hpt1 (SPAC23C11.13c; UniProt O13917) encodes hypoxanthine-guanine(-xanthine) phosphoribosyltransferase (EC 2.4.2.8). This single PRPP-dependent enzyme salvages hypoxanthine, guanine and xanthine to IMP, GMP and XMP: one 8-azathioxanthine-resistance mutation removes all three activities together. Mutants lacking guanine PRTase (pur1) also take up guanine more slowly. The enzyme is assigned to the cytosol by curator inference.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0000310 xanthine phosphoribosyltransferase activity | IDA PMID:5123876 The substrate specificity of purine phosphoribosyltransferas... | ACCEPT | Summary: A single mutation removes hypoxanthine, xanthine and guanine PRTase activities together, so one enzyme carries all three. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0004422 hypoxanthine phosphoribosyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference; consistent. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0004422 hypoxanthine phosphoribosyltransferase activity | IDA PMID:5123876 The substrate specificity of purine phosphoribosyltransferas... | ACCEPT | Summary: HGPRT activity lost in an 8-azathioxanthine-resistant mutant. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0004422 hypoxanthine phosphoribosyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC/RHEA mapping; consistent. Reason: S. pombe hypoxanthine PRTase activity is lost in an 8-azathioxanthine-resistant single mutant together with the guanine and xanthine PRTase activities (PMID:5123876, the source of the separate IDA row, cited as corroboration of this mapping); UniProt records the IMP-forming reaction (by similarity to UniProtKB:Q04178) and PANTHER places the protein in the HGPRT subfamily. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. file:SCHPO/hpt1/hpt1-uniprot.txt Reaction=IMP + diphosphate = hypoxanthine + 5-phospho-alpha-D-ribose 1- file:SCHPO/hpt1/hpt1-uniprot.txt PTHR43363:SF1; HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE |
| GO:0005634 nucleus | ISO GO_REF:0000024 | KEEP AS NON CORE | Summary: Transfer of nuclear location from S. cerevisiae HPT1; screen-based. Reason: Not part of the core function. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005783 endoplasmic reticulum | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt location mapping to ER; no supporting evidence for an ER-resident PRTase. Reason: Not supported. Supporting Evidence: PMID:16823372 we determined the localization of 4,431 proteins |
| GO:0005829 cytosol | IC GO_REF:0000111 | ACCEPT | Summary: Curator inference of cytosol for this soluble purine salvage enzyme. Reason: No direct cytosol observation is available for S. pombe Hpt1. The inference rests on family membership (purine/pyrimidine phosphoribosyltransferase family, PANTHER HGPRT subfamily, whose members are soluble cytosolic salvage enzymes) and on the absence of any targeting or membrane feature: the record's FT section has only CHAIN, ACT_SITE and BINDING features (no SIGNAL, TRANSIT or TRANSMEM). The only S. pombe location data, the ORFeome screen behind UniProt's ER location (PMID:16823372), conflict with this and are reviewed on the ER row; the cytosol call should be confirmed experimentally. Supporting Evidence: file:SCHPO/hpt1/hpt1-uniprot.txt SIMILARITY: Belongs to the purine/pyrimidine phosphoribosyltransferase file:SCHPO/hpt1/hpt1-uniprot.txt PTHR43363:SF1; HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE |
| GO:0006166 purine ribonucleoside salvage | ISO GO_REF:0000024 | KEEP AS NON CORE | Summary: Transfer from human HPRT1; HGPRT salvages bases to nucleotides. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0009168 purine ribonucleoside monophosphate biosynthetic process | IEA GO_REF:0000117 | MODIFY | Summary: Broad ARBA parent; correct but general, refined to the three specific salvage processes the gene carries. Reason: Action changed from KEEP_AS_NON_CORE, whose reason argued only that the term is broad. Purine ribonucleoside monophosphate biosynthetic process is correct, but the gene already carries a specific descendant for each base it salvages, and a term that is correct but general is refined to all supported descendants rather than kept as their common ancestor. An S. pombe mutant study (PMID:5123876) shows that one locus supplies the hypoxanthine, xanthine and guanine phosphoribosyltransferase activities, and the curated function (by similarity) places the enzyme in purine nucleotide salvage. Replacements are GO:0032264 IMP salvage, GO:0032263 GMP salvage and GO:0032265 XMP salvage. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. file:SCHPO/hpt1/hpt1-uniprot.txt Converts guanine to guanosine monophosphate, and hypoxanthine to inosine monophosphate. file:SCHPO/hpt1/hpt1-uniprot.txt Plays a central role in the generation of purine nucleotides through the purine salvage pathway (By similarity). |
| GO:0016763 pentosyltransferase activity | IMP PMID:14008 Study of the role of puring phosphoribosyltransferases in th... | MODIFY | Summary: pur1 mutants lacking guanine PRTase take up guanine more slowly; the specific activity is guanine phosphoribosyltransferase. Reason: Too general. Proposed replacements: guanine phosphoribosyltransferase activity Supporting Evidence: PMID:14008 pur 1, devoid of guanine phosphoribosyltransferase activity have a lowered uptake rate of adenine and guanine respectively |
| GO:0032263 GMP salvage | EXP PMID:5123876 The substrate specificity of purine phosphoribosyltransferas... | ACCEPT | Summary: Guanine PRTase activity makes GMP (substrate specificity study). Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0032263 GMP salvage | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference; consistent. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0032263 GMP salvage | IDA PMID:20306 Purification and comparative study of adenine and guanine ph... | ACCEPT | Summary: Guanine PRTase purified (curator, full text). Supporting Evidence: PMID:20306 Purification and comparative study of adenine and guanine phosphoribosyltransferases |
| GO:0032264 IMP salvage | EXP PMID:5123876 The substrate specificity of purine phosphoribosyltransferas... | ACCEPT | Summary: Hypoxanthine PRTase activity makes IMP. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0032264 IMP salvage | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference; consistent. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0032265 XMP salvage | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference; xanthine PRTase activity makes XMP. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0046100 hypoxanthine metabolic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Broad parent. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0052657 guanine phosphoribosyltransferase activity | IDA PMID:20306 Purification and comparative study of adenine and guanine ph... | ACCEPT | Summary: Guanine PRTase purified (curator, full text). Supporting Evidence: PMID:20306 Purification and comparative study of adenine and guanine phosphoribosyltransferases |
| GO:0052657 guanine phosphoribosyltransferase activity | IDA PMID:5123876 The substrate specificity of purine phosphoribosyltransferas... | ACCEPT | Summary: Guanine PRTase activity lost with the HGXPRT mutation. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. |
| GO:0052657 guanine phosphoribosyltransferase activity | IEA GO_REF:0000116 | ACCEPT | Summary: RHEA mapping; consistent. Reason: Guanine PRTase activity is lost in the same S. pombe single mutant that lacks hypoxanthine and xanthine PRTase activities (PMID:5123876, source of a separate IDA row, cited as corroboration of this mapping); UniProt records the GMP-forming reaction by similarity to UniProtKB:Q04178. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. file:SCHPO/hpt1/hpt1-uniprot.txt Reaction=GMP + diphosphate = guanine + 5-phospho-alpha-D-ribose 1- file:SCHPO/hpt1/hpt1-uniprot.txt PTHR43363:SF1; HYPOXANTHINE-GUANINE PHOSPHORIBOSYLTRANSFERASE |
| GO:0106380 purine ribonucleotide salvage | IEA GO_REF:0000117 | MODIFY | Summary: Broad ARBA parent; correct but general, refined to the three specific salvage processes the gene carries. Reason: Action changed from KEEP_AS_NON_CORE, whose reason argued only that the term is broad. Purine ribonucleotide salvage is correct, but the gene already carries a specific descendant for each base it salvages, and a term that is correct but general is refined to all supported descendants rather than kept as their common ancestor. An S. pombe mutant study (PMID:5123876) shows that one locus supplies the hypoxanthine, xanthine and guanine phosphoribosyltransferase activities, and the curated function (by similarity) places the enzyme in purine nucleotide salvage. Replacements are GO:0032264 IMP salvage, GO:0032263 GMP salvage and GO:0032265 XMP salvage. Supporting Evidence: PMID:5123876 An 8-azathioxanthine-resistant mutant lacked hypoxanthine phosphoribosyltransferase, xanthine phosphoribosyltransferase and guanine phosphoribosyltransferase activities (EC 2.4.2.8) and appeared to carry a single mutation. file:SCHPO/hpt1/hpt1-uniprot.txt Converts guanine to guanosine monophosphate, and hypoxanthine to inosine monophosphate. file:SCHPO/hpt1/hpt1-uniprot.txt Plays a central role in the generation of purine nucleotides through the purine salvage pathway (By similarity). |
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