UniProt-SubCell) to lysosome, agreeing with the curated UniProt subcellular location. Accept. Reason: Redundant with the IBA lysosome annotation and with UniProt's curated Lysosome location; the IEA mapping is correct. Supporting Evidence: file:human/GNS/GNS-uniprot.txt SUBCELLULAR LOCATION: Lysosome. |
| GO:0008449 N-acetylglucosamine-6-sulfatase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic annotation to the specific sulfatase activity, transferred from InterPro/EC (EC:3.1.6.14) and orthologs. Correct and matches the experimentally verified activity; accept. Reason: The InterPro family (IPR012251, GlcNAc_6-SO4ase) and EC 3.1.6.14 map precisely to GO:0008449; consistent with direct enzymology. Supporting Evidence: PMID:1463457 We have isolated human cDNA clones and derived amino acid sequence coding for the entire glucosamine-6-sulphatase protein |
| GO:0030203 glycosaminoglycan metabolic process | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro2GO electronic annotation to the broad glycosaminoglycan metabolic parent. Not wrong, but less informative than the specific heparan/keratan sulfate catabolic terms already annotated. Keep as non-core. Reason: This is a high-level metabolic parent; the specific catabolic processes (heparan sulfate, keratan sulfate, glycosaminoglycan catabolic process) capture the function more precisely and are retained as core. Supporting Evidence: PMID:3689315 Forms A and B both desulphate substrates derived from keratan sulphate and heparin. |
| GO:0005515 protein binding | IPI PMID:17474147 Systematic identification of SH3 domain-mediated human prote... | MARK AS OVER ANNOTATED | Summary: IPI annotation to bare "protein binding" from a high-throughput SH3-domain peptide-array screen (NCK1 SH3 domain, UniProtKB:P16333). "Protein binding" is uninformative about GNS's molecular function, and the interaction derives from a proteome-wide peptide-array method rather than a validated functional complex. Retained but flagged as over-annotation. Reason: Per curation guidelines, bare "protein binding" IPIs add no functional information; this one comes from a systematic SH3 peptide-array screen. There is no evidence that NCK1 binding is part of GNS's biological function, so it is marked as over-annotated rather than removed. Supporting Evidence: PMID:17474147 A group of 12 Src homology (SH) 3 domains from eight human proteins (Swiss-Prot ID: SRC, PLCG1, P85A, NCK1, GRB2, FYN, CRK) were used to screen a peptide target array |
| GO:0005539 glycosaminoglycan binding | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Electronic annotation (Ensembl ortholog transfer) to glycosaminoglycan binding. GNS acts on GAG substrates (heparan/keratan sulfate), so substrate binding is plausible, but as a binding term it is subsumed by the catalytic activity and does not add core functional information. Keep as non-core. Reason: Binding of the GAG substrate is inherent to the enzyme's catalytic activity (GO:0008449); the standalone binding term is not independently informative of GNS's core function. Supporting Evidence: PMID:3689315 Aglycone structures that influence substrate binding and/or enzyme activity |
| GO:0030200 heparan sulfate proteoglycan catabolic process | IEA GO_REF:0000120 | ACCEPT | Summary: Electronic annotation redundant with the IBA and IDA annotations to heparan sulfate catabolism. Correct core biological process; accept. Reason: Consistent with the experimentally supported role of GNS in lysosomal heparan sulfate degradation. Supporting Evidence: PMID:1463457 an exo-hydrolase required for the lysosomal degradation of heparan sulphate and keratan sulphate |
| GO:0042340 keratan sulfate proteoglycan catabolic process | IEA GO_REF:0000107 | ACCEPT | Summary: Electronic annotation (Ensembl ortholog transfer) to keratan sulfate catabolism. GNS also desulfates keratan-sulfate-derived substrates, so this process is a genuine part of its function. Accept as core. Reason: UniProt FUNCTION and EC 3.1.6.14 both name keratan sulfate as a substrate, and direct enzymology shows desulfation of keratan-sulfate-derived substrates. Supporting Evidence: file:human/GNS/GNS-uniprot.txt of heparin sulfate and keratan sulfate. PMID:3689315 Forms A and B both desulphate substrates derived from keratan sulphate and heparin. |
| GO:0043199 sulfate binding | IEA GO_REF:0000107 | KEEP AS NON CORE | Summary: Electronic annotation (Ensembl ortholog transfer) to sulfate binding. Sulfate is the product moiety released by GNS and sulfate/phosphate ions are potent product inhibitors, so sulfate contact is expected, but the term is not independently informative of the core function. Keep as non-core. Reason: Sulfate interaction is a facet of the catalytic mechanism (product/inhibitor binding) rather than a distinct core molecular function; subsumed by GO:0008449. Supporting Evidence: PMID:3689315 Sulphate and phosphate ions are potent inhibitors of enzyme activity. |
| GO:0008449 N-acetylglucosamine-6-sulfatase activity | TAS Reactome:R-HSA-2263495 | ACCEPT | Summary: TAS annotation (Reactome) to the specific sulfatase activity, in the context of the keratan sulfate degradation / MPS IIID pathway. Core molecular function; accept. Reason: Reactome represents the curated pathway role of GNS cleaving sulfate from GlcNAc-6-sulfate units; consistent with all other lines of evidence. Supporting Evidence: PMID:3689315 Enzyme activity is highly specific towards glucosamine 6-sulphate or glucose 6-sulphate residues. |
| GO:0008449 N-acetylglucosamine-6-sulfatase activity | EXP PMID:1463457 A cDNA clone for human glucosamine-6-sulphatase reveals diff... | ACCEPT | Summary: Experimental (EXP) annotation from the cloning/characterization paper that established the catalytic activity (EC 3.1.6.14) and the full-length human sequence. This is the primary experimental support for the core molecular function; accept. Reason: Direct demonstration of catalytic activity and derivation of the entire glucosamine-6- sulphatase coding sequence; the definitive experimental evidence for GO:0008449. Supporting Evidence: PMID:1463457 Glucosamine-6-sulphatase is an exo-hydrolase required for the lysosomal degradation of heparan sulphate and keratan sulphate. |
| GO:0008449 N-acetylglucosamine-6-sulfatase activity | IDA PMID:15595925 Purification of a 75 kDa protein from the organelle matrix o... | ACCEPT | Summary: IDA annotation from purification of the enzyme from human neutrophil granules and its identification as N-acetylglucosamine-6-sulphatase (EC 3.1.6.14) with confirmed activity toward N-acetylglucosamine-6-sulphate. Direct experimental support for the core activity; accept. Reason: The purified 75 kDa neutrophil protein was identified by MS and its identity confirmed by enzymatic activity toward the GlcNAc-6-sulphate substrate, directly demonstrating GO:0008449. Supporting Evidence: PMID:15595925 identified the protein to be N-acetylglucosamine-6-sulphatase (EC 3.1.6.14). The identity of the protein was confirmed by demostrating enzymatic activity towards the substrate N-acetylglucosamine 6-sulphate. |
| GO:0030200 heparan sulfate proteoglycan catabolic process | IDA PMID:15595925 Purification of a 75 kDa protein from the organelle matrix o... | ACCEPT | Summary: IDA annotation to heparan sulfate catabolism from the neutrophil-enzyme study, which showed O-desulphation activity toward heparan-sulphate-derived saccharides. Consistent with the core catabolic role; accept. Reason: The purified enzyme desulfated heparan-sulphate-derived saccharides, directly linking its activity to heparan sulfate degradation. Supporting Evidence: PMID:15595925 The enzyme also showed O-desulphation activity towards heparan sulphate-derived saccharides. |
| GO:0042582 azurophil granule | IDA PMID:15595925 Purification of a 75 kDa protein from the organelle matrix o... | KEEP AS NON CORE | Summary: IDA annotation locating GNS to azurophil (primary) granules of human neutrophils, based on subcellular fractionation showing activity mainly in primary-granule fractions. This is a genuine, experimentally supported neutrophil-specific location, but secondary to the core lysosomal compartment where GNS performs GAG catabolism. Keep as non-core. Reason: Azurophil (primary) granules are a specialized neutrophil location; the annotation is valid but represents a cell-type-specific compartment rather than the canonical lysosomal site of GNS's core catabolic function. Supporting Evidence: PMID:15595925 Subcellular fractionation of neutrophil organelles showed the presence of enzymatic activity mainly in the same fractions as primary granules. |
| GO:0005576 extracellular region | TAS Reactome:R-HSA-6798751 | KEEP AS NON CORE | Summary: TAS annotation (Reactome neutrophil-degranulation pathway) placing GNS in the extracellular region upon exocytosis of azurophil granule contents. Consistent with the biochemical observation that GNS is released from neutrophils; a secondary, context-dependent location. Keep as non-core. Reason: Reflects release of granule contents during neutrophil degranulation; not the compartment of GNS's core lysosomal catabolic function. Supporting Evidence: PMID:15595925 PMA treatment of the neutrophils induced release of the enzyme, indicating its matrix protein nature. |
| GO:0005576 extracellular region | TAS Reactome:R-HSA-6800434 | KEEP AS NON CORE | Summary: TAS annotation (Reactome ficolin-rich granule exocytosis pathway) placing GNS in the extracellular region upon degranulation. Same rationale as the other extracellular-region annotation; secondary location. Keep as non-core. Reason: Context-dependent extracellular localization following granule exocytosis; not the core lysosomal compartment. Supporting Evidence: PMID:15595925 PMA treatment of the neutrophils induced release of the enzyme, indicating its matrix protein nature. |
| GO:0035578 azurophil granule lumen | TAS Reactome:R-HSA-6798751 | KEEP AS NON CORE | Summary: TAS annotation (Reactome) to azurophil granule lumen, consistent with the experimental demonstration that GNS is a soluble matrix protein of neutrophil primary granules. Secondary, cell-type-specific location. Keep as non-core. Reason: Corroborated by biochemistry (matrix protein of primary granules) but represents a specialized neutrophil compartment rather than the core lysosomal site. Supporting Evidence: PMID:15595925 indicating its matrix protein nature |
| GO:1904813 ficolin-1-rich granule lumen | TAS Reactome:R-HSA-6800434 | KEEP AS NON CORE | Summary: TAS annotation (Reactome) to ficolin-1-rich granule lumen, from the neutrophil-degranulation curation. A specialized neutrophil granule subtype; secondary location. Keep as non-core. Reason: Neutrophil-granule-subtype location derived from pathway curation; not the core lysosomal compartment for GAG catabolism. Supporting Evidence: PMID:15595925 Subcellular fractionation of neutrophil organelles showed the presence of enzymatic activity mainly in the same fractions as primary granules. |
| GO:0043202 lysosomal lumen | TAS Reactome:R-HSA-2263495 | ACCEPT | Summary: TAS annotation (Reactome) to the lysosomal lumen, the compartment where GNS performs GlcNAc-6- sulfate desulfation during GAG catabolism. Core localization; accept. Reason: GNS is a soluble luminal lysosomal hydrolase; the lysosomal lumen is its functional compartment. Supporting Evidence: file:human/GNS/GNS-uniprot.txt SUBCELLULAR LOCATION: Lysosome. |
| GO:0070062 extracellular exosome | HDA PMID:23533145 In-depth proteomic analyses of exosomes isolated from expres... | KEEP AS NON CORE | Summary: High-throughput (HDA) detection of GNS in exosomes purified from expressed prostatic secretions in urine, from a shotgun proteomics survey of ~900 proteins. This reflects presence in a secreted vesicle fraction rather than a core functional location. Keep as non-core. Reason: Large-scale proteomic detection in an exosome preparation; consistent with GNS being a soluble, secretable hydrolase but not indicative of its core catabolic site. Supporting Evidence: PMID:23533145 In pooled EPS-urine exosome samples, ~900 proteins were detected. |
| GO:0043202 lysosomal lumen | TAS Reactome:R-HSA-1638032 | ACCEPT | Summary: TAS annotation (Reactome keratan sulfate degradation reaction) to lysosomal lumen. Redundant with the other lysosomal-lumen annotation and consistent with GNS's core compartment; accept. Reason: GNS acts as a soluble luminal lysosomal enzyme; lysosomal lumen is the correct core location. Supporting Evidence: file:human/GNS/GNS-uniprot.txt SUBCELLULAR LOCATION: Lysosome. |
| GO:0008484 sulfuric ester hydrolase activity | IDA PMID:15962010 Sulphatase activities are regulated by the interaction of su... | MODIFY | Summary: IDA annotation to the broad "sulfuric ester hydrolase activity" parent, from a study of SUMF1/SUMF2 regulation in which GNS was among the sulphatases assayed. GNS's specific activity is N-acetylglucosamine-6-sulfatase (GO:0008449), a child of this term, so the annotation should be made more specific. Reason: GO:0008484 is the sulfatase-family parent; the specific, experimentally established activity of GNS is GO:0008449. Replace with the specific term. The SUMF1/SUMF2 study confirms GNS is a formylglycine-dependent sulphatase whose activity is modulated by SUMF1. Proposed replacements: N-acetylglucosamine-6-sulfatase activity Supporting Evidence: PMID:15962010 we transfected Cos7 cells with several sulphatase cDNAs ( ARSA , ARSC , ARSF , IDS , SGSH , GALNS , GNS ) file:human/GNS/GNS-uniprot.txt critical for catalytic activity |
| GO:0006027 glycosaminoglycan catabolic process | TAS PMID:3689315 Human liver N-acetylglucosamine-6-sulphate sulphatase. Catal... | ACCEPT | Summary: TAS annotation to glycosaminoglycan catabolic process, from the detailed catalytic-properties study establishing GNS as a highly specific exo-sulfatase acting on heparin/heparan- and keratan-sulfate-derived substrates. Core biological process (parent of the heparan/keratan catabolic terms); accept. Reason: GNS is an exo-enzyme in the stepwise catabolism of glycosaminoglycans; this parent term is appropriate and directly supported by the enzymology. Supporting Evidence: PMID:3689315 Both forms A and B are exo-enzymes, since activity towards internal sulphate ester bonds was not observed. |
| GO:0008449 N-acetylglucosamine-6-sulfatase activity | TAS PMID:3689315 Human liver N-acetylglucosamine-6-sulphate sulphatase. Catal... | ACCEPT | Summary: TAS annotation to the specific molecular function from the catalytic-properties study, which determined kinetic parameters against physiological-substrate analogues and showed high specificity for glucosamine-6-sulphate residues. Core activity; accept. Reason: Detailed enzymology directly supports GO:0008449: high specificity for GlcNAc-6-sulphate / glucose-6-sulphate residues with catalytic efficiency greatly enhanced on physiological-like substrates. Supporting Evidence: PMID:3689315 Enzyme activity is highly specific towards glucosamine 6-sulphate or glucose 6-sulphate residues. |
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Download this section (compressed HTML)Q: Does GNS have any non-lysosomal physiological role in extracellular glycosaminoglycan remodeling, given its presence and O-desulphation activity in neutrophil primary granules and its release upon degranulation?
Experiment: Structure-guided characterization of the formylglycine-dependent active site (Cys91 -> FGly, Ca2+ coordination) to map how MPS IIID missense variants (e.g. S94I, K340R, G418E) disrupt catalysis or protein stability.
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