APRT

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0003999 adenine phosphoribosyltransferase activity	IBA GO_REF:0000033	ACCEPT	Summary: Core molecular function of APRT - transfer of the phosphoribosyl group of PRPP to adenine to form AMP (EC 2.4.2.7). Phylogenetically inferred and consistent with direct enzymatic and structural evidence for the human enzyme. Reason: This is the defining catalytic activity of APRT, supported by the crystal structure with AMP product and measured kinetics for the human enzyme, and conserved across the phosphoribosyltransferase family used for the IBA inference. Supporting Evidence: PMID:15196008 In mammals, adenine phosphoribosyltransferase (APRT, EC 2.4.2.7) is present in all tissues and provides the only known mechanism for the metabolic salvage of adenine
GO:0005737 cytoplasm	IBA GO_REF:0000033	ACCEPT	Summary: APRT is a soluble cytoplasmic/cytosolic enzyme; phylogenetic inference of a cytoplasmic location is correct but less precise than the cytosol annotations. Reason: Consistent with the UniProt subcellular location (Cytoplasm) and with the more specific cytosol annotations from HPA and Ensembl. Correct as a broader location term. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0006168 adenine salvage	IBA GO_REF:0000033	ACCEPT	Summary: APRT is the enzyme that salvages free adenine by converting it to AMP; adenine salvage is a core biological process for this gene. Reason: Directly matches the established function - APRT provides the salvage route for adenine arising from polyamine biosynthesis and diet. Well supported experimentally and by phylogeny. Supporting Evidence: PMID:15196008 provides the only known mechanism for the metabolic salvage of adenine resulting from the polyamine biosynthesis pathway or from dietary sources
GO:0044209 AMP salvage	IBA GO_REF:0000033	ACCEPT	Summary: The product of the APRT reaction is AMP; the enzyme constitutes the AMP-from-adenine salvage step. Core biological process. Reason: UniProt records the pathway explicitly as AMP biosynthesis via salvage pathway (AMP from adenine, step 1/1), matching this term. Consistent with the IBA inference. Supporting Evidence: file:human/APRT/APRT-uniprot.txt PATHWAY: Purine metabolism; AMP biosynthesis via salvage pathway; AMP from adenine: step 1/1.
GO:0002055 adenine binding	IBA GO_REF:0000033	ACCEPT	Summary: Adenine is the small-molecule substrate of APRT; binding of adenine is a mechanistic component of the catalytic function. Reason: Supported by the human structure/kinetics (KM for adenine ~4 uM) and consistent with the enzyme's substrate specificity. A valid, informative substrate-binding term underpinning the catalytic activity. Supporting Evidence: file:human/APRT/APRT-uniprot.txt KM=4 uM for adenine
GO:0016208 AMP binding	IBA GO_REF:0000033	ACCEPT	Summary: AMP is the reaction product of APRT and is co-crystallized in the active site; product binding is a mechanistic component of catalysis. Reason: The human enzyme was crystallized in complex with AMP, directly demonstrating AMP binding in the active-site pocket. Consistent with the IBA inference. Supporting Evidence: PMID:15196008 the recombinant human APRT was crystallized in complex with adenosine 5'-monophosphate (AMP)
GO:0003999 adenine phosphoribosyltransferase activity	IEA GO_REF:0000120	ACCEPT	Summary: Electronic assertion (UniProt combined pipeline; RHEA:16609 / EC 2.4.2.7) of the core catalytic activity, in agreement with the experimental annotation. Reason: Correct and specific; duplicates the experimentally supported core molecular function. Retained as a valid electronic corroboration. Supporting Evidence: file:human/APRT/APRT-uniprot.txt EC=2.4.2.7 {ECO:0000269\|PubMed:15196008}
GO:0005737 cytoplasm	IEA GO_REF:0000120	ACCEPT	Summary: Electronic assertion of cytoplasmic localization (UniProt-SubCell SL-0086), consistent with the curated subcellular location. Reason: Matches the UniProt cytoplasm subcellular location and the more specific cytosol annotations. Correct broader location. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0006168 adenine salvage	IEA GO_REF:0000002	ACCEPT	Summary: InterPro2GO electronic assertion (IPR005764, adenine phosphoribosyltransferase) of adenine salvage, matching the core biological process. Reason: Correct process term derived from the family-specific InterPro signature; duplicates the experimentally/phylogenetically supported adenine salvage role. Supporting Evidence: PMID:15196008 provides the only known mechanism for the metabolic salvage of adenine
GO:1901363 heterocyclic compound binding	IEA GO_REF:0000117	MARK AS OVER ANNOTATED	Summary: Very general ARBA-derived binding term. APRT does bind heterocyclic compounds (adenine, AMP), but this high-level term is uninformative relative to the specific adenine binding / AMP binding annotations already present. Reason: The term is not incorrect (adenine and AMP are heterocyclic), but it is an overly generic parent term that adds no functional information beyond the specific substrate/product binding terms; per curation guidelines uninformative high-level binding terms should not be treated as representing gene function. Supporting Evidence: file:human/APRT/APRT-uniprot.txt KM=4 uM for adenine
GO:0005515 protein binding	IPI PMID:32296183 A reference map of the human binary protein interactome.	MARK AS OVER ANNOTATED	Summary: High-throughput binary interactome (HuRI) IPI annotation; the interaction partner is TTC19 (UniProtKB:Q6DKK2). "protein binding" is an uninformative molecular function term and no specific adaptor/complex role for APRT is established. Reason: This is an experimentally derived interaction, so it is retained rather than removed, but bare "protein binding" conveys no specific molecular function and the TTC19 interaction has no established functional consequence for adenine salvage; it should not be treated as a core function. Supporting Evidence: PMID:32296183 reference interactome map of human binary protein interactions
GO:0005515 protein binding	IPI PMID:32814053 Interactome Mapping Provides a Network of Neurodegenerative ...	MARK AS OVER ANNOTATED	Summary: Yeast two-hybrid interactome (neurodegenerative-disease network) IPI annotation; the partner is SPRED1 (UniProtKB:Q7Z699). Bare "protein binding" is uninformative and no specific functional role is defined. Reason: Retained as an experimental interaction but the generic "protein binding" term adds no functional specificity for APRT and the interaction has no established biological consequence for its salvage function; not a core function. Supporting Evidence: PMID:32814053 systematic yeast two-hybrid interaction screening
GO:0002055 adenine binding	IEA GO_REF:0000107	ACCEPT	Summary: Ensembl-Compara ortholog-transfer (from mouse Aprt, P08030) of adenine binding, matching the enzyme's substrate. Reason: Correct substrate-binding term consistent with the IBA/experimental adenine binding evidence; duplicates a valid mechanistic MF component. Supporting Evidence: file:human/APRT/APRT-uniprot.txt KM=4 uM for adenine
GO:0005829 cytosol	IEA GO_REF:0000107	ACCEPT	Summary: Ensembl-Compara ortholog-transfer of cytosolic localization; APRT is a soluble cytosolic enzyme. Reason: Consistent with the IDA (HPA) cytosol annotation and the UniProt cytoplasmic location. Correct and specific. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0032263 GMP salvage	IEA GO_REF:0000107	REMOVE	Summary: Ensembl-Compara ortholog-transferred process annotation. APRT is specific for adenine and produces AMP; it does not act on guanine and has no role in GMP salvage (that is the function of HGPRT/HPRT1). Reason: Incorrect electronic (IEA) inference. The APRT reaction (adenine + PRPP -> AMP) does not generate or salvage GMP; GMP/guanine salvage is carried out by hypoxanthine-guanine phosphoribosyltransferase, a different enzyme. This appears to be an over-broad process transfer across the PRTase family and is biologically wrong for APRT. Supporting Evidence: file:human/APRT/APRT-uniprot.txt PATHWAY: Purine metabolism; AMP biosynthesis via salvage pathway; AMP from adenine: step 1/1.
GO:0032264 IMP salvage	IEA GO_REF:0000107	REMOVE	Summary: Ensembl-Compara ortholog-transferred process annotation. APRT is adenine-specific and produces AMP; it does not act on hypoxanthine and has no role in IMP salvage (that is the function of HGPRT/HPRT1). Reason: Incorrect electronic (IEA) inference. The APRT reaction produces AMP from adenine, not IMP from hypoxanthine; IMP/hypoxanthine salvage is carried out by hypoxanthine-guanine phosphoribosyltransferase. Biologically wrong for APRT and an over-broad family-level process transfer. Supporting Evidence: file:human/APRT/APRT-uniprot.txt PATHWAY: Purine metabolism; AMP biosynthesis via salvage pathway; AMP from adenine: step 1/1.
GO:0044209 AMP salvage	IEA GO_REF:0000120	ACCEPT	Summary: UniProt combined-pipeline electronic assertion (UniPathway UPA00588) of AMP salvage, matching the core biological process. Reason: Correct and specific; duplicates the phylogenetically supported AMP salvage role and agrees with the UniProt AMP-from-adenine salvage pathway assignment. Supporting Evidence: file:human/APRT/APRT-uniprot.txt PATHWAY: Purine metabolism; AMP biosynthesis via salvage pathway; AMP from adenine: step 1/1.
GO:0005829 cytosol	IDA GO_REF:0000052	ACCEPT	Summary: Direct immunofluorescence localization (Human Protein Atlas) to the cytosol, the site of APRT catalytic activity. Reason: Experimental (IDA) support for the correct, specific subcellular location of this soluble salvage enzyme; consistent with UniProt. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0003999 adenine phosphoribosyltransferase activity	IDA PMID:15196008 Three-dimensional structure of human adenine phosphoribosylt...	ACCEPT	Summary: Direct experimental determination of the catalytic activity of the recombinant human enzyme, including the crystal structure and kinetic parameters; this is the core molecular function. Reason: Strongest evidence for the defining function of APRT - direct assay of adenine phosphoribosyltransferase (EC 2.4.2.7) activity on the human protein. Supporting Evidence: PMID:15196008 In mammals, adenine phosphoribosyltransferase (APRT, EC 2.4.2.7) is present in all tissues and provides the only known mechanism for the metabolic salvage of adenine
GO:0005829 cytosol	TAS Reactome:R-HSA-9734193	ACCEPT	Summary: Reactome traceable assertion (Defective APRT does not convert adenine to AMP) placing APRT in the cytosol, the site of the salvage reaction. Reason: Correct and specific location, consistent with the experimental (IDA) cytosol annotation and UniProt. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0005576 extracellular region	TAS Reactome:R-HSA-6798748	MARK AS OVER ANNOTATED	Summary: Reactome annotation derived from the neutrophil-degranulation pathway (Exocytosis of secretory granule lumen proteins). APRT is detected in neutrophil granule proteomes but this is not its site of catalytic function. Reason: APRT is a cytosolic salvage enzyme with no signal peptide and no secretory function; its appearance in the extracellular region reflects inclusion in a large neutrophil-degranulation proteome pathway rather than a genuine functional extracellular localization. Retained (not a demonstrably wrong IEA) but flagged as over-annotation. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0034774 secretory granule lumen	TAS Reactome:R-HSA-6798748	MARK AS OVER ANNOTATED	Summary: Reactome annotation from the neutrophil-degranulation pathway. Reflects detection of APRT in neutrophil granule preparations, not a bona fide functional localization of this cytosolic enzyme. Reason: As with the extracellular-region annotation, this is a consequence of APRT being catalogued in a neutrophil secretory-granule proteome pathway. APRT is a soluble cytosolic protein without a secretory route; not a core location. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0070062 extracellular exosome	HDA PMID:23533145 In-depth proteomic analyses of exosomes isolated from expres...	MARK AS OVER ANNOTATED	Summary: High-throughput proteomic detection of APRT in urinary/prostatic exosome preparations. A common finding for abundant cytosolic proteins; not a functional localization. Reason: Detection in a large exosome proteome (~900 proteins) reflects the well-known presence of abundant cytosolic enzymes in extracellular vesicle preparations rather than a specific functional role of APRT in exosomes. Retained as experimental but flagged as over-annotation. Supporting Evidence: PMID:23533145 exosome preparations were characterized by a shotgun proteomics procedure
GO:0070062 extracellular exosome	HDA PMID:19056867 Large-scale proteomics and phosphoproteomics of urinary exos...	MARK AS OVER ANNOTATED	Summary: High-throughput proteomic detection of APRT among 1132 proteins profiled in human urinary exosomes; a mass-spectrometry catalogue rather than evidence of functional exosomal localization. Reason: The same over-annotation pattern - abundant cytosolic APRT is captured in large-scale urinary exosome proteomes. Not a core or functional location for this salvage enzyme. Supporting Evidence: PMID:19056867 we used LC-MS/MS to profile the proteome of human urinary exosomes
GO:0070062 extracellular exosome	HDA PMID:20458337 MHC class II-associated proteins in B-cell exosomes and pote...	MARK AS OVER ANNOTATED	Summary: High-throughput proteomic detection of APRT in the total proteome of purified B-cell-derived exosomes (539 proteins); a proteomic catalogue, not functional localization. Reason: Third instance of the exosome-proteome over-annotation pattern. APRT is an abundant cytosolic enzyme routinely recovered in extracellular-vesicle preparations; this is not a core location. Supporting Evidence: PMID:20458337 total proteome of highly purified B cell-derived exosomes
GO:0005829 cytosol	TAS Reactome:R-HSA-74213	ACCEPT	Summary: Reactome traceable assertion (APRT catalyzes the conversion of adenine to AMP) placing the reaction in the cytosol, the correct functional location. Reason: Correct and specific; consistent with the experimental cytosol annotation and UniProt cytoplasmic location, and it correctly assigns the catalytic reaction to the cytosol. Supporting Evidence: file:human/APRT/APRT-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm.
GO:0016208 AMP binding	IDA PMID:15196008 Three-dimensional structure of human adenine phosphoribosylt...	ACCEPT	Summary: Direct structural evidence of AMP binding - the human enzyme was crystallized in complex with its AMP product occupying the active-site pocket. Reason: Experimental (IDA) support for product binding, a mechanistic component of the catalytic function; the co-crystal structure with AMP directly demonstrates binding. Supporting Evidence: PMID:15196008 the active site pocket opens slightly to accommodate the AMP product
GO:0005737 cytoplasm	TAS PMID:16130169 Proteomics of human umbilical vein endothelial cells applied...	ACCEPT	Summary: Cytoplasmic localization asserted from a HUVEC proteomic study. Consistent with the soluble cytoplasmic nature of APRT, though less specific than the cytosol annotations. Reason: Correct broader location term, in agreement with UniProt and the cytosol annotations. The supporting proteomic study catalogued cytoplasmic endothelial proteins including APRT. Supporting Evidence: PMID:16130169 The overall functional characterization of the 162 identified proteins
GO:0003999 adenine phosphoribosyltransferase activity	TAS PMID:3531209 Human adenine phosphoribosyltransferase. Complete amino acid...	ACCEPT	Summary: Traceable assertion of the core adenine phosphoribosyltransferase function, from the paper that established the complete amino acid sequence of the human erythrocyte enzyme. Reason: Supports the defining catalytic function of APRT; the reference characterizes the human enzyme and its family relationship to other phosphoribosyltransferases. Supporting Evidence: PMID:3531209 Human adenine phosphoribosyltransferase has sequence homology with xanthine-guanine phosphoribosyltransferase from Escherichia coli

Gene Description

Existing Annotations Review

Core Functions

Catalyzes the salvage of free adenine by transferring the phosphoribosyl group of PRPP to adenine, producing AMP and diphosphate (EC 2.4.2.7), in the cytosol.

Recycles adenine into the adenine nucleotide pool by producing AMP, constituting the AMP-from-adenine salvage step of purine metabolism.

References

📚 Additional Documentation

Notes

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