id: Q88C48
gene_symbol: purK
product_type: PROTEIN
status: DRAFT
taxon:
  id: NCBITaxon:160488
  label: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB 11950 / KT2440)
description: PurK is the ATP-dependent N5-CAIR synthetase that carboxylates AIR to N5-CAIR. PurE then
  rearranges N5-CAIR to CAIR, so the bacterial AIR-carboxylation stage is divided between two enzymes.
existing_annotations:
- term:
    id: GO:0000166
    label: nucleotide binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000104
  qualifier: enables
  review:
    summary: Valid substrate binding, but not the core function of PurK.
    action: KEEP_AS_NON_CORE
    reason: Nucleotide binding supports catalysis, while the enzyme-specific activity captures the core function.
- term:
    id: GO:0004638
    label: phosphoribosylaminoimidazole carboxylase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: The pathway position is correct, but the term describes direct AIR carboxylation.
    action: MODIFY
    reason: Replace the direct carboxylase activity with the specific PurK N5-CAIR synthetase activity.
    proposed_replacement_terms:
    - id: GO:0034028
      label: 5-(carboxyamino)imidazole ribonucleotide synthase activity
- term:
    id: GO:0005524
    label: ATP binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Valid substrate binding, but not the core function of PurK.
    action: KEEP_AS_NON_CORE
    reason: ATP is consumed by the synthetase reaction, while the enzyme-specific activity captures the core function.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IEA
  original_reference_id: GO_REF:0000118
  qualifier: located_in
  review:
    summary: Correct specific location for a soluble bacterial enzyme.
    action: ACCEPT
    reason: The enzyme acts on soluble intermediates of de novo purine synthesis.
- term:
    id: GO:0006189
    label: '''de novo'' IMP biosynthetic process'
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: involved_in
  review:
    summary: Correct pathway assignment.
    action: ACCEPT
    reason: This enzyme catalyzes a required reaction between PRPP and IMP.
- term:
    id: GO:0034028
    label: 5-(carboxyamino)imidazole ribonucleotide synthase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: Correct enzyme-specific molecular function.
    action: ACCEPT
    reason: The exact N5-carboxyaminoimidazole ribonucleotide synthase product assignment supports this
      activity.
- term:
    id: GO:0046872
    label: metal ion binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: Valid cofactor binding, but not the core function of PurK.
    action: KEEP_AS_NON_CORE
    reason: Metal binding supports catalysis, while the enzyme-specific activity captures the core function.
references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  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:0000118
  title: TreeGrafter-generated GO annotations
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:10574791
  title: Crystal structure of Escherichia coli PurE, an unusual mutase in the purine biosynthetic
    pathway.
  full_text_unavailable: true
  findings:
  - statement: The bacterial AIR-carboxylation route requires PurK and PurE, with PurK supplying
      the N5-CAIR intermediate.
    supporting_text: >-
      Conversion of 5-aminoimidazole ribonucleotide (AIR) to
      4-carboxyaminoimidazole ribonucleotide (CAIR) in Escherichia coli
      requires two proteins - PurK and PurE.
    reference_section_type: RESULTS
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: PubMed-cached abstract-only primary research; supports the two-enzyme route
      architecture but is not direct characterization of the P. putida protein.
- id: file:PSEPK/purK/purK-uniprot.txt
  title: UniProtKB entry Q88C48 for Pseudomonas putida KT2440 purK
  findings:
  - statement: UniProt identifies Q88C48 as N5-carboxyaminoimidazole ribonucleotide synthase.
    supporting_text: 'RecName: Full=N5-carboxyaminoimidazole ribonucleotide synthase'
    reference_section_type: RESULTS
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: Exact target accession and product line in the fetched UniProt record.
core_functions:
- description: Forms N5-CAIR in the first half of the bacterial AIR-carboxylation stage.
  molecular_function:
    id: GO:0034028
    label: 5-(carboxyamino)imidazole ribonucleotide synthase activity
  directly_involved_in:
  - id: GO:0006189
    label: '''de novo'' IMP biosynthetic process'
  supported_by:
  - reference_id: file:PSEPK/purK/purK-uniprot.txt
    supporting_text: 'RecName: Full=N5-carboxyaminoimidazole ribonucleotide synthase'
  - reference_id: PMID:10574791
    supporting_text: >-
      Conversion of 5-aminoimidazole ribonucleotide (AIR) to
      4-carboxyaminoimidazole ribonucleotide (CAIR) in Escherichia coli
      requires two proteins - PurK and PurE.
  locations:
  - id: GO:0005829
    label: cytosol
suggested_experiments:
- description: Test a clean purK deletion for purine auxotrophy and rescue by the appropriate downstream
    purine intermediate or by gene complementation.