id: P34059
gene_symbol: GALNS
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  GALNS (N-acetylgalactosamine-6-sulfatase, also known as galactose-6-sulfate sulfatase,
  GalN6S; EC 3.1.6.4) is a lysosomal sulfatase acting in the stepwise degradation of the
  glycosaminoglycans keratan sulfate and chondroitin-6-sulfate. It hydrolytically removes the
  6-O-sulfate group from terminal N-acetyl-D-galactosamine-6-sulfate residues of chondroitin
  sulfate and from D-galactose-6-sulfate residues of keratan sulfate. Like all members of the
  sulfatase family, GALNS requires post-translational conversion of an active-site cysteine
  (Cys79) to Cα-formylglycine (3-oxoalanine) by the formylglycine-generating enzyme SUMF1; this
  modified residue, together with a bound Ca2+ ion, forms the catalytic nucleophile. GALNS is a
  homodimeric N-glycosylated glycoprotein that localises to the lysosome (lysosomal lumen), and,
  as a secreted lysosomal hydrolase, is also detected extracellularly. Deficiency of GALNS causes
  mucopolysaccharidosis type IVA (Morquio A syndrome), an autosomal recessive lysosomal storage
  disease with intracellular accumulation of keratan sulfate and chondroitin-6-sulfate, presenting
  with short stature, skeletal dysplasia, and corneal clouding.
references:
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:15962010
  title: Sulphatase activities are regulated by the interaction of sulphatase-modifying
    factor 1 with SUMF2.
  findings:
  - statement: >-
      The formylglycine (FGly) modification of an active-site cysteine, generated by SUMF1 within
      the ER, is required for the catalytic activity of the sulphatases (including GALNS); SUMF2
      modulates SUMF1 activity.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PMC full text available. Establishes the SUMF1/formylglycine dependence shared by GALNS; GALNS
      is among the sulphatases assayed. Supports the general sulfatase-maturation requirement rather
      than a GALNS-specific function.
- id: PMID:18285341
  title: Distinct effects of N-acetylgalactosamine-4-sulfatase and galactose-6-sulfatase
    expression on chondroitin sulfates.
  findings:
  - statement: >-
      Galactose-6-sulfatase (GALNS) hydrolyses sulfate groups of chondroitin sulfate; modulating
      GALNS expression (overexpression vs siRNA silencing) inversely changes cellular chondroitin
      sulfate content, demonstrating a role in chondroitin sulfate catabolism.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache, but the abstract explicitly links GALNS expression to cellular chondroitin
      sulfate content in MCF-7 cells; supports the chondroitin sulfate catabolic-process annotation.
- id: PMID:22940367
  title: The structure of human GALNS reveals the molecular basis for mucopolysaccharidosis
    IV A.
  findings:
  - statement: >-
      Crystal structure of human GALNS (EC 3.1.6.4); the enzyme removes 6-sulfate groups from terminal
      N-acetylgalactosamine-6-sulfate (chondroitin-6-sulfate) and galactose-6-sulfate (keratan sulfate).
      Formylglycine-generating enzyme converts Cys79 to a formylglycine nucleophile; the enzyme is a
      Ca2+-binding homodimer.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      PMC full text. Definitive structural and enzymological characterisation of human GALNS; the
      primary support for the core molecular function, formylglycine mechanism, and homodimeric Ca2+
      cofactor biology.
- id: PMID:23533145
  title: In-depth proteomic analyses of exosomes isolated from expressed prostatic
    secretions in urine.
  findings:
  - statement: >-
      Shotgun proteomics of exosomes from expressed prostatic secretions in urine detected ~900 proteins,
      among them GALNS, consistent with its presence in the secreted/extracellular-exosome fraction.
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      High-throughput proteomic detection in prostatic-secretion exosomes; supports extracellular-exosome
      localisation only, not a core function.
- id: PMID:30760748
  title: Expression, activity and localization of lysosomal sulfatases in Chronic
    Obstructive Pulmonary Disease.
  findings:
  - statement: >-
      Immunostaining of cultured lung fibroblasts shows GALNS in a lysosomal localisation in both ever
      smokers and COPD patients, confirming lysosomal localisation.
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      PMC full text. Direct immunolocalisation evidence for lysosomal localisation of GALNS; source of
      the IDA lysosome annotation.
- id: PMID:8325655
  title: 'Mucopolysaccharidosis IV A: assignment of the human N-acetylgalactosamine-6-sulfate
    sulfatase (GALNS) gene to chromosome 16q24.'
  findings:
  - statement: >-
      Chromosome-mapping study assigning the human N-acetylgalactosamine-6-sulfate sulfatase (GALNS;
      EC 3.1.6.4) gene to chromosome 16q24; the paper does not assay a 4-sulfatase activity.
  reference_review:
    relevance: LOW
    correctness: MISCITED
    review_notes: >-
      This is a gene-mapping (FISH/chromosome-assignment) abstract for GALNS. It was cited (TAS) to
      support GO:0003943 N-acetylgalactosamine-4-sulfatase activity, but GALNS is a 6-sulfatase
      (EC 3.1.6.4); the 4-sulfatase is ARSB. The paper does not support a 4-sulfatase activity.
- id: PMID:820716
  title: N-acetylgalactosamine-6-sulfate sulfatase in man. Absence of the enzyme in
    Morquio disease.
  findings:
  - statement: >-
      Original demonstration of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) activity in man and
      its absence in Morquio disease; source of the EC 3.1.6.4 catalytic-activity assignment in UniProt.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      UniProt cites this (ECO:0000269|PubMed:820716) for FUNCTION and CATALYTIC ACTIVITY. Not separately
      annotated in GOA but underpins the core molecular function.
- id: Reactome:R-HSA-1630304
  title: GALNS oligomer hydrolyses sulfate from Gal6S in keratan sulfate
  findings: []
- id: Reactome:R-HSA-2263490
  title: Defective GALNS does not hydrolyse sulfate from Gal6S in keratan sulfate
  findings: []
- id: Reactome:R-HSA-6798751
  title: Exocytosis of azurophil granule lumen proteins
  findings: []
- id: file:human/GALNS/GALNS-uniprot.txt
  title: UniProtKB P34059 (GALNS_HUMAN) curated record
  findings:
  - statement: >-
      FUNCTION: lysosomal enzyme that hydrolyzes sulfate groups from the glycosaminoglycans keratan
      sulfate and chondroitin-6-sulfate; SUBCELLULAR LOCATION lysosome; homodimer; formylglycine
      (3-oxoalanine) modification of Cys79 critical for activity; deficiency causes MPS4A (Morquio A).
existing_annotations:
- term:
    id: GO:0004065
    label: arylsulfatase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      Family-level (arylsulfatase) molecular function assigned by phylogenetic inference across the
      sulfatase family. GALNS is a bona fide sulfatase, so this term is correct but broad relative to
      its specific N-acetylgalactosamine-6-sulfatase activity.
    action: ACCEPT
    reason: >-
      The IBA sulfatase-family term is biologically correct: GALNS catalyses sulfate-ester hydrolysis
      and belongs to the sulfatase family. It is more general than the specific 6-sulfatase activity
      (GO:0043890, also annotated), and it is standard to retain the broader family MF alongside the
      specific one. Kept, though the specific GO:0043890 term better represents the core function.
    supported_by:
    - reference_id: PMID:22940367
      supporting_text: >-
        In sulfatases, highly conserved catalytic machinery couples with diverse active site geometry,
        leading to cleavage of a wide variety of substrates.
    - reference_id: file:human/GALNS/GALNS-uniprot.txt
      supporting_text: Belongs to the sulfatase family.
- term:
    id: GO:0005764
    label: lysosome
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: >-
      Electronic localisation to the lysosome, consistent with UniProt SUBCELLULAR LOCATION and with
      direct immunolocalisation (GO:0005764 IDA from PMID:30760748).
    action: ACCEPT
    reason: >-
      GALNS is a well-established lysosomal hydrolase; the IEA lysosome call agrees with experimental
      IDA evidence and UniProt curation, so it is retained as a correct core localisation.
    supported_by:
    - reference_id: file:human/GALNS/GALNS-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome'
    - reference_id: PMID:30760748
      supporting_text: GALNS indeed showed a lysosomal localization in both ever smokers and COPD patients.
- term:
    id: GO:0043890
    label: N-acetylgalactosamine-6-sulfatase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >-
      Specific molecular function: removal of the 6-O-sulfate from N-acetyl-D-galactosamine-6-sulfate
      (chondroitin-6-sulfate) and D-galactose-6-sulfate (keratan sulfate). This is the correct core MF
      for GALNS (EC 3.1.6.4), inferred here electronically from InterPro/EC mapping.
    action: ACCEPT
    reason: >-
      The GO:0043890 definition matches the experimentally established catalytic activity of GALNS
      exactly, and the same term is independently supported by EXP and IDA annotations. This is the
      core molecular function.
    supported_by:
    - reference_id: PMID:22940367
      supporting_text: >-
        removes sulfate groups from a terminal N-acetylgalactosamine-6-sulfate (or galactose-6-sulfate)
        in mucopolysaccharides such as keratan sulfate and chondroitin-6-sulfate
    - reference_id: file:human/GALNS/GALNS-uniprot.txt
      supporting_text: Lysosomal enzyme that hydrolyzes sulfate groups from
- term:
    id: GO:0043890
    label: N-acetylgalactosamine-6-sulfatase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2263490
  qualifier: enables
  review:
    summary: >-
      Reactome-asserted core molecular function (6-sulfatase acting on Gal6S/GalNAc6S in keratan sulfate
      and chondroitin sulfate).
    action: ACCEPT
    reason: >-
      Reactome models GALNS hydrolysing sulfate from galactose-6-sulfate in keratan sulfate and from
      N-acetylgalactosamine-6-sulfate in chondroitin sulfate; this is the correct core MF and duplicates
      the experimentally supported GO:0043890 annotation.
    supported_by:
    - reference_id: Reactome:R-HSA-1630304
      supporting_text: hydrolyses sulfate from galactose 6-sulfate units of keratan sulfate
    - reference_id: PMID:22940367
      supporting_text: >-
        In the lysosome, GALNS removes sulfate groups from 6-sulfated galactosides and 6-sulfated
        N-acetylgalactosaminides in keratan sulfate and chondroitin-6-sulfate
- term:
    id: GO:0005764
    label: lysosome
  evidence_type: IDA
  original_reference_id: PMID:30760748
  qualifier: located_in
  review:
    summary: >-
      Direct immunolocalisation of GALNS to the lysosome in cultured human lung fibroblasts.
    action: ACCEPT
    reason: >-
      Experimental (IDA) evidence: co-staining with lysosomal markers showed GALNS in a lysosomal
      localisation. This confirms the core subcellular location.
    supported_by:
    - reference_id: PMID:30760748
      supporting_text: GALNS indeed showed a lysosomal localization in both ever smokers and COPD patients.
- term:
    id: GO:0043890
    label: N-acetylgalactosamine-6-sulfatase activity
  evidence_type: EXP
  original_reference_id: PMID:22940367
  qualifier: enables
  review:
    summary: >-
      Experimental characterisation (structure and enzyme kinetics) of human GALNS as an
      N-acetylgalactosamine-6-sulfatase acting on keratan sulfate and chondroitin-6-sulfate.
    action: ACCEPT
    reason: >-
      Direct experimental support for the core molecular function: the crystallographic and kinetic
      study defines GALNS as removing 6-sulfate groups from the terminal sugars of keratan sulfate and
      chondroitin-6-sulfate, with a Ca2+/formylglycine active site.
    supported_by:
    - reference_id: PMID:22940367
      supporting_text: >-
        In the lysosome, GALNS removes sulfate groups from 6-sulfated galactosides and 6-sulfated
        N-acetylgalactosaminides in keratan sulfate and chondroitin-6-sulfate
- term:
    id: GO:0030207
    label: chondroitin sulfate proteoglycan catabolic process
  evidence_type: IDA
  original_reference_id: PMID:18285341
  qualifier: involved_in
  review:
    summary: >-
      GALNS contributes to catabolism of chondroitin sulfate: modulating GALNS expression inversely
      changes cellular chondroitin sulfate content.
    action: ACCEPT
    reason: >-
      Experimental (IDA) evidence in MCF-7 cells shows that overexpression of GALNS lowers, and silencing
      raises, chondroitin sulfate content, supporting a direct role in chondroitin-6-sulfate catabolism.
      This is a genuine core biological process (the chondroitin side of GALNS's GAG-degradation role).
    supported_by:
    - reference_id: PMID:18285341
      supporting_text: galactose-6-sulfatase (GALNS) hydrolyze sulfate groups of CS
    - reference_id: PMID:18285341
      supporting_text: >-
        modification of expression of the lysosomal sulfatases ASB and GALNS regulates
- term:
    id: GO:0043890
    label: N-acetylgalactosamine-6-sulfatase activity
  evidence_type: IDA
  original_reference_id: PMID:18285341
  qualifier: enables
  review:
    summary: >-
      Direct-assay support for the core 6-sulfatase molecular function of GALNS.
    action: ACCEPT
    reason: >-
      IDA annotation to the correct specific molecular function; GALNS is characterised here as
      galactose-6-sulfatase that hydrolyses sulfate groups of chondroitin sulfate. Duplicates the core
      MF supported by other lines of evidence.
    supported_by:
    - reference_id: PMID:18285341
      supporting_text: galactose-6-sulfatase (GALNS) hydrolyze sulfate groups of CS
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6798751
  qualifier: located_in
  review:
    summary: >-
      Extracellular localisation asserted via Reactome neutrophil-degranulation / azurophil-granule
      exocytosis pathway. A secreted-fraction localisation, not the primary site of GALNS action.
    action: KEEP_AS_NON_CORE
    reason: >-
      As a lysosomal hydrolase, GALNS can be exocytosed and detected extracellularly (e.g. via neutrophil
      degranulation). The localisation is real but peripheral; the core site of action is the lysosome.
    supported_by:
    - reference_id: Reactome:R-HSA-6798751
      supporting_text: Azurophil granules undergo limited exocytosis in response to stimulation
- term:
    id: GO:0035578
    label: azurophil granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6798751
  qualifier: located_in
  review:
    summary: >-
      Localisation to the azurophil (primary) granule lumen of neutrophils, asserted via the Reactome
      neutrophil-degranulation pathway.
    action: KEEP_AS_NON_CORE
    reason: >-
      Azurophil granules are lysosome-related organelles of neutrophils; GALNS presence there reflects
      its lysosomal-hydrolase nature and the degranulation pathway, but this is not the core localisation.
    supported_by:
    - reference_id: Reactome:R-HSA-6798751
      supporting_text: Azurophil granules undergo limited exocytosis in response to stimulation
- term:
    id: GO:0043202
    label: lysosomal lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2263490
  qualifier: located_in
  review:
    summary: >-
      Localisation to the lysosomal lumen, the precise compartment where GALNS acts on keratan sulfate
      and chondroitin-6-sulfate.
    action: ACCEPT
    reason: >-
      Lysosomal lumen is the specific site of GALNS activity as a soluble lysosomal hydrolase; consistent
      with the lysosome IDA/IEA annotations and UniProt curation.
    supported_by:
    - reference_id: Reactome:R-HSA-1630304
      supporting_text: hydrolyses sulfate from galactose 6-sulfate units of keratan sulfate
    - reference_id: file:human/GALNS/GALNS-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome'
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: HDA
  original_reference_id: PMID:23533145
  qualifier: located_in
  review:
    summary: >-
      High-throughput proteomic detection of GALNS in exosomes from expressed prostatic secretions in
      urine. A localisation byproduct of secreted/exosomal trafficking, not a core function.
    action: KEEP_AS_NON_CORE
    reason: >-
      GALNS was among ~900 proteins detected by shotgun proteomics of prostatic-secretion exosomes. This
      supports extracellular-exosome localisation but is peripheral to the enzyme's lysosomal core role.
    supported_by:
    - reference_id: PMID:23533145
      supporting_text: exosome preparations were characterized by a shotgun proteomics procedure
- term:
    id: GO:0043202
    label: lysosomal lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1630304
  qualifier: located_in
  review:
    summary: >-
      Lysosomal-lumen localisation asserted by Reactome for the GALNS keratan-sulfate desulfation
      reaction; the precise site of GALNS catalysis.
    action: ACCEPT
    reason: >-
      Duplicate of the lysosomal-lumen localisation supported by Reactome and UniProt; correct core
      compartment for this soluble lysosomal sulfatase.
    supported_by:
    - reference_id: Reactome:R-HSA-1630304
      supporting_text: hydrolyses sulfate from galactose 6-sulfate units of keratan sulfate
    - reference_id: file:human/GALNS/GALNS-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome'
- term:
    id: GO:0008484
    label: sulfuric ester hydrolase activity
  evidence_type: IDA
  original_reference_id: PMID:15962010
  qualifier: enables
  review:
    summary: >-
      Parent-level molecular function (sulfuric ester hydrolase). GALNS activity was measured in the
      SUMF1/SUMF2 study, but the specific GO:0043890 (6-sulfatase) term is the informative descendant.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      GO:0008484 is a broad ancestor of the specific N-acetylgalactosamine-6-sulfatase activity already
      annotated. GALNS activity was assayed among several sulfatases whose maturation depends on SUMF1;
      the general term adds little beyond the specific GO:0043890 term and is an over-annotation of
      specificity. Not wrong, but subsumed by the core MF.
    supported_by:
    - reference_id: PMID:15962010
      supporting_text: This modification is necessary for the catalytic activities of the sulphatases
    - reference_id: PMID:15962010
      supporting_text: we transfected Cos7 cells with several sulphatase cDNAs
- term:
    id: GO:0003943
    label: N-acetylgalactosamine-4-sulfatase activity
  evidence_type: TAS
  original_reference_id: PMID:8325655
  qualifier: enables
  review:
    summary: >-
      Annotation to N-acetylgalactosamine-4-sulfatase activity, which is the wrong specificity for GALNS.
      GALNS is a 6-sulfatase (EC 3.1.6.4, GO:0043890); the 4-sulfatase (EC 3.1.6.12, GO:0003943) is ARSB.
      The cited reference is a chromosome-mapping abstract that does not assay a 4-sulfatase activity.
    action: MODIFY
    reason: >-
      GO:0003943 catalyses hydrolysis of the 4-sulfate groups of N-acetyl-D-galactosamine-4-sulfate (a
      distinct activity carried out by ARSB), whereas GALNS removes 6-sulfate groups. The original
      reference (PMID:8325655) only assigns the GALNS gene to chromosome 16q24 and does not support a
      4-sulfatase activity. This is a wrong-specificity term (TAS, not experimental IDA); replace with
      the correct 6-sulfatase term GO:0043890.
    proposed_replacement_terms:
    - id: GO:0043890
      label: N-acetylgalactosamine-6-sulfatase activity
    supported_by:
    - reference_id: PMID:8325655
      supporting_text: N-acetylgalactosamine-6-sulfate sulfatase (GALNS; EC 3.1.6.4)
    - reference_id: PMID:22940367
      supporting_text: >-
        In the lysosome, GALNS removes sulfate groups from 6-sulfated galactosides and 6-sulfated
        N-acetylgalactosaminides in keratan sulfate and chondroitin-6-sulfate
- term:
    id: GO:0042340
    label: keratan sulfate proteoglycan catabolic process
  evidence_type: EXP
  original_reference_id: PMID:22940367
  qualifier: involved_in
  review:
    summary: >-
      GALNS removes the 6-O-sulfate from galactose-6-sulfate residues of keratan sulfate, a required step
      in keratan sulfate degradation; deficiency causes lysosomal keratan sulfate accumulation (MPS IVA).
      This keratan-sulfate catabolic role is not currently represented in GOA and is proposed here.
    action: NEW
    reason: >-
      The keratan-sulfate side of GALNS's core biological process is well established (UniProt FUNCTION;
      structural/enzymology study; Reactome "Keratan sulfate degradation") but absent from the GOA
      biological-process set, which only carries the chondroitin-sulfate term GO:0030207. GO:0042340
      (keratan sulfate proteoglycan catabolic process) captures this core role.
    supported_by:
    - reference_id: PMID:22940367
      supporting_text: >-
        removes sulfate groups from a terminal N-acetylgalactosamine-6-sulfate (or galactose-6-sulfate)
        in mucopolysaccharides such as keratan sulfate and chondroitin-6-sulfate
    - reference_id: file:human/GALNS/GALNS-uniprot.txt
      supporting_text: Lysosomal enzyme that hydrolyzes sulfate groups from
core_functions:
- description: >-
    Lysosomal N-acetylgalactosamine-6-sulfatase (galactose-6-sulfate sulfatase, EC 3.1.6.4) that
    hydrolytically removes the 6-O-sulfate group from terminal N-acetyl-D-galactosamine-6-sulfate
    (chondroitin-6-sulfate) and D-galactose-6-sulfate (keratan sulfate) residues, using a
    Ca2+/formylglycine active site, during glycosaminoglycan degradation.
  molecular_function:
    id: GO:0043890
    label: N-acetylgalactosamine-6-sulfatase activity
  directly_involved_in:
  - id: GO:0042340
    label: keratan sulfate proteoglycan catabolic process
  locations:
  - id: GO:0043202
    label: lysosomal lumen
  supported_by:
  - reference_id: PMID:22940367
    supporting_text: >-
      removes sulfate groups from a terminal N-acetylgalactosamine-6-sulfate (or galactose-6-sulfate)
      in mucopolysaccharides such as keratan sulfate and chondroitin-6-sulfate
  - reference_id: file:human/GALNS/GALNS-uniprot.txt
    supporting_text: Lysosomal enzyme that hydrolyzes sulfate groups from
- description: >-
    Same lysosomal 6-sulfatase activity acting on chondroitin-6-sulfate, contributing to chondroitin
    sulfate proteoglycan degradation in the lysosome.
  molecular_function:
    id: GO:0043890
    label: N-acetylgalactosamine-6-sulfatase activity
  directly_involved_in:
  - id: GO:0030207
    label: chondroitin sulfate proteoglycan catabolic process
  locations:
  - id: GO:0043202
    label: lysosomal lumen
  supported_by:
  - reference_id: PMID:18285341
    supporting_text: galactose-6-sulfatase (GALNS) hydrolyze sulfate groups of CS