id: P00491
gene_symbol: PNP
product_type: PROTEIN
status: INITIALIZED
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >-
  Purine nucleoside phosphorylase (PNP; EC 2.4.2.1) is a cytosolic homotrimeric
  enzyme of purine catabolism and salvage. It catalyzes the reversible
  phosphorolysis of the N-glycosidic bond of 6-oxopurine (deoxy)ribonucleosides,
  converting inosine, guanosine and their 2'-deoxy forms (plus phosphate) to the
  corresponding free purine base (hypoxanthine or guanine) and
  (2'-deoxy)-alpha-D-ribose-1-phosphate. The liberated bases are either recycled
  by salvage (e.g. by HPRT1) or channeled into oxidative catabolism (hypoxanthine
  to xanthine to urate by xanthine oxidoreductase). PNP is highly specific for
  6-oxopurine nucleosides and essentially inactive on adenine (6-amino) nucleosides.
  It also phosphorolyses the pyridine nucleoside nicotinamide riboside, contributing
  to a kinase-independent NAD+ salvage route. In humans, loss-of-function of PNP
  causes purine nucleoside phosphorylase deficiency, an autosomal recessive disorder
  in which accumulating (deoxy)guanosine and dGTP are toxic to T lymphocytes,
  producing a severe T-cell immunodeficiency (a cause of severe combined
  immunodeficiency) frequently accompanied by neurological impairment.
existing_annotations:
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: enables
  review:
    summary: >-
      Core molecular function of PNP: phosphorolytic cleavage of purine
      (deoxy)ribonucleosides. Phylogenetic (IBA) annotation consistent with
      abundant human experimental evidence.
    action: ACCEPT
    reason: >-
      This is the well-established core catalytic activity of PNP (EC 2.4.2.1),
      directly demonstrated for the human enzyme by multiple experimental studies.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
    - reference_id: PMID:23438750
      supporting_text: "catalyzes the reversible phosphorolysis of purine (deoxy)-ribonucleosides to the corresponding purine base"
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: is_active_in
  review:
    summary: >-
      PNP is a soluble cytosolic enzyme; phylogenetic assignment of cytosolic
      localization is correct and matches direct evidence in human cells.
    action: ACCEPT
    reason: >-
      UniProt records the subcellular location as Cytoplasm, cytosol, and human
      immunofluorescence (HPA) and direct assays place PNP in the cytosol; this is
      the site of its catalytic function.
- term:
    id: GO:0006148
    label: inosine catabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses inosine to hypoxanthine, a committed step of inosine
      catabolism/salvage. Core biological process.
    action: ACCEPT
    reason: >-
      Directly demonstrated: purified human PNP catalyzes phosphorolysis of inosine,
      supporting its role in inosine catabolism.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0006149
    label: deoxyinosine catabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses 2'-deoxyinosine to hypoxanthine; part of its core
      (deoxy)nucleoside catabolic activity.
    action: ACCEPT
    reason: >-
      Purified human PNP catalyzes deoxyinosine phosphorolysis, and the enzyme acts
      equally on ribo- and deoxyribonucleosides of 6-oxopurines.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0006161
    label: deoxyguanosine catabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses 2'-deoxyguanosine to guanine; a core catabolic step and
      the one most relevant to PNP-deficiency pathology (dGTP accumulation).
    action: ACCEPT
    reason: >-
      Purified human PNP catalyzes deoxyguanosine phosphorolysis; failure of this
      step underlies the T-cell-toxic (deoxy)guanosine/dGTP buildup in PNP deficiency.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0034355
    label: NAD+ biosynthetic process via the salvage pathway
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses nicotinamide riboside (NR) to nicotinamide, providing a
      kinase-independent entry into NAD+ salvage. Real but not the core catabolic
      function of PNP.
    action: KEEP_AS_NON_CORE
    reason: >-
      Mammalian PNP is the enzyme responsible for Nrk1-independent NR utilization,
      cleaving NR (and nicotinic acid riboside) to feed NAD+ salvage; this is a
      secondary/alternative-substrate role downstream of nucleoside phosphorolysis
      rather than PNP's principal purine-catabolic function.
    supported_by:
    - reference_id: PMID:19001417
      supporting_text: "that mammalian purine nucleoside phosphorylase but not methylthioadenosine"
- term:
    id: GO:0046115
    label: guanosine catabolic process
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses guanosine to guanine; a core catabolic/salvage step.
    action: ACCEPT
    reason: >-
      Purified human PNP catalyzes guanosine phosphorolysis with high affinity
      (KM ~6 uM), a core substrate of the enzyme.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0003824
    label: catalytic activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      Root-level catalytic activity term from InterPro mapping; uninformative given
      the specific EC 2.4.2.1 activity is annotated.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      GO:0003824 is the most general molecular-function term and conveys nothing
      beyond the specific purine-nucleoside phosphorylase activity already annotated.
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  qualifier: enables
  review:
    summary: >-
      Same core molecular function via automated EC/RHEA/ARBA mapping; correct.
    action: ACCEPT
    reason: >-
      Automated mapping (EC 2.4.2.1 / RHEA:27646) to purine-nucleoside phosphorylase
      activity is accurate and matches experimental evidence.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  qualifier: located_in
  review:
    summary: >-
      Cytosol from UniProt subcellular-location keyword mapping; correct.
    action: ACCEPT
    reason: >-
      Consistent with the curated Cytoplasm/cytosol location and direct human
      evidence.
- term:
    id: GO:0009116
    label: nucleoside metabolic process
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: involved_in
  review:
    summary: >-
      Broad but correct parent process (nucleoside metabolism) from InterPro mapping.
    action: KEEP_AS_NON_CORE
    reason: >-
      Accurate as a general process term but less informative than the specific
      purine (deoxy)nucleoside catabolic/salvage terms already present.
- term:
    id: GO:0016763
    label: pentosyltransferase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  qualifier: enables
  review:
    summary: >-
      Correct parent MF (PNP is a glycosyltransferase/pentosyltransferase, EC 2.4.2)
      but broader than the specific activity.
    action: KEEP_AS_NON_CORE
    reason: >-
      GO:0016763 is the accurate broad classification of the reaction chemistry;
      retained as a non-core parent of purine-nucleoside phosphorylase activity.
- term:
    id: GO:0047975
    label: guanosine phosphorylase activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000116
  qualifier: enables
  review:
    summary: >-
      Substrate-specific child activity (guanosine + phosphate = guanine +
      ribose-1-phosphate); correct via RHEA mapping.
    action: ACCEPT
    reason: >-
      PNP has robust guanosine phosphorylase activity (KM ~6 uM), a specific facet of
      its EC 2.4.2.1 activity; automated RHEA:13233 mapping is correct.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32814053
  qualifier: enables
  review:
    summary: >-
      Uninformative "protein binding" from a large-scale neurodegenerative-disease
      Y2H interactome screen; multiple heterogeneous partners with no defined
      functional consequence for PNP.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      This and the other GO:0005515 IPI lines derive from high-throughput binary
      interactome mapping (yeast two-hybrid); the term is non-specific and does not
      inform PNP's molecular function. Retained (not removed) per curation policy on
      experimental IPI, but flagged as over-annotation.
    supported_by:
    - reference_id: PMID:32814053
      supporting_text: "generated by systematic yeast two-hybrid"
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:20212140
  qualifier: enables
  review:
    summary: >-
      Self-association reflecting PNP's obligate homotrimeric quaternary structure;
      biologically meaningful.
    action: ACCEPT
    reason: >-
      Human PNP is a homotrimer with catalytic sites at subunit interfaces, so
      identical-protein (self) binding is a genuine structural property of the enzyme.
    supported_by:
    - reference_id: PMID:20212140
      supporting_text: "Four generations of transition-state analogues for human purine nucleoside"
    additional_reference_ids:
    - PMID:23438750
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:25502805
  qualifier: enables
  review:
    summary: >-
      Self-association consistent with the homotrimeric architecture of PNP.
    action: ACCEPT
    reason: >-
      Homotrimer formation is a well-established structural feature; identical
      protein binding is appropriate.
    supported_by:
    - reference_id: PMID:23438750
      supporting_text: "Human PNP is a homotrimer"
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:31515488
  qualifier: enables
  review:
    summary: >-
      Self-association consistent with the homotrimeric architecture of PNP.
    action: ACCEPT
    reason: >-
      Homotrimer formation is a well-established structural feature; identical
      protein binding is appropriate.
    supported_by:
    - reference_id: PMID:23438750
      supporting_text: "Human PNP is a homotrimer"
- term:
    id: GO:0042802
    label: identical protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  qualifier: enables
  review:
    summary: >-
      Self-association consistent with the homotrimeric architecture of PNP.
    action: ACCEPT
    reason: >-
      Homotrimer formation is a well-established structural feature; identical
      protein binding is appropriate.
    supported_by:
    - reference_id: PMID:23438750
      supporting_text: "Human PNP is a homotrimer"
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: GO_REF:0000052
  qualifier: located_in
  review:
    summary: >-
      Direct immunofluorescence (HPA) localization to cytosol; correct core location.
    action: ACCEPT
    reason: >-
      Direct human-cell evidence for cytosolic localization, the functional site of
      the enzyme.
- term:
    id: GO:0047975
    label: guanosine phosphorylase activity
  evidence_type: EXP
  original_reference_id: PMID:9305964
  qualifier: enables
  review:
    summary: >-
      Experimentally measured guanosine phosphorylase activity (a specific facet of
      EC 2.4.2.1) for human PNP.
    action: ACCEPT
    reason: >-
      Kinetic characterization of human PNP includes guanosine as a high-affinity
      substrate, supporting guanosine phosphorylase activity.
    supported_by:
    - reference_id: PMID:9305964
      supporting_text: "highly specific for 6-oxopurine"
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: enables
  review:
    summary: >-
      Direct assay of purified human (granulocyte) PNP demonstrating phosphorolysis
      of 6-oxopurine (deoxy)nucleosides. Core function.
    action: ACCEPT
    reason: >-
      Purified human enzyme catalyzes phosphorolysis of inosine, deoxyinosine,
      guanosine and deoxyguanosine, directly establishing the activity.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0006149
    label: deoxyinosine catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      PNP phosphorolyses 2'-deoxyinosine (to hypoxanthine); part of deoxyinosine
      catabolism.
    action: ACCEPT
    reason: >-
      Directly demonstrated deoxyinosine phosphorolysis by the purified human enzyme.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0006157
    label: deoxyadenosine catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      Pathway-level (acts_upstream_of_or_within) annotation for deoxyadenosine
      catabolism. PNP does not act directly on deoxyadenosine (an adenine
      nucleoside), but participates downstream in the pathway after deamination.
    action: KEEP_AS_NON_CORE
    reason: >-
      The cited paper explicitly states that adenine (deoxy)ribonucleosides are NOT
      substrates of PNP, so this is not a direct enzymatic activity; however the
      curator's acts_upstream_of_or_within annotation reflects PNP's downstream role
      in the broader deoxyadenosine catabolic pathway (relevant to the dATP/dGTP
      accumulation of PNP deficiency). Retained as non-core rather than removed.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "ribonucleosides and deoxyribonucleosides of adenine and the pyrimidines are not"
- term:
    id: GO:0006204
    label: IMP catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      Pathway-level annotation for IMP catabolism. PNP acts on inosine (the
      dephosphorylated nucleoside), not on IMP directly, but functions downstream in
      the IMP-degradation pathway.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP's substrate is inosine (from IMP after 5'-nucleotidase), not IMP itself;
      the acts_upstream_of_or_within qualifier captures its downstream role in the
      IMP catabolic pathway. Retained as non-core.
- term:
    id: GO:0046059
    label: dAMP catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      Pathway-level annotation for dAMP catabolism. PNP does not act on dAMP or on
      adenine deoxynucleosides directly; downstream/pathway-context annotation.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP does not phosphorolyse adenine nucleosides (the paper states adenine
      deoxyribonucleosides are not substrates) and acts on nucleosides not
      nucleotides; the annotation reflects downstream pathway participation.
      Retained as non-core rather than removed for an experimental IDA.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "ribonucleosides and deoxyribonucleosides of adenine and the pyrimidines are not"
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9735775
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (defective-PNP inosine reaction); correct
      core location.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9735789
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (defective-PNP guanosine reaction); correct.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0006149
    label: deoxyinosine catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: involved_in
  review:
    summary: >-
      Duplicate (involved_in) annotation of deoxyinosine catabolism; directly
      supported.
    action: ACCEPT
    reason: >-
      Direct assay of deoxyinosine phosphorolysis by purified human PNP.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
- term:
    id: GO:0006157
    label: deoxyadenosine catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: involved_in
  review:
    summary: >-
      involved_in duplicate of the deoxyadenosine-catabolism pathway annotation.
      PNP does not act on deoxyadenosine directly.
    action: KEEP_AS_NON_CORE
    reason: >-
      As above: adenine deoxyribonucleosides are not PNP substrates, so this
      reflects a downstream/pathway role rather than a direct activity; retained as
      non-core.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "ribonucleosides and deoxyribonucleosides of adenine and the pyrimidines are not"
- term:
    id: GO:0006204
    label: IMP catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: involved_in
  review:
    summary: >-
      involved_in duplicate of the IMP-catabolism pathway annotation; PNP acts on
      inosine downstream of IMP.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP's direct substrate is inosine, not IMP; retained as a downstream
      pathway-level annotation.
- term:
    id: GO:0000255
    label: allantoin metabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: involved_in
  review:
    summary: >-
      Allantoin metabolism is several steps downstream of PNP (via urate) and does
      not occur in humans, who lack urate oxidase; this appears to be an
      over-propagated/incorrect pathway annotation for the human gene.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The cited human granulocyte study characterizes PNP nucleoside phosphorolysis
      and does not address allantoin; humans do not synthesize allantoin (uricase is
      a pseudogene), so an allantoin metabolic process annotation is not appropriate
      for human PNP. Flagged as over-annotation rather than removed, since it is an
      experimental IDA whose full text was not reviewed here.
- term:
    id: GO:0046059
    label: dAMP catabolic process
  evidence_type: IDA
  original_reference_id: PMID:6771276
  qualifier: involved_in
  review:
    summary: >-
      involved_in duplicate of the dAMP-catabolism pathway annotation; PNP acts on
      nucleosides, not dAMP, and not on adenine nucleosides.
    action: KEEP_AS_NON_CORE
    reason: >-
      Retained as a downstream pathway-level annotation; PNP does not directly act on
      dAMP or adenine (deoxy)nucleosides.
    supported_by:
    - reference_id: PMID:6771276
      supporting_text: "ribonucleosides and deoxyribonucleosides of adenine and the pyrimidines are not"
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:5056638
  qualifier: enables
  review:
    summary: >-
      PNP enzymatic activity measured in human erythrocytes; supports the core
      molecular function.
    action: ACCEPT
    reason: >-
      Human erythrocyte PNP activity assay supports the enzyme's phosphorylase
      activity (abstract-only cache; defer to the experimental curator).
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:23438750
  qualifier: enables
  review:
    summary: >-
      Kinetic/structural characterization of human PNP demonstrating phosphorolysis
      of purine (deoxy)ribonucleosides. Core function.
    action: ACCEPT
    reason: >-
      Directly establishes reversible phosphorolysis of purine (deoxy)ribonucleosides
      by the human enzyme, including steady-state kinetics for inosine.
    supported_by:
    - reference_id: PMID:23438750
      supporting_text: "catalyzes the reversible phosphorolysis of purine (deoxy)-ribonucleosides to the corresponding purine base"
- term:
    id: GO:0006148
    label: inosine catabolic process
  evidence_type: IDA
  original_reference_id: PMID:23438750
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses inosine (to hypoxanthine); core catabolic step, kinetically
      characterized.
    action: ACCEPT
    reason: >-
      Inosine phosphorolysis is directly characterized (steady-state kinetics) for
      the human enzyme.
    supported_by:
    - reference_id: PMID:23438750
      supporting_text: "catalyzes the reversible phosphorolysis of purine (deoxy)-ribonucleosides to the corresponding purine base"
- term:
    id: GO:0043101
    label: purine-containing compound salvage
  evidence_type: IDA
  original_reference_id: PMID:18938130
  qualifier: involved_in
  review:
    summary: >-
      PNP participates in purine salvage by generating free bases (hypoxanthine,
      guanine) for re-use; core biological role.
    action: ACCEPT
    reason: >-
      PNP's phosphorolysis of purine nucleosides yields free bases that are salvaged
      (e.g. by HPRT1); the reaction equilibrium in vivo also supports nucleoside
      (re)synthesis, consistent with a salvage role. UniProt assigns the pathway
      "purine nucleoside salvage".
- term:
    id: GO:0009165
    label: nucleotide biosynthetic process
  evidence_type: IGI
  original_reference_id: PMID:19001417
  qualifier: involved_in
  review:
    summary: >-
      Broad "nucleotide biosynthetic process" from a genetic-interaction study of NR
      salvage; PNP itself catabolizes nucleosides, so nucleotide biosynthesis is an
      over-broad downstream framing.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      PNP produces free bases/ribose-1-phosphate that can be recycled into
      nucleotides via salvage, but PNP is a phosphorylase (nucleoside catabolism),
      and GO:0009165 is a broad biosynthetic term better assigned to the downstream
      salvage kinases. The specific NR-catabolism and salvage terms already capture
      the relevant biology.
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6798748
  qualifier: located_in
  review:
    summary: >-
      Extracellular localization via Reactome neutrophil-degranulation
      (secretory-granule exocytosis) pathway; PNP is detected extracellularly but
      this is not its functional compartment.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP is a cytosolic enzyme released during neutrophil degranulation/secretion
      and detected in the extracellular space; not the site of its catalytic function.
- term:
    id: GO:0005576
    label: extracellular region
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6800434
  qualifier: located_in
  review:
    summary: >-
      Extracellular localization via Reactome ficolin-rich-granule exocytosis;
      detected extracellularly, non-functional compartment.
    action: KEEP_AS_NON_CORE
    reason: >-
      Same as the secretory-granule route: released cytosolic protein, not the
      functional location.
- term:
    id: GO:0034774
    label: secretory granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6798748
  qualifier: located_in
  review:
    summary: >-
      Secretory-granule-lumen localization from neutrophil-degranulation Reactome
      pathway; reflects presence in granules, not functional site.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP is packaged in neutrophil granules and released on degranulation; a
      non-core localization for a cytosolic enzyme.
- term:
    id: GO:1904813
    label: ficolin-1-rich granule lumen
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-6800434
  qualifier: located_in
  review:
    summary: >-
      Ficolin-1-rich granule lumen from neutrophil-degranulation Reactome; non-core
      localization.
    action: KEEP_AS_NON_CORE
    reason: >-
      Reflects granule content in neutrophils, not the cytosolic functional site.
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: HDA
  original_reference_id: PMID:23533145
  qualifier: located_in
  review:
    summary: >-
      Detected in extracellular exosomes by high-throughput proteomics; PNP is an
      abundant cytosolic protein commonly captured in exosome preparations.
    action: KEEP_AS_NON_CORE
    reason: >-
      Exosome proteomics frequently recovers abundant cytosolic enzymes; this does
      not indicate a functional exosomal role for PNP.
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: HDA
  original_reference_id: PMID:19056867
  qualifier: located_in
  review:
    summary: >-
      Detected in urinary exosomes by proteomics; non-functional localization.
    action: KEEP_AS_NON_CORE
    reason: >-
      High-throughput exosome/proteomics detection of an abundant cytosolic enzyme;
      not its functional compartment.
- term:
    id: GO:0070062
    label: extracellular exosome
  evidence_type: HDA
  original_reference_id: PMID:20458337
  qualifier: located_in
  review:
    summary: >-
      Detected in B-cell exosomes by proteomics; non-functional localization.
    action: KEEP_AS_NON_CORE
    reason: >-
      As above; proteomic detection in exosomes does not establish a functional role.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-112033
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (PNP inosine synthesis reaction); correct
      core location.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-112034
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (PNP guanosine synthesis reaction); correct.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74242
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (PNP inosine phosphorolysis); correct.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-74249
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (PNP guanosine phosphorolysis); correct.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9755044
  qualifier: located_in
  review:
    summary: >-
      Cytosol localization from Reactome (PNP-mediated ribavirin transformation);
      correct core location.
    action: ACCEPT
    reason: >-
      Consistent with the established cytosolic site of PNP function.
- term:
    id: GO:0032743
    label: positive regulation of interleukin-2 production
  evidence_type: IMP
  original_reference_id: PMID:16930574
  qualifier: involved_in
  review:
    summary: >-
      Restoring PNP in PNP-deficient T lymphocytes corrects IL-2 secretion; an
      indirect, downstream immunological consequence of the metabolic enzyme.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP does not directly regulate IL-2 transcription; loss of PNP causes
      dGTP-mediated T-cell dysfunction, and enzyme replacement rescues IL-2
      secretion. This is a physiological consequence, not a core molecular role.
    supported_by:
    - reference_id: PMID:16930574
      supporting_text: "functions of PNP-deficient T lymphocytes including their response to stimulation"
- term:
    id: GO:0001882
    label: nucleoside binding
  evidence_type: IDA
  original_reference_id: PMID:9305962
  qualifier: enables
  review:
    summary: >-
      PNP binds its purine-nucleoside substrate in the active site; supporting
      molecular function underlying catalysis.
    action: ACCEPT
    reason: >-
      Structure-function studies define the purine-binding/active site of human PNP
      that engages the nucleoside substrate.
    supported_by:
    - reference_id: PMID:9305962
      supporting_text: "Purine nucleoside phosphorylase. 1. Structure-function studies."
- term:
    id: GO:0002060
    label: purine nucleobase binding
  evidence_type: IDA
  original_reference_id: PMID:9305962
  qualifier: enables
  review:
    summary: >-
      PNP binds the purine base (product/substrate) in its active site; supporting
      MF consistent with structural studies.
    action: ACCEPT
    reason: >-
      The purine base binding site (Asn243/Glu201) is defined by structure-function
      mutagenesis; base binding is integral to the phosphorolysis reaction.
    supported_by:
    - reference_id: PMID:9305962
      supporting_text: "Purine nucleoside phosphorylase. 1. Structure-function studies."
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:16930574
  qualifier: enables
  review:
    summary: >-
      PNP enzymatic activity assayed in the enzyme-replacement study; supports the
      core molecular function.
    action: ACCEPT
    reason: >-
      Intracellular PNP activity is measured/restored in PNP-deficient lymphocytes,
      confirming the enzyme's phosphorylase activity.
    supported_by:
    - reference_id: PMID:16930574
      supporting_text: "Purine nucleoside phosphorylase (PNP) is an intracellular enzyme crucial for"
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:18938130
  qualifier: enables
  review:
    summary: >-
      PNP enzymatic activity measured by ITC-based assay; supports the core MF.
    action: ACCEPT
    reason: >-
      The study assays human PNP enzymatic activity (7-methylguanosine + phosphate),
      confirming phosphorylase activity.
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:3029074
  qualifier: enables
  review:
    summary: >-
      PNP catalytic activity (and its loss in the E89K deficiency variant) directly
      demonstrated; supports the core MF.
    action: ACCEPT
    reason: >-
      Reversion of the single-base E89K mutation restores PNP catalytic activity,
      directly linking the gene product to phosphorylase activity.
    supported_by:
    - reference_id: PMID:3029074
      supporting_text: "This single base mutation alters the codon at position 89 from Glu to Lys, a"
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:9305962
  qualifier: enables
  review:
    summary: >-
      Steady-state kinetics of human PNP and active-site mutants; core MF.
    action: ACCEPT
    reason: >-
      Structure-function/mutagenesis study directly characterizes the phosphorylase
      activity of human PNP.
    supported_by:
    - reference_id: PMID:9305962
      supporting_text: "Purine nucleoside phosphorylase. 1. Structure-function studies."
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:16930574
  qualifier: located_in
  review:
    summary: >-
      Direct evidence that PNP is predominantly cytoplasmic; consistent with the
      cytosol annotations.
    action: ACCEPT
    reason: >-
      Endogenous and delivered PNP are predominantly distributed in the cytoplasm,
      supporting the cytoplasm/cytosol localization.
    supported_by:
    - reference_id: PMID:16930574
      supporting_text: "distributed in the cytoplasm"
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: IDA
  original_reference_id: PMID:3029074
  qualifier: located_in
  review:
    summary: >-
      Cytoplasmic localization of PNP; consistent with cytosolic function.
    action: ACCEPT
    reason: >-
      Consistent with the curated cytoplasm/cytosol location of the enzyme.
- term:
    id: GO:0006139
    label: nucleobase-containing compound metabolic process
  evidence_type: IDA
  original_reference_id: PMID:3029074
  qualifier: involved_in
  review:
    summary: >-
      Very broad "nucleobase-containing compound metabolic process"; correct but far
      less informative than the specific purine catabolic/salvage terms.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      This high-level parent term is subsumed by the specific inosine/guanosine
      (deoxy)nucleoside catabolic and purine salvage terms already annotated.
- term:
    id: GO:0006738
    label: nicotinamide riboside catabolic process
  evidence_type: IDA
  original_reference_id: PMID:19001417
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses nicotinamide riboside to nicotinamide, a genuine
      alternative-substrate activity feeding NAD+ salvage.
    action: ACCEPT
    reason: >-
      Mammalian PNP (not MTAP) is responsible for kinase-independent NR utilization,
      cleaving NR to nicotinamide; directly demonstrated in mammalian extracts and by
      Immucillin-H (PNP-specific inhibitor) sensitivity.
    supported_by:
    - reference_id: PMID:19001417
      supporting_text: "that mammalian purine nucleoside phosphorylase but not methylthioadenosine"
- term:
    id: GO:0006955
    label: immune response
  evidence_type: IMP
  original_reference_id: PMID:16930574
  qualifier: involved_in
  review:
    summary: >-
      PNP is required for normal T-cell immune function; its deficiency causes T-cell
      immunodeficiency. Indirect, downstream physiological role.
    action: KEEP_AS_NON_CORE
    reason: >-
      "Immune response" is a broad downstream consequence of PNP's metabolic role
      (dGTP toxicity to T lymphocytes on loss of function); enzyme replacement in
      PNP-deficient T cells corrects their function. Not a core molecular function.
    supported_by:
    - reference_id: PMID:16930574
      supporting_text: "functions of PNP-deficient T lymphocytes including their response to stimulation"
- term:
    id: GO:0009410
    label: response to xenobiotic stimulus
  evidence_type: IMP
  original_reference_id: PMID:15047506
  qualifier: involved_in
  review:
    summary: >-
      PNP phosphorolyses the antiviral prodrug 2',3'-dideoxyinosine (ddI), a
      drug/xenobiotic-metabolism role.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP-dependent breakdown of the xenobiotic ddI is a pharmacologically relevant
      but peripheral activity reflecting its broad nucleoside-phosphorolysis
      chemistry, not a core physiological process.
    supported_by:
    - reference_id: PMID:15047506
      supporting_text: "A metabolic route for ddI clearance is its breakdown by purine nucleoside"
- term:
    id: GO:0042301
    label: phosphate ion binding
  evidence_type: IDA
  original_reference_id: PMID:18938130
  qualifier: enables
  review:
    summary: >-
      PNP binds inorganic phosphate, the co-substrate/nucleophile of phosphorolysis,
      in a dedicated phosphate-binding site; supporting MF.
    action: ACCEPT
    reason: >-
      Phosphate is the second substrate of the phosphorolysis reaction and binds a
      defined active-site pocket; phosphate binding is integral to catalysis and
      modulates inhibitor binding.
    supported_by:
    - reference_id: PMID:18938130
      supporting_text: "Effect of the phosphate substrate on drug-inhibitor binding to human purine"
- term:
    id: GO:0034418
    label: urate biosynthetic process
  evidence_type: IDA
  original_reference_id: PMID:16964310
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      PNP acts upstream in urate production (PNP -> hypoxanthine -> xanthine
      oxidase -> urate); an indirect downstream pathway role.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP generates hypoxanthine, the substrate for downstream oxidation to urate by
      xanthine oxidoreductase; PNP does not itself synthesize urate, so this is a
      pathway-level (acts_upstream_of_or_within) annotation.
- term:
    id: GO:0042102
    label: positive regulation of T cell proliferation
  evidence_type: IDA
  original_reference_id: PMID:16964310
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      Restoring PNP in PNP-deficient mice corrects T-cell immunity; an indirect
      downstream immunological consequence.
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP is not a direct regulator of T-cell proliferation; its loss causes
      dGTP-mediated T-cell toxicity, and enzyme replacement (TAT-PNP) rescues immune
      function in PNP-deficient mice. Physiological consequence, not core function.
    supported_by:
    - reference_id: PMID:16964310
      supporting_text: "severe T cell immunodeficiency, neurological"
- term:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  evidence_type: IDA
  original_reference_id: PMID:16964310
  qualifier: enables
  review:
    summary: >-
      PNP catalytic activity assayed/restored in the mouse enzyme-replacement study;
      supports the core MF.
    action: ACCEPT
    reason: >-
      TAT-PNP delivery restores PNP enzymatic activity in PNP-deficient tissues,
      confirming the phosphorylase activity of the enzyme.
    supported_by:
    - reference_id: PMID:16964310
      supporting_text: "severe T cell immunodeficiency, neurological"
- term:
    id: GO:0006148
    label: inosine catabolic process
  evidence_type: IDA
  original_reference_id: PMID:16964310
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      PNP catabolizes inosine; restoring the activity corrects nucleoside
      homeostasis in PNP-deficient mice. Core catabolic role.
    action: ACCEPT
    reason: >-
      Correction of abnormal nucleoside homeostasis on PNP replacement is consistent
      with PNP's core inosine-catabolic function.
    supported_by:
    - reference_id: PMID:16964310
      supporting_text: "abnormal nucleoside homeostasis, severe T cell immunodeficiency, neurological"
- term:
    id: GO:0046638
    label: positive regulation of alpha-beta T cell differentiation
  evidence_type: IDA
  original_reference_id: PMID:16964310
  qualifier: acts_upstream_of_or_within
  review:
    summary: >-
      Indirect downstream immunological consequence of PNP activity (T-cell
      development/function rescued by enzyme replacement).
    action: KEEP_AS_NON_CORE
    reason: >-
      PNP does not directly regulate alpha-beta T-cell differentiation; the phenotype
      reflects relief of dGTP toxicity to developing/activated T cells upon restoring
      enzyme activity. Non-core physiological consequence.
    supported_by:
    - reference_id: PMID:16964310
      supporting_text: "severe T cell immunodeficiency, neurological"
core_functions:
- description: >-
    Phosphorolytic cleavage of the N-glycosidic bond of 6-oxopurine
    (deoxy)ribonucleosides (inosine, guanosine, 2'-deoxyinosine, 2'-deoxyguanosine),
    using inorganic phosphate to produce the free purine base (hypoxanthine or
    guanine) plus (2'-deoxy)-alpha-D-ribose-1-phosphate.
  molecular_function:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  directly_involved_in:
  - id: GO:0006148
    label: inosine catabolic process
  supported_by:
  - reference_id: PMID:6771276
    supporting_text: "the phosphorolysis of inosine, deoxyinosine, guanosine, and deoxyguanosine with"
  - reference_id: PMID:23438750
    supporting_text: "catalyzes the reversible phosphorolysis of purine (deoxy)-ribonucleosides to the corresponding purine base"
- description: >-
    Generation of free purine bases (hypoxanthine, guanine) from purine nucleosides,
    supplying the purine salvage pathway; the reversible reaction also contributes to
    nucleoside interconversion in purine-containing compound salvage.
  molecular_function:
    id: GO:0004731
    label: purine-nucleoside phosphorylase activity
  directly_involved_in:
  - id: GO:0043101
    label: purine-containing compound salvage
  locations:
  - id: GO:0005829
    label: cytosol
  supported_by:
  - reference_id: PMID:9305964
    supporting_text: "highly specific for 6-oxopurine"
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: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:0000052
  title: Gene Ontology annotation based on curation of immunofluorescence data
  findings: []
- id: GO_REF:0000116
  title: Automatic Gene Ontology annotation based on Rhea mapping
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:15047506
  title: Role of purine nucleoside phosphorylase in interactions between 2',3'-dideoxyinosine
    and allopurinol, ganciclovir, or tenofovir.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Full text cached; establishes PNP-dependent phosphorolysis/clearance of the
      antiviral ddI, supporting the response-to-xenobiotic annotation.
- id: PMID:16930574
  title: Intracellular delivery of purine nucleoside phosphorylase (PNP) fused to
    protein transduction domain corrects PNP deficiency in vitro.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Enzyme-replacement study confirming PNP activity, cytoplasmic localization, and
      correction of T-lymphocyte function/IL-2 in PNP-deficient cells.
- id: PMID:16964310
  title: TAT-mediated intracellular delivery of purine nucleoside phosphorylase corrects
    its deficiency in mice.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      In vivo mouse enzyme replacement; ties PNP activity to correction of nucleoside
      homeostasis and T-cell immunodeficiency (downstream immune/urate annotations).
- id: PMID:18938130
  title: Effect of the phosphate substrate on drug-inhibitor binding to human purine
    nucleoside phosphorylase.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      ITC study of human PNP; supports phosphate-ion binding and enzymatic activity;
      confirms trimer with catalytic sites at subunit interfaces.
- id: PMID:19001417
  title: Nicotinamide riboside and nicotinic acid riboside salvage in fungi and mammals.
    Quantitative basis for Urh1 and purine nucleoside phosphorylase function in NAD+
    metabolism.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Full text cached; demonstrates mammalian PNP (not MTAP) as the NR phosphorylase
      feeding NAD+ salvage; supports NR catabolism annotation.
- id: PMID:19056867
  title: Large-scale proteomics and phosphoproteomics of urinary exosomes.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      High-throughput exosome proteomics; supports incidental exosome detection, not
      a functional localization.
- id: PMID:20212140
  title: Four generations of transition-state analogues for human purine nucleoside
    phosphorylase.
  findings: []
  reference_review:
    relevance: MEDIUM
    correctness: VERIFIED
    review_notes: >-
      Structural study of human PNP transition-state analogue inhibitors; used here
      as an IntAct self-interaction source consistent with the homotrimer.
- id: PMID:20458337
  title: MHC class II-associated proteins in B-cell exosomes and potential functional
    implications for exosome biogenesis.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      High-throughput exosome proteomics; incidental detection of a cytosolic enzyme.
- id: PMID:23438750
  title: Catalytic site conformations in human PNP by 19F-NMR and crystallography.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Full text cached; establishes reversible phosphorolysis of purine
      (deoxy)ribonucleosides, homotrimeric structure, and catalytic mechanism.
- 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: >-
      High-throughput exosome proteomics; incidental detection.
- id: PMID:25502805
  title: A massively parallel pipeline to clone DNA variants and examine molecular
    phenotypes of human disease mutations.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Large-scale variant/interaction pipeline; used as an IntAct self-interaction
      source consistent with the homotrimer.
- id: PMID:31515488
  title: Extensive disruption of protein interactions by genetic variants across the
    allele frequency spectrum in human populations.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Large-scale interactome-perturbation study; IntAct self-interaction source.
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Binary interactome map (HuRI); IntAct self-interaction source consistent with
      homotrimer.
- id: PMID:32814053
  title: Interactome Mapping Provides a Network of Neurodegenerative Disease Proteins
    and Uncovers Widespread Protein Aggregation in Affected Brains.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Y2H neurodegenerative-disease interactome; source of non-specific protein
      binding IPIs flagged as over-annotation.
- id: PMID:3029074
  title: A human purine nucleoside phosphorylase deficiency caused by a single base
    change.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Identifies the E89K deficiency mutation abolishing PNP activity; supports
      catalytic activity, cytoplasmic localization, and PNP-deficiency biology.
- id: PMID:5056638
  title: Purine nucleoside phosphorylase activity of human erythrocytes in iron deficiency
    anaemia.
  findings: []
  reference_review:
    relevance: LOW
    correctness: VERIFIED
    review_notes: >-
      Abstract-only cache; human erythrocyte PNP activity assay supporting the
      catalytic-activity annotation.
- id: PMID:6771276
  title: Characterization of purine nucleoside phosphorylase from human granulocytes
    and its metabolism of deoxyribonucleosides.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Key experimental characterization: purified human PNP is a trimer and
      phosphorolyses inosine, deoxyinosine, guanosine and deoxyguanosine; adenine and
      pyrimidine (deoxy)nucleosides are not substrates.
- id: PMID:9305962
  title: Purine nucleoside phosphorylase. 1. Structure-function studies.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Active-site mutagenesis (Asn243, Glu201, His86) defining substrate/base binding
      and catalysis; supports nucleoside and purine-nucleobase binding.
- id: PMID:9305964
  title: Purine nucleoside phosphorylase. 3. Reversal of purine base specificity by
    site-directed mutagenesis.
  findings: []
  reference_review:
    relevance: HIGH
    correctness: VERIFIED
    review_notes: >-
      Establishes 6-oxopurine specificity (inosine kcat/KM ~350,000-fold over
      adenosine) and kinetic parameters; N243D reverses specificity to 6-aminopurines.
- id: Reactome:R-HSA-112033
  title: PNP catalyzes the conversion of hypoxanthine and (deoxy)ribose-1-phosphate
    to (deoxy)inosine
  findings: []
- id: Reactome:R-HSA-112034
  title: PNP catalyzes the conversion of guanine and (deoxy)ribose-1-phosphate to
    (deoxy)guanosine
  findings: []
- id: Reactome:R-HSA-6798748
  title: Exocytosis of secretory granule lumen proteins
  findings: []
- id: Reactome:R-HSA-6800434
  title: Exocytosis of ficolin-rich granule lumen proteins
  findings: []
- id: Reactome:R-HSA-74242
  title: PNP catalyzes the conversion of (deoxy)inosine to hypoxanthine and (deoxy)ribose
  findings: []
- id: Reactome:R-HSA-74249
  title: PNP catalyzes the conversion of (deoxy)guanosine to guanine and (deoxy)ribose
  findings: []
- id: Reactome:R-HSA-9735775
  title: Defective PNP does not convert (deoxy)inosine to hypoxanthine and (deoxy)ribose
  findings: []
- id: Reactome:R-HSA-9735789
  title: Defective PNP does not convert (deoxy)guanosine to guanine and (deoxy)ribose
  findings: []
- id: Reactome:R-HSA-9755044
  title: PNP trimer transforms RBV to T-CONH2
  findings: []