Alt1 is a PLP-dependent alanine aminotransferase of Schizosaccharomyces pombe, assigned by conserved family features and orthology to characterized budding-yeast Alt1. It reversibly interconverts L-alanine plus 2-oxoglutarate with pyruvate plus L-glutamate, supporting inferred roles in alanine synthesis and utilization. Cytoplasmic and mitochondrial localization are curated assignments, with matrix activity inferred by PomBase; native localization and physiological flux have not been directly established in the evidence reviewed. The sequence differs from budding-yeast Alt1, but sequence length alone does not demonstrate loss of mitochondrial targeting.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004021 L-alanine:2-oxoglutarate transaminase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Rhea/EC 2.6.1.2 mapping from the UniProt by-similarity catalytic activity. alt1 is in PTHR11751:SF29 (alanine transaminase) and is the only ALT-family member in S. pombe; accepted, noting that activity has not been measured for the S. pombe protein (the S. cerevisiae paralog Alt2 shows that family members can be inert). Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt Reaction=L-alanine + 2-oxoglutarate = pyruvate + L-glutamate; PMID:19396236 under respiratory conditions, Alt1p constitutes the sole pathway for alanine biosynthesis and catabolism |
| GO:0004021 L-alanine:2-oxoglutarate transaminase activity | ISS GO_REF:0000024 | ACCEPT | Summary: Manual PomBase ISS from S. cerevisiae Alt1 (P52893), which is the active ALT; accepted on orthology, with the caveat that the inactive Alt2 paralog shows activity is not guaranteed by family membership. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt FUNCTION: Alanine aminotransferase involved in both alanine PMID:19396236 under respiratory conditions, Alt1p constitutes the sole pathway for alanine biosynthesis and catabolism PMID:23049841 only Alt1 displays alanine aminotransferase activity; in contrast ALT2 encodes a catalytically inert protein |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: Cytoplasmic localization is retained as a curated UniProt assignment; its precise subcompartment and relationship to the inferred mitochondrial pool remain unresolved. Reason: The curated localization statement supports this broad claim. Differences in sequence length and N-terminal composition do not establish loss of mitochondrial targeting or exclusive cytosolic residence. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000305}. Mitochondrion |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: Retain the supported mitochondrial localization alongside the existing matrix annotation. Reason: The UniProt subcellular-location mapping is consistent with the curated S. pombe mitochondrial location and experimentally localized S. cerevisiae Alt1. This remains a comparative localization inference: no native S. pombe matrix-resolved experiment is claimed, and the separately recorded cytoplasmic location is not excluded. Retain the informative mitochondrion assertion under the root-organelle policy; existing mitochondrial matrix annotations are separate and are not substituted for this row. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000305}. Mitochondrion file:yeast/ALT1/ALT1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix |
| GO:0005739 mitochondrion | ISS GO_REF:0000024 | ACCEPT | Summary: Retain the supported mitochondrial localization alongside the existing matrix annotation. Reason: The similarity-based mitochondrial assignment is consistent with the curated S. pombe mitochondrial location and experimentally localized S. cerevisiae Alt1. This remains a comparative localization inference: no native S. pombe matrix-resolved experiment is claimed, and the separately recorded cytoplasmic location is not excluded. Retain the informative mitochondrion assertion under the root-organelle policy; existing mitochondrial matrix annotations are separate and are not substituted for this row. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000305}. Mitochondrion file:yeast/ALT1/ALT1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix |
| GO:0005759 mitochondrial matrix | IC GO_REF:0000111 | ACCEPT | Summary: Mitochondrial localization is retained as a curated orthology-based inference, with matrix placement inferred by PomBase. Reason: The characterized S. cerevisiae Alt1 donor and target family assignment support the curated inference. A different sequence length or absence of an annotated transit peptide does not demonstrate targeting loss. No native S. pombe localization experiment is claimed. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt SUBCELLULAR LOCATION: Cytoplasm {ECO:0000305}. Mitochondrion file:yeast/ALT1/ALT1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix |
| GO:0008483 transaminase activity | IEA GO_REF:0000002 | MODIFY | Summary: The broad molecular-function annotation is true; the characterized or conserved L-alanine:2-oxoglutarate transaminase activity is the informative activity. Reason: Refine to L-alanine:2-oxoglutarate transaminase activity, already supported elsewhere in this review. This is term specificity, not a rejection of the original evidence. Proposed replacements: L-alanine:2-oxoglutarate transaminase activity Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt Reaction=L-alanine + 2-oxoglutarate = pyruvate + L-glutamate; |
| GO:0030170 pyridoxal phosphate binding | IEA GO_REF:0000002 | ACCEPT | Summary: Pyridoxal phosphate binding is integral to the aminotransferase catalytic mechanism. Reason: The cofactor-binding property is core to this enzyme, not peripheral merely because it is not an independent reaction. Direct target biochemical evidence, where available, and conserved PLP-dependent architecture support the claim. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt Name=pyridoxal 5'-phosphate; Xref=ChEBI:CHEBI:597326; |
| GO:0042852 L-alanine biosynthetic process | IC GO_REF:0000111 | ACCEPT | Summary: PomBase IC (with GO:0004021) from GO-CAM gomodel:67c10cc400000148 for L-alanine biosynthesis. Transamination of pyruvate with glutamate is the alanine-forming step and alt1 is the only ALT in S. pombe; in S. cerevisiae Alt1 is the sole alanine-forming route under respiratory growth. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt FUNCTION: Alanine aminotransferase involved in both alanine PMID:19396236 under respiratory conditions, Alt1p constitutes the sole pathway for alanine biosynthesis and catabolism |
| GO:0042853 L-alanine catabolic process | IC GO_REF:0000111 | ACCEPT | Summary: PomBase IC for L-alanine catabolic process (same GO-CAM); the reverse transamination converts alanine to pyruvate, as for S. cerevisiae Alt1. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt FUNCTION: Alanine aminotransferase involved in both alanine PMID:19396236 under respiratory conditions, Alt1p constitutes the sole pathway for alanine biosynthesis and catabolism |
| GO:0042853 L-alanine catabolic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway UPA00528 (L-alanine degradation via transaminase pathway) mapping; correct by orthology. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt PATHWAY: Amino-acid degradation; L-alanine degradation via transaminase |
| GO:0097054 L-glutamate biosynthetic process | IC GO_REF:0000111 | KEEP AS NON CORE | Summary: PomBase IC (with GO:0004021) for L-glutamate biosynthetic process from the glutamate GO-CAM. In the alanine-catabolic direction alt1 transfers the amino group to 2-oxoglutarate and so forms glutamate; the product is real but this is a by-product of alanine catabolism rather than a dedicated glutamate route. Reason: Glutamate is the co-product of alanine catabolism; secondary role. Supporting Evidence: file:SCHPO/alt1/alt1-uniprot.txt Reaction=L-alanine + 2-oxoglutarate = pyruvate + L-glutamate; |
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Download this section (compressed HTML)Q: Can native localization and import assays independently test the curated mitochondrial-matrix inference for S. pombe Alt1?
Q: How do carbon and nitrogen sources affect the direction and magnitude of Alt1-dependent alanine flux in fission yeast?
Experiment: Localise endogenously tagged alt1 with a mitochondrial marker, and measure ALT activity and alanine auxotrophy/utilisation in alt1-deleted cells.
Type: localisation, enzyme assay and growth phenotyping
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