id: P54802
gene_symbol: NAGLU
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  NAGLU encodes alpha-N-acetylglucosaminidase, a lysosomal exoglycosidase of glycoside
  hydrolase family 89 (CAZy GH89) that catalyses the hydrolysis of terminal non-reducing
  alpha-N-acetyl-D-glucosamine residues in N-acetyl-alpha-D-glucosaminides (EC 3.2.1.50).
  It carries out one step in the ordered, stepwise exolytic degradation of heparan sulfate
  in the lysosome: NAGLU removes the terminal alpha-N-acetylglucosamine residue that is
  exposed after upstream enzymes (SGSH liberates a glucosamine, which HGSNAT then
  N-acetylates). The protein is synthesised as a signal-peptide-bearing precursor,
  N-glycosylated, and processed to mature 82 kDa and 77 kDa lysosomal forms; it functions
  as a monomer or homodimer. Loss of NAGLU activity blocks heparan sulfate catabolism and
  causes mucopolysaccharidosis type IIIB (MPS IIIB, Sanfilippo syndrome B), an autosomal
  recessive lysosomal storage disease dominated by progressive central nervous system
  degeneration. A dominant NAGLU missense variant additionally causes axonal
  Charcot-Marie-Tooth disease type 2V.
existing_annotations:
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      Phylogenetic (IBA) assignment of the core catalytic molecular function of NAGLU,
      alpha-N-acetylglucosaminidase activity, propagated across the GH89 family from
      experimentally characterized orthologs.
    action: ACCEPT
    reason: >-
      This is the defining, experimentally established activity of NAGLU: hydrolysis of
      terminal non-reducing N-acetyl-D-glucosamine residues in N-acetyl-alpha-D-glucosaminides
      (EC 3.2.1.50), consistent with the GO term definition and UniProt. The IBA assignment
      is correct and at the right level of specificity; retained as a core function.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: >-
        Reaction=Hydrolysis of terminal non-reducing N-acetyl-D-glucosamine
        residues in N-acetyl-alpha-D-glucosaminides.; EC=3.2.1.50
    - reference_id: PMID:8650226
      supporting_text: >-
        The Sanfilippo syndrome type B is a lysosomal storage disorder caused by
        deficiency of alpha-N-acetylglucosaminidase
- term:
    id: GO:0005773
    label: vacuole
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: >-
      Phylogenetic (IBA) location annotation to vacuole, the lineage-general parent of the
      lysosome used by GO_Central for this family.
    action: ACCEPT
    reason: >-
      Vacuole (GO:0005773) is the broad, taxon-general term encompassing the lysosome, where
      NAGLU actually acts in animals. It is correct but less specific than the lysosome/lysosomal
      lumen annotations also present; accepted as a valid (if general) location. The specific
      human location is captured by the lysosome and lysosomal lumen annotations.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome.'
- term:
    id: GO:0030202
    label: heparin proteoglycan metabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      Phylogenetic (IBA) biological-process annotation placing NAGLU in heparin proteoglycan
      metabolism.
    action: MODIFY
    reason: >-
      Heparin is a highly sulfated variant of heparan sulfate and NAGLU acts on the shared
      alpha-N-acetylglucosamine linkage, so the annotation is not wrong; however the primary,
      disease-relevant process for NAGLU is the lysosomal catabolism of heparan sulfate.
      Modify to the more accurate and specific heparan sulfate proteoglycan catabolic process,
      which is what the enzyme's deficiency (MPS IIIB) directly impairs.
    proposed_replacement_terms:
    - id: GO:0030200
      label: heparan sulfate proteoglycan catabolic process
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'FUNCTION: Involved in the degradation of heparan sulfate.'
    - reference_id: Reactome:R-HSA-1678742
      supporting_text: >-
        Alpha-N-acetylglucosaminidase (NAGLU) hydrolyses the non-reducing, terminal
        N-acetyl-D-glucosamine residue from heparan sulfate.
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000003
  qualifier: enables
  review:
    summary: >-
      Electronic (IEA) annotation of alpha-N-acetylglucosaminidase activity derived from the
      EC 3.2.1.50 to GO mapping.
    action: ACCEPT
    reason: >-
      The EC-to-GO mapping is exactly correct: NAGLU carries EC 3.2.1.50, and the reaction
      matches the GO term definition. Accepted as a redundant but valid statement of the core
      molecular function.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: >-
        RecName: Full=Alpha-N-acetylglucosaminidase;
        DE            EC=3.2.1.50;
- term:
    id: GO:0005764
    label: lysosome
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: >-
      Electronic (IEA) location annotation to lysosome from the UniProt subcellular-location
      keyword mapping.
    action: ACCEPT
    reason: >-
      NAGLU is a soluble lysosomal hydrolase; the lysosome is its established site of action.
      Correct and core; consistent with the experimental (TAS) lysosome annotation from
      PMID:8650226.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome.'
- term:
    id: GO:0048731
    label: system development
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: involved_in
  review:
    summary: >-
      ARBA machine-learning (IEA) biological-process annotation to the very general term
      system development.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      This general developmental term reflects the disease phenotype (multi-system,
      predominantly neurological deterioration in MPS IIIB) rather than a direct developmental
      role of the enzyme. The observed developmental defects are downstream consequences of
      impaired heparan sulfate catabolism and lysosomal storage, not a molecular developmental
      function of NAGLU. Uninformative at this level and over-annotated.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: >-
        MPS3 is characterized by severe central nervous system degeneration, but only
        mild somatic disease.
- term:
    id: GO:1901135
    label: carbohydrate derivative metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000117
  qualifier: involved_in
  review:
    summary: >-
      ARBA machine-learning (IEA) biological-process annotation to the general term
      carbohydrate derivative metabolic process.
    action: MODIFY
    reason: >-
      NAGLU does act in the metabolism of a carbohydrate derivative (heparan sulfate, an
      N-acetylglucosamine-containing glycosaminoglycan), so the term is not incorrect, but it
      is far too general to be informative. Modify to the specific heparan sulfate proteoglycan
      catabolic process that captures the actual biology.
    proposed_replacement_terms:
    - id: GO:0030200
      label: heparan sulfate proteoglycan catabolic process
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'FUNCTION: Involved in the degradation of heparan sulfate.'
- term:
    id: GO:0030200
    label: heparan sulfate proteoglycan catabolic process
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2024096
  qualifier: involved_in
  review:
    summary: >-
      Reactome (TAS) annotation placing NAGLU in the lysosomal degradation of heparan sulfate
      glycosaminoglycan (HS-GAG degradation pathway).
    action: ACCEPT
    reason: >-
      This is the core biological process for NAGLU. The enzyme performs one exolytic step in
      the ordered lysosomal breakdown of heparan sulfate, removing terminal
      alpha-N-acetylglucosamine residues; its deficiency blocks this catabolic pathway and
      causes MPS IIIB. Accepted as a core function and used as the preferred replacement for
      the more general/heparin-specific process annotations.
    supported_by:
    - reference_id: Reactome:R-HSA-2024096
      supporting_text: >-
        The steps outlined below describe the cleavage of heparan sulfate/heparin from
        heparan sulfate proteoglycans (HSPGs) and its degradation.
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'FUNCTION: Involved in the degradation of heparan sulfate.'
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1678742
  qualifier: enables
  review:
    summary: >-
      Reactome (TAS) annotation of the core catalytic activity in the reaction "NAGLU hydrolyses
      Heparan sulfate chain(4)".
    action: ACCEPT
    reason: >-
      Directly supported: Reactome describes NAGLU hydrolysing the non-reducing terminal
      N-acetyl-D-glucosamine residue from heparan sulfate, which is exactly
      alpha-N-acetylglucosaminidase activity. Redundant with the IBA/IEA MF annotations but
      valid; core function.
    supported_by:
    - reference_id: Reactome:R-HSA-1678742
      supporting_text: >-
        Alpha-N-acetylglucosaminidase (NAGLU) hydrolyses the non-reducing, terminal
        N-acetyl-D-glucosamine residue from heparan sulfate.
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2090038
  qualifier: enables
  review:
    summary: >-
      Reactome (TAS) annotation of the core catalytic activity in a second heparan chain
      hydrolysis reaction.
    action: ACCEPT
    reason: >-
      Same well-supported core molecular function as the other alpha-N-acetylglucosaminidase
      activity annotations, from a distinct Reactome reaction. Redundant but valid.
    supported_by:
    - reference_id: Reactome:R-HSA-1678742
      supporting_text: >-
        Alpha-N-acetylglucosaminidase (NAGLU) hydrolyses the non-reducing, terminal
        N-acetyl-D-glucosamine residue from heparan sulfate.
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2263496
  qualifier: enables
  review:
    summary: >-
      Reactome (TAS) annotation of the core catalytic activity, from a reaction contrasting
      wild-type with defective NAGLU.
    action: ACCEPT
    reason: >-
      Restates the core alpha-N-acetylglucosaminidase activity of NAGLU. Redundant with the
      other MF annotations but valid and correctly attributed.
    supported_by:
    - reference_id: Reactome:R-HSA-1678742
      supporting_text: >-
        Alpha-N-acetylglucosaminidase (NAGLU) hydrolyses the non-reducing, terminal
        N-acetyl-D-glucosamine residue from heparan sulfate.
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9036052
  qualifier: enables
  review:
    summary: >-
      Reactome (TAS) annotation of the core catalytic activity, from a further heparan chain
      hydrolysis reaction.
    action: ACCEPT
    reason: >-
      Restates the core alpha-N-acetylglucosaminidase activity. Redundant with the other MF
      annotations but valid.
    supported_by:
    - reference_id: Reactome:R-HSA-1678742
      supporting_text: >-
        Alpha-N-acetylglucosaminidase (NAGLU) hydrolyses the non-reducing, terminal
        N-acetyl-D-glucosamine residue from heparan sulfate.
- term:
    id: GO:0043202
    label: lysosomal lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2263496
  qualifier: located_in
  review:
    summary: >-
      Reactome (TAS) location annotation placing NAGLU in the lysosomal lumen, where it acts on
      soluble heparan sulfate fragments.
    action: ACCEPT
    reason: >-
      NAGLU is a soluble lysosomal hydrolase acting in the lysosomal lumen; this is the precise
      compartment for its activity and is core. Consistent with the lysosome annotations.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome.'
- term:
    id: GO:0043202
    label: lysosomal lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9036052
  qualifier: located_in
  review:
    summary: >-
      Reactome (TAS) location annotation to lysosomal lumen, from a second reaction.
    action: ACCEPT
    reason: >-
      Same well-supported core lysosomal-lumen location as the other lysosomal lumen
      annotation. Redundant but valid.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-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 mass-spectrometry (HDA) detection of NAGLU in exosomes isolated from
      expressed prostatic secretions in urine.
    action: KEEP_AS_NON_CORE
    reason: >-
      NAGLU was identified in a bulk shotgun-proteomics survey of urinary/prostatic exosomes.
      Presence of lysosomal enzymes in secreted extracellular vesicles is a real but peripheral
      observation and does not reflect the core lysosomal catabolic function of the enzyme.
      Retained as a non-core localization.
    supported_by:
    - reference_id: PMID:23533145
      supporting_text: >-
        exosome preparations were characterized by a shotgun proteomics procedure. In pooled
        EPS-urine exosome samples, ~900 proteins were detected.
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: IDA
  original_reference_id: PMID:21082674
  qualifier: located_in
  review:
    summary: >-
      Proteomic (IDA) detection of NAGLU among low-abundance proteins in human urinary exosomes.
    action: KEEP_AS_NON_CORE
    reason: >-
      NAGLU was detected in a targeted low-abundance urinary-exosome proteome. As with the other
      exosome annotations, this is a peripheral localization observation, not the core lysosomal
      function; retained as non-core.
    supported_by:
    - reference_id: PMID:21082674
      supporting_text: >-
        After analysis by nanoHPLC-chip-MS/MS, 512 proteins were identified
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: HDA
  original_reference_id: PMID:19056867
  qualifier: located_in
  review:
    summary: >-
      Large-scale mass-spectrometry (HDA) detection of NAGLU in the human urinary exosome
      proteome.
    action: KEEP_AS_NON_CORE
    reason: >-
      NAGLU was among the ~1132 proteins profiled in urinary exosomes by LC-MS/MS. Consistent
      with the other exosome detections; a real but non-core localization for a lysosomal
      hydrolase.
    supported_by:
    - reference_id: PMID:19056867
      supporting_text: >-
        the analysis identified 1132 proteins unambiguously
- term:
    id: GO:0043202
    label: lysosomal lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-1678742
  qualifier: located_in
  review:
    summary: >-
      Reactome (TAS) location annotation to lysosomal lumen, from the primary NAGLU heparan
      sulfate hydrolysis reaction.
    action: ACCEPT
    reason: >-
      Correct core compartment for NAGLU's soluble hydrolase activity, tied directly to the
      reaction in which it degrades heparan sulfate. Consistent with other lysosomal
      annotations.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome.'
- term:
    id: GO:0043202
    label: lysosomal lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-2090038
  qualifier: located_in
  review:
    summary: >-
      Reactome (TAS) location annotation to lysosomal lumen, from a second heparan hydrolysis
      reaction.
    action: ACCEPT
    reason: >-
      Same well-supported core lysosomal-lumen location. Redundant but valid.
    supported_by:
    - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
      supporting_text: 'SUBCELLULAR LOCATION: Lysosome.'
- term:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  evidence_type: TAS
  original_reference_id: PMID:8650226
  qualifier: enables
  review:
    summary: >-
      Author-statement (TAS) annotation of alpha-N-acetylglucosaminidase activity from the
      foundational paper that cloned NAGLU and defined Sanfilippo B as its deficiency.
    action: ACCEPT
    reason: >-
      This is the primary literature establishing NAGLU as alpha-N-acetylglucosaminidase: the
      cDNA/gene was cloned starting from purified enzyme, and the disease is defined by
      deficiency of this activity. Core molecular function, strongly supported.
    supported_by:
    - reference_id: PMID:8650226
      supporting_text: >-
        The Sanfilippo syndrome type B is a lysosomal storage disorder caused by
        deficiency of alpha-N-acetylglucosaminidase
- term:
    id: GO:0005764
    label: lysosome
  evidence_type: TAS
  original_reference_id: PMID:8650226
  qualifier: located_in
  review:
    summary: >-
      Author-statement (TAS) annotation of lysosomal localization from the foundational NAGLU
      cloning paper.
    action: ACCEPT
    reason: >-
      NAGLU is characterized as a lysosomal enzyme whose deficiency causes a lysosomal storage
      disorder; the lysosome is its established site of action. Core location, experimentally
      grounded.
    supported_by:
    - reference_id: PMID:8650226
      supporting_text: >-
        The Sanfilippo syndrome type B is a lysosomal storage disorder caused by
        deficiency of alpha-N-acetylglucosaminidase
- term:
    id: GO:0007399
    label: nervous system development
  evidence_type: TAS
  original_reference_id: PMID:8650226
  qualifier: involved_in
  review:
    summary: >-
      Author-statement (TAS) annotation to nervous system development, reflecting the profound
      neurological phenotype of NAGLU deficiency (Sanfilippo B).
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The neurological phenotype of MPS IIIB (profound mental deterioration, CNS degeneration)
      is a downstream pathological consequence of failed lysosomal heparan sulfate catabolism
      and progressive storage, not a direct developmental function of the enzyme. NAGLU is a
      housekeeping lysosomal glycosidase; annotating it to nervous system development conflates
      disease phenotype with molecular role and over-annotates. The core biology is captured by
      the catabolic-process and lysosome annotations.
    supported_by:
    - reference_id: PMID:8650226
      supporting_text: >-
        it is characterized by profound mental deterioration in childhood and death in the
        second decade
core_functions:
- description: >-
    Lysosomal alpha-N-acetylglucosaminidase that hydrolyses terminal non-reducing
    alpha-N-acetyl-D-glucosamine residues in heparan sulfate, carrying out one exolytic step
    in the stepwise lysosomal catabolism of heparan sulfate glycosaminoglycan.
  molecular_function:
    id: GO:0004561
    label: alpha-N-acetylglucosaminidase activity
  directly_involved_in:
  - id: GO:0030200
    label: heparan sulfate proteoglycan catabolic process
  locations:
  - id: GO:0043202
    label: lysosomal lumen
  - id: GO:0005764
    label: lysosome
  supported_by:
  - reference_id: file:human/NAGLU/NAGLU-uniprot.txt
    supporting_text: >-
      Reaction=Hydrolysis of terminal non-reducing N-acetyl-D-glucosamine
      residues in N-acetyl-alpha-D-glucosaminides.; EC=3.2.1.50
  - reference_id: Reactome:R-HSA-1678742
    supporting_text: >-
      Alpha-N-acetylglucosaminidase (NAGLU) hydrolyses the non-reducing, terminal
      N-acetyl-D-glucosamine residue from heparan sulfate.
  - reference_id: PMID:8650226
    supporting_text: >-
      The Sanfilippo syndrome type B is a lysosomal storage disorder caused by
      deficiency of alpha-N-acetylglucosaminidase
references:
- id: GO_REF:0000003
  title: Gene Ontology annotation based on Enzyme Commission mapping
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
    vocabulary mapping, accompanied by conservative changes to GO terms applied by
    UniProt
  findings: []
- id: GO_REF:0000117
  title: Electronic Gene Ontology annotations created by ARBA machine learning models
  findings: []
- id: PMID:19056867
  title: Large-scale proteomics and phosphoproteomics of urinary exosomes.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Bulk urinary-exosome proteomics; supports only the non-core extracellular exosome
      localization of NAGLU, not its lysosomal function.
- id: PMID:21082674
  title: Comprehensive analysis of low-abundance proteins in human urinary exosomes
    using peptide ligand library technology, peptide OFFGEL fractionation and nanoHPLC-chip-MS/MS.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Low-abundance urinary-exosome proteome; supports only non-core extracellular exosome
      detection of NAGLU.
- id: PMID:23533145
  title: In-depth proteomic analyses of exosomes isolated from expressed prostatic
    secretions in urine.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Prostatic-secretion exosome proteomics; supports only non-core extracellular exosome
      detection of NAGLU.
- id: PMID:8650226
  title: The molecular basis of Sanfilippo syndrome type B.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Foundational paper that cloned the NAGLU cDNA/gene and established that Sanfilippo
      syndrome type B is caused by deficiency of alpha-N-acetylglucosaminidase; supports the
      core molecular function and lysosomal localization.
- id: Reactome:R-HSA-1678742
  title: NAGLU hydrolyses Heparan sulfate chain(4)
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Directly describes NAGLU hydrolysing the terminal non-reducing N-acetyl-D-glucosamine
      of heparan sulfate; supports the core catalytic activity and heparan sulfate catabolism.
- id: Reactome:R-HSA-2024096
  title: HS-GAG degradation
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Pathway describing lysosomal degradation of heparan sulfate glycosaminoglycan; supports
      the core biological process annotation for NAGLU.
- id: Reactome:R-HSA-2090038
  title: NAGLU hydrolyses heparan chain(2)
  findings: []
- id: Reactome:R-HSA-2263496
  title: Defective NAGLU does not hydrolyse Heparan sulfate chain(4)
  findings: []
- id: Reactome:R-HSA-9036052
  title: Defective NAGLU does not hydrolyse heparan chain(2)
  findings: []
- id: file:human/NAGLU/NAGLU-uniprot.txt
  title: UniProtKB entry P54802 (ANAG_HUMAN), Alpha-N-acetylglucosaminidase
  findings: []