id: Q8N142
gene_symbol: ADSS1
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: Muscle (basic/M-type) isozyme of adenylosuccinate synthetase (AMPSase 1;
  synonym ADSSL1; EC 6.3.4.4), a cytosolic homodimeric enzyme predominantly expressed
  in skeletal muscle and heart. It catalyzes the first, committed step of the IMP-to-AMP
  branch of purine metabolism, the Mg2+-dependent, GTP-driven condensation of IMP with
  L-aspartate to form N6-(1,2-dicarboxyethyl)-AMP (adenylosuccinate/S-AMP), GDP and phosphate;
  adenylosuccinate lyase (ADSL) then cleaves S-AMP to AMP and fumarate. Together with ADSL,
  ADSS1 also runs the AMP-regenerating limb of the muscle purine nucleotide cycle, which
  interconverts IMP and AMP and contributes to muscle energetics (glycolysis) and
  ammoniagenesis. The paralog ADSS2 is the liver/ubiquitous (acidic) isozyme. Biallelic
  loss-of-function variants in ADSS1 cause adenylosuccinate synthetase 1 (ADSSL1)-related
  distal myopathy (MPD5), an autosomal recessive adolescent/adult-onset distal myopathy.
alternative_products:
- name: '1'
  id: Q8N142-1
- name: '2'
  id: Q8N142-2
  sequence_note: VSP_008421
existing_annotations:
- term:
    id: GO:0004019
    label: adenylosuccinate synthase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: Phylogenetically inferred adenylosuccinate synthase activity, the defining
      molecular function of ADSS1 and the entire adenylosuccinate synthetase family.
      This is directly confirmed experimentally for the human protein.
    action: ACCEPT
    reason: This is the core, well-supported molecular function. The IBA is grounded in a
      broad set of orthologs (E. coli purA, yeast, mouse muscle/non-muscle isozymes) and is
      confirmed for the human enzyme by direct assay (PMID:15786719) and by a mutation study
      (PMID:26506222).
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: Recombinant AdSSL1 protein possesses typical enzymatic activity to
        catalyze adenylosuccinate formation.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: Phylogenetically inferred cytoplasmic localization, consistent with the
      experimentally observed cytoplasmic localization of the human protein.
    action: ACCEPT
    reason: Adenylosuccinate synthetase is a soluble cytosolic enzyme across the family;
      the human protein was directly observed in the cytoplasm when overexpressed
      (PMID:15786719). Cytosol (GO:0005829) is the more precise term captured elsewhere.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: Overexpressed AdSSL1 protein in COS-7 cells locates in cytoplasm.
- term:
    id: GO:0044208
    label: "'de novo' AMP biosynthetic process"
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: Phylogenetically inferred role in de novo AMP biosynthesis. ADSS1 catalyzes
      step 1 of 2 of the conversion of IMP to AMP, the first committed step of the de novo
      AMP branch of purine metabolism.
    action: ACCEPT
    reason: This is a core biological process for the gene, matching the UniProt-annotated
      pathway (AMP biosynthesis via the de novo pathway, AMP from IMP, step 1 of 2). Well
      supported by orthology and by the enzyme's characterized reaction.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: Purine metabolism; AMP biosynthesis via de novo pathway; AMP
        from IMP
- term:
    id: GO:0046040
    label: IMP metabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: Phylogenetically inferred involvement in IMP metabolism. IMP is the direct
      substrate of adenylosuccinate synthase, consumed in the first committed step of
      AMP synthesis.
    action: ACCEPT
    reason: Accurate; ADSS1 consumes IMP (with GTP and aspartate) and, as part of the
      purine nucleotide cycle, contributes to IMP/AMP interconversion. Broader than the
      specific catalytic function but a correct process annotation.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: which catalyzes the first committed step in AMP synthesis
- term:
    id: GO:0000166
    label: nucleotide binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: InterPro-based inference of nucleotide binding. ADSS1 binds GTP (and its
      product GDP) and IMP as substrates; nucleotide binding is a general parent of these
      specific activities.
    action: ACCEPT
    reason: Correct but general. The enzyme has a P-loop NTPase fold and documented GTP/IMP
      binding sites (UniProt BINDING features). More specific GTP binding (GO:0005525) is
      also annotated. Retained as an accurate, if broad, molecular-function annotation.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: Nucleotide-binding
- term:
    id: GO:0000287
    label: magnesium ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000104
  qualifier: enables
  review:
    summary: Rule-based inference of magnesium ion binding. Adenylosuccinate synthase is
      a Mg2+-dependent enzyme that binds one Mg2+ ion per subunit, coordinating the
      GTP/phosphoryl-transfer chemistry.
    action: ACCEPT
    reason: Supported by UniProt cofactor and binding-site annotations (Mg2+ bound at
      residues 43 and 70), consistent with the conserved catalytic mechanism of the family.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: Binds 1 Mg(2+) ion per subunit.
- term:
    id: GO:0004019
    label: adenylosuccinate synthase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Automated (ARBA/UniRule/InterPro/RHEA/EC) inference of the core adenylosuccinate
      synthase activity, duplicating the experimentally and phylogenetically supported
      molecular function.
    action: ACCEPT
    reason: Correct core molecular function (EC 6.3.4.4; RHEA 15753), consistent with the
      IDA, IMP, and IBA annotations for the same term.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: Recombinant AdSSL1 protein possesses typical enzymatic activity to
        catalyze adenylosuccinate formation.
- term:
    id: GO:0005525
    label: GTP binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Automated inference of GTP binding. GTP is a required co-substrate of the
      adenylosuccinate synthase reaction, providing the energy for the ligation and being
      converted to GDP + phosphate.
    action: ACCEPT
    reason: Well supported; UniProt documents multiple GTP-binding regions (residues 42-48,
      70-72, 337, 363-365, 445-448) and the reaction consumes GTP. Also independently
      annotated NAS from PMID:15786719.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: N(6)-(1,2-dicarboxyethyl)-AMP + GDP
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: located_in
  review:
    summary: Automated inference of cytoplasmic localization, matching the experimental
      cytoplasmic localization and the cytosol annotation.
    action: ACCEPT
    reason: Consistent with UniProt subcellular location (Cytoplasm) and the direct
      experimental observation in PMID:15786719.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: Overexpressed AdSSL1 protein in COS-7 cells locates in cytoplasm.
- term:
    id: GO:0006164
    label: purine nucleotide biosynthetic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: InterPro-based inference of involvement in purine nucleotide biosynthesis.
      ADSS1 acts in the IMP-to-AMP branch, producing the purine nucleotide AMP.
    action: ACCEPT
    reason: Correct but general parent of the more specific AMP biosynthesis terms; retained
      as an accurate process annotation.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: which catalyzes the first committed step in AMP synthesis
- term:
    id: GO:0006167
    label: AMP biosynthetic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: Automated inference of involvement in AMP biosynthesis, the direct downstream
      product process of the adenylosuccinate synthase reaction (via ADSL cleavage of S-AMP
      to AMP). Also independently supported by IDA (PMID:15786719).
    action: ACCEPT
    reason: Core biological process; the enzyme catalyzes the committed step producing the
      AMP precursor adenylosuccinate.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: which catalyzes the first committed step in AMP synthesis
- term:
    id: GO:0044208
    label: "'de novo' AMP biosynthetic process"
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: Automated (UniRule/UniPathway) inference of the de novo AMP biosynthetic
      process, matching the IBA annotation and the UniProt pathway assignment.
    action: ACCEPT
    reason: Correct and specific core process (de novo AMP-from-IMP pathway, step 1 of 2).
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: AMP biosynthesis via de novo pathway
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:28514442
  qualifier: enables
  review:
    summary: IntAct proteome-scale interaction annotation (WITH/FROM UniProtKB:P30520,
      the paralog ADSS2). "Protein binding" is uninformative as a molecular function.
    action: MARK_AS_OVER_ANNOTATED
    reason: The bare GO:0005515 term conveys no specific function. The recorded partner is
      the paralog ADSS2, consistent with the UniProt-documented ADSS1-ADSS2 interaction, but
      this is a large-scale interactome dataset that does not establish a discrete functional
      MF for ADSS1. Per curation policy, retained (not removed) but flagged as
      over-annotation; the informative function is captured by GO:0004019.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: "Q8N142; P30520: ADSS2; NbExp=4"
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:33961781
  qualifier: enables
  review:
    summary: IntAct proteome-scale interaction annotation (WITH/FROM UniProtKB:P30520,
      the paralog ADSS2). Uninformative bare protein-binding term.
    action: MARK_AS_OVER_ANNOTATED
    reason: As above, a high-throughput interactome mapping to the paralog ADSS2. Retained
      per policy but flagged as over-annotation; adds no specific molecular function beyond
      the adenylosuccinate synthase activity.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: "Q8N142; P30520: ADSS2; NbExp=4"
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:40205054
  qualifier: enables
  review:
    summary: IntAct proteome-scale interaction annotation (WITH/FROM UniProtKB:P30520,
      the paralog ADSS2). Uninformative bare protein-binding term.
    action: MARK_AS_OVER_ANNOTATED
    reason: As above, a multimodal cell-map / interactome dataset mapping to ADSS2. Retained
      per policy but flagged as over-annotation.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: "Q8N142; P30520: ADSS2; NbExp=4"
- term:
    id: GO:0044209
    label: AMP salvage
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  qualifier: involved_in
  review:
    summary: Ensembl-orthology inference of involvement in AMP salvage. ADSS1 in muscle
      operates the AMP-regenerating limb of the purine nucleotide cycle (IMP to AMP), which
      recycles the purine nucleotide pool.
    action: MARK_AS_OVER_ANNOTATED
    reason: The primary and precise characterization of ADSS1 is de novo AMP biosynthesis
      (AMP from IMP, step 1 of 2). AMP salvage (reuse of preformed adenine/adenosine) is not
      the enzyme's committed-step chemistry; the overlap is via the purine nucleotide cycle
      that regenerates AMP from IMP. Kept as it is not strictly wrong, but flagged as a less
      precise, orthology-transferred process; GO:0044208 is the accurate term.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: which interconverts IMP and AMP to regulate the nucleotide levels
- term:
    id: GO:0004019
    label: adenylosuccinate synthase activity
  evidence_type: IMP
  original_reference_id: PMID:26506222
  qualifier: enables
  review:
    summary: Adenylosuccinate synthase activity inferred from mutant phenotype; disease
      variants in ADSSL1 reduce catalytic activity, confirming that the wild-type protein
      provides this function.
    action: ACCEPT
    reason: Direct genetic/functional evidence. Both MPD5 mutations (p.D304N and p.I350fs)
      decreased enzymatic activity, and the D261N variant characterized in UniProt shows
      decreased adenylosuccinate synthase activity, tying the human gene product's core
      catalytic function to disease.
    supported_by:
    - reference_id: PMID:26506222
      supporting_text: Both the D304N and I350fs mutations in ADSSL1 led to decreased
        enzymatic activity.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-111524
  qualifier: located_in
  review:
    summary: Cytosolic localization asserted by Reactome for the adenylosuccinate synthase
      reaction, consistent with the soluble cytosolic nature of the enzyme.
    action: ACCEPT
    reason: Cytosol is the precise cellular component for this soluble enzyme, agreeing with
      the experimental cytoplasm localization (PMID:15786719) and UniProt subcellular
      location. This is the preferred specific location term.
    supported_by:
    - reference_id: Reactome:R-HSA-111524
      supporting_text: Two isoforms of adenylosuccinate synthetase, ADSS and ADSSL1, catalyze
        the reaction of IMP, aspartate, and GTP to form adenylosuccinate, GDP, and
        orthophosphate
- term:
    id: GO:0002376
    label: immune system process
  evidence_type: NAS
  original_reference_id: PMID:15786719
  qualifier: involved_in
  review:
    summary: Non-traceable author statement based on the observation that AdSSL1 is
      expressed in hematopoietic/leukemia cell lines in a stimulation-dependent manner.
      This is an expression correlation, not an established immune function.
    action: KEEP_AS_NON_CORE
    reason: ADSS1 is fundamentally a purine-metabolism enzyme predominantly expressed in
      muscle; the immune-system link rests only on expression in leukemia cells after
      stimulation, with no demonstrated mechanistic immune role. Kept as a non-core,
      weakly-supported process rather than a core function.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: After stimulation, leukemia cells express AdSSL1 in a time-dependent
        manner
- term:
    id: GO:0004019
    label: adenylosuccinate synthase activity
  evidence_type: IDA
  original_reference_id: PMID:15786719
  qualifier: enables
  review:
    summary: Direct assay of recombinant human AdSSL1 demonstrating adenylosuccinate
      synthase activity (adenylosuccinate formation). This is the primary experimental
      evidence for the core molecular function.
    action: ACCEPT
    reason: Strong direct experimental support for the defining catalytic activity of the
      gene product.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: Recombinant AdSSL1 protein possesses typical enzymatic activity to
        catalyze adenylosuccinate formation.
- term:
    id: GO:0005525
    label: GTP binding
  evidence_type: NAS
  original_reference_id: PMID:15786719
  qualifier: enables
  review:
    summary: Author statement of GTP binding, reflecting the conserved GTP-dependent
      mechanism of adenylosuccinate synthetase; GTP is a co-substrate of the reaction.
    action: ACCEPT
    reason: Consistent with the well-characterized GTP-dependent catalytic mechanism and
      the multiple GTP-binding regions annotated in UniProt; also independently supported by
      IEA.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: N(6)-(1,2-dicarboxyethyl)-AMP + GDP
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:15786719
  qualifier: located_in
  review:
    summary: Direct experimental observation that overexpressed AdSSL1 localizes to the
      cytoplasm in COS-7 cells.
    action: ACCEPT
    reason: Direct localization evidence for the human protein; cytosol (GO:0005829) is the
      more granular equivalent captured from Reactome.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: Overexpressed AdSSL1 protein in COS-7 cells locates in cytoplasm.
- term:
    id: GO:0006167
    label: AMP biosynthetic process
  evidence_type: IDA
  original_reference_id: PMID:15786719
  qualifier: involved_in
  review:
    summary: Direct evidence linking ADSS1 to AMP biosynthesis via its characterized
      adenylosuccinate-forming activity, the committed step in AMP synthesis.
    action: ACCEPT
    reason: Core biological process, directly supported by the enzyme assay and the
      description of AdSSL1 as catalyzing the first committed step in AMP synthesis.
    supported_by:
    - reference_id: PMID:15786719
      supporting_text: which catalyzes the first committed step in AMP synthesis
- term:
    id: GO:0042301
    label: phosphate ion binding
  evidence_type: NAS
  original_reference_id: PMID:15786719
  qualifier: enables
  review:
    summary: Author statement of phosphate ion binding. Phosphate is a reaction product
      and the enzyme binds the phosphate groups of its GTP/GDP and IMP ligands, but a
      standalone phosphate-ion-binding molecular function is not informative for this
      enzyme.
    action: MARK_AS_OVER_ANNOTATED
    reason: The enzyme's phosphate handling is part of GTP binding and the ligase catalytic
      mechanism (phosphate is released as a product). A discrete phosphate-ion-binding MF
      annotation adds little and risks over-representing an incidental feature; the
      informative functions are GO:0004019 and GO:0005525. Kept (not wrong) but flagged.
    supported_by:
    - reference_id: file:human/ADSS1/ADSS1-uniprot.txt
      supporting_text: N(6)-(1,2-dicarboxyethyl)-AMP + GDP
        + phosphate
core_functions:
- description: Catalyzes the first committed step of AMP biosynthesis from IMP - the
    Mg2+-dependent, GTP-driven condensation of IMP with L-aspartate to yield
    adenylosuccinate (N6-(1,2-dicarboxyethyl)-AMP), GDP and phosphate (EC 6.3.4.4) - as the
    muscle isozyme of adenylosuccinate synthetase.
  molecular_function:
    id: GO:0004019
    label: adenylosuccinate synthase activity
  directly_involved_in:
  - id: GO:0044208
    label: "'de novo' AMP biosynthetic process"
  - id: GO:0006167
    label: AMP biosynthetic process
  supported_by:
  - reference_id: PMID:15786719
    supporting_text: Recombinant AdSSL1 protein possesses typical enzymatic activity to
      catalyze adenylosuccinate formation.
  - reference_id: PMID:26506222
    supporting_text: Both the D304N and I350fs mutations in ADSSL1 led to decreased
      enzymatic activity.
  locations:
  - id: GO:0005829
    label: cytosol
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO
    terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings: []
- id: GO_REF:0000104
  title: Electronic Gene Ontology annotations created by transferring manual GO annotations
    between related proteins based on shared sequence features
  findings: []
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to
    orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:15786719
  title: Molecular cloning and characterization of a novel muscle adenylosuccinate
    synthetase, AdSSL1, from human bone marrow stromal cells.
  findings:
  - statement: Human AdSSL1 is the muscle isozyme of adenylosuccinate synthetase that
      catalyzes the first committed step in AMP synthesis; recombinant protein has typical
      adenylosuccinate synthase activity and the protein localizes to the cytoplasm.
    supporting_text: Recombinant AdSSL1 protein possesses typical enzymatic activity to
      catalyze adenylosuccinate formation.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; primary characterization of human ADSS1/AdSSL1
      (activity, cytoplasmic localization, muscle-predominant expression). Abstract-only in
      cache but the abstract directly supports the enzymatic and localization annotations.
- id: PMID:26506222
  title: ADSSL1 mutation relevant to autosomal recessive adolescent onset distal myopathy.
  findings:
  - statement: Biallelic ADSSL1 mutations cause autosomal recessive adolescent-onset distal
      myopathy (MPD5); the mutations decrease adenylosuccinate synthase enzymatic activity.
    supporting_text: Both the D304N and I350fs mutations in ADSSL1 led to decreased
      enzymatic activity.
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-verified; establishes the disease link (MPD5) and provides
      mutant-phenotype (IMP) evidence for the catalytic function. Abstract-only in cache;
      the abstract supports the activity and disease claims.
- id: PMID:28514442
  title: Architecture of the human interactome defines protein communities and disease
    networks.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Proteome-scale interactome study; source of an IntAct IPI protein-binding
      annotation (partner ADSS2). Does not establish a specific molecular function for ADSS1.
- id: PMID:33961781
  title: Dual proteome-scale networks reveal cell-specific remodeling of the human
    interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Proteome-scale interactome study; source of an IntAct IPI protein-binding
      annotation (partner ADSS2). Uninformative bare protein-binding evidence for ADSS1.
- id: PMID:40205054
  title: Multimodal cell maps as a foundation for structural and functional genomics.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: Multimodal cell-map / interactome study; source of an IntAct IPI
      protein-binding annotation (partner ADSS2). Uninformative bare protein-binding evidence.
- id: Reactome:R-HSA-111524
  title: IMP + L-Aspartate + GTP => Adenylosuccinate + GDP + Pi [ADSS]
  findings:
  - statement: Adenylosuccinate synthetase isoforms (including ADSSL1) catalyze the reaction
      of IMP, aspartate, and GTP to form adenylosuccinate, GDP and orthophosphate in the
      cytosol.
    supporting_text: Two isoforms of adenylosuccinate synthetase, ADSS and ADSSL1, catalyze
      the reaction of IMP, aspartate, and GTP to form adenylosuccinate, GDP, and
      orthophosphate
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Reactome reaction for the adenylosuccinate synthase step; source of the
      cytosol (TAS) localization. Title left exactly as fetched.
- id: file:human/ADSS1/ADSS1-uniprot.txt
  title: UniProt entry Q8N142 (PURA1_HUMAN, ADSS1) - adenylosuccinate synthetase isozyme 1
  findings:
  - statement: ADSS1 catalyzes the Mg2+-dependent, GTP-dependent reaction of IMP with
      L-aspartate to form adenylosuccinate, GDP and phosphate, the first committed step
      (step 1 of 2) of the de novo AMP-from-IMP pathway; it is a cytoplasmic homodimer that
      interacts with the paralog ADSS2.
    supporting_text: N(6)-(1,2-dicarboxyethyl)-AMP + GDP
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Curated UniProt record; primary source for reaction, cofactor, pathway,
      subcellular location, and the ADSS1-ADSS2 interaction used in this review.
suggested_questions:
- question: Does ADSS1 have non-catalytic or muscle-specific regulatory roles beyond the
    purine nucleotide cycle that explain the tissue-restricted, distal-predominant myopathy
    phenotype, given the ubiquitously expressed paralog ADSS2?
- question: Is the observed expression of AdSSL1 in stimulated leukemia/hematopoietic cells
    associated with any genuine immune function, or purely a metabolic response?
suggested_experiments:
- description: Steady-state kinetic characterization of purified recombinant human ADSS1
    (Km for IMP, L-aspartate, GTP; Mg2+ dependence) compared with ADSS2, to quantify the
    muscle isozyme's catalytic properties.
  hypothesis: The muscle isozyme ADSS1 has kinetic properties distinct from ADSS2 that suit
    the high purine-nucleotide-cycle flux of skeletal muscle.
- description: Muscle-specific Adss1 knockout or knock-in of the MPD5 D304N variant in mouse
    to test whether purine nucleotide cycle disruption drives the distal myopathy phenotype.
  hypothesis: Loss of ADSS1 catalytic activity impairs the muscle purine nucleotide cycle,
    causing the distal myopathy seen in MPD5 patients.