Acetylornithine aminotransferase (ACOAT; EC 2.6.1.11) of Saccharomyces cerevisiae, a pyridoxal 5'-phosphate-dependent class-III aminotransferase imported into the mitochondrial matrix via an N-terminal transit peptide. Arg8p transfers an amino group from L-glutamate to N-acetylglutamate 5-semialdehyde to form N2-acetyl-L-ornithine, the fourth reaction of the mitochondrial acetylated segment of arginine biosynthesis (ARG2/ARG5,6/ARG8/ARG7) that produces ornithine for export to the cytosolic citrulline/arginine steps. It is homologous to ornithine aminotransferases and can also transaminate ornithine in vitro, but this side activity is of little physiological importance.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Acetylornithine aminotransferase (EC 2.6.1.11) is the defining catalytic activity of Arg8p; the PANTHER node is a well-populated class-III aminotransferase ACOAT clade and S. cerevisiae ARG8 is itself one of the experimentally grounded members. Reason: Phylogenetic inference agrees with direct biochemical characterisation of yeast ACOAT. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt Reaction=N(2)-acetyl-L-ornithine + 2-oxoglutarate = N-acetyl-L-glutamate 5-semialdehyde + L-glutamate; PMID:2199330 Genes argD and ARG8, encoding the acetylornithine aminotransferase (ACOAT) subunit in Escherichia coli and Saccharomyces cerevisiae, respectively, have been cloned and sequenced. |
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | IDA PMID:2199330 Escherichia coli and Saccharomyces cerevisiae acetylornithin... | ACCEPT | Summary: Heimberg et al. cloned ARG8 and characterised the yeast ACOAT enzyme (UniProt cites this paper for EC 2.6.1.11 and a KM of 1.3 mM for acetylornithine). Core catalytic activity: fourth step of the acetylated arginine pathway (reverse of the reaction as written in Rhea), converting N-acetylglutamate 5-semialdehyde to N2-acetyl-L-ornithine. Reason: Direct experimental support for the core activity. Supporting Evidence: PMID:2199330 Genes argD and ARG8, encoding the acetylornithine aminotransferase (ACOAT) subunit in Escherichia coli and Saccharomyces cerevisiae, respectively, have been cloned and sequenced. file:yeast/ARG8/ARG8-uniprot.txt Reaction=N(2)-acetyl-L-ornithine + 2-oxoglutarate = N-acetyl-L-glutamate 5-semialdehyde + L-glutamate; |
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | IEA GO_REF:0000120 | ACCEPT | Summary: EC/Rhea-based mapping to the correct ACOAT term; consistent with experimental data. Reason: Correct mapping from EC 2.6.1.11. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt Reaction=N(2)-acetyl-L-ornithine + 2-oxoglutarate = N-acetyl-L-glutamate 5-semialdehyde + L-glutamate; |
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways assigns ARG8 to the acetylornithine aminotransferase step of arginine biosynthesis; this is correct. Reason: Pathway assignment agrees with experimental enzymology. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt catalyzes the conversion of N-acetylglutamate-gamma- |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | ACCEPT | Summary: ARG8 has supported mitochondrial localization; the matrix assertion is retained separately. Reason: The curated HDA row derives from the PROMITO mitochondrial proteome. It establishes an organelle-level location; the general dataset quotation is not by itself a target-specific matrix assay. The root-organelle policy preserves mitochondrion as an informative claim. Matrix localization was checked and remains a separate annotation, with its own experimental or inference basis. Supporting Evidence: PMID:205532 suggested that these enzymes were associated with the mitochondria. |
| GO:0005739 mitochondrion | HDA PMID:24769239 Quantitative variations of the mitochondrial proteome and ph... | ACCEPT | Summary: ARG8 has supported mitochondrial localization; the matrix assertion is retained separately. Reason: The curated HDA row derives from quantitative proteomics of isolated yeast mitochondria. Retain the organelle observation without treating the study-wide quotation as direct matrix resolution. The root-organelle policy preserves mitochondrion as an informative claim. Matrix localization was checked and remains a separate annotation, with its own experimental or inference basis. Supporting Evidence: PMID:205532 suggested that these enzymes were associated with the mitochondria. |
| GO:0005759 mitochondrial matrix | IBA GO_REF:0000033 | ACCEPT | Summary: Mitochondrial matrix localisation of fungal ACOAT is well supported; yeast Arg8p carries an N-terminal mitochondrial transit peptide (residues 1-13) and fractionates with mitochondria. Reason: Consistent with experimental localisation. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix {ECO:0000269|PubMed:205532}. |
| GO:0005759 mitochondrial matrix | IDA PMID:205532 Arginine metabolism in Saccharomyces cerevisiae: subcellular... | ACCEPT | Summary: Jauniaux et al. showed by fractionation of spheroplast lysates that the five enzymes of the acetylated compound cycle, including ACOAT, are particulate and co-fractionate with mitochondrial markers. Reason: Direct experimental support for mitochondrial (matrix) location. Supporting Evidence: PMID:205532 acetylornithine aminotransferase, and acetylornithine-glutamate acetyltransferase. These enzymes were exclusively particulate. PMID:205532 suggested that these enzymes were associated with the mitochondria. |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping to mitochondrial matrix; correct. Reason: Consistent with experimental localisation. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix {ECO:0000269|PubMed:205532}. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: The YeastPathways-to-GO-CAM conversion places Arg8p activity in the cytosol, but ACOAT is a mitochondrial matrix enzyme in S. cerevisiae (transit peptide, fractionation with mitochondria, mitochondrial proteomics). Only the steps from ornithine onward (CPSase, OTC, ASS, ASL) are cytosolic. Reason: PMID:205532 explicitly included acetylornithine aminotransferase among the measured activities restricted to particulate fractions, distinguished from the soluble downstream arginine-pathway enzymes. This is direct biochemical compartment discrimination for the target activity, not rejection from a targeting peptide or absence of a cytosolic database entry. It supports rejecting the pathway-derived cytosolic assignment under the measured native conditions; it does not prove that no precursor molecule or minor conditional pool can ever occur outside mitochondria. Unlike ARG7, no target-specific pre-import autocatalysis is established in the inspected evidence. Supporting Evidence: PMID:205532 acetylornithine aminotransferase, and acetylornithine-glutamate acetyltransferase. These enzymes were exclusively particulate. file:yeast/ARG8/ARG8-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion matrix {ECO:0000269|PubMed:205532}. |
| GO:0006525 arginine metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: Arg8p participates in arginine biosynthesis specifically; the InterPro-derived generic 'arginine metabolic process' is correct but less informative than L-arginine biosynthetic process, which the gene already carries. Reason: Replace with the specific biosynthetic process. Proposed replacements: L-arginine biosynthetic process Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt PATHWAY: Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl- |
| GO:0006526 L-arginine biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: ACOAT catalyses a step of de novo arginine biosynthesis (synthesis of N-acetylornithine, the precursor of ornithine). Reason: Core pathway. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt PATHWAY: Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl- |
| GO:0006526 L-arginine biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: UniPathway mapping (L-arginine biosynthesis, N2-acetyl-L-ornithine from L-glutamate, step 4/4); correct. Reason: Core pathway. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt PATHWAY: Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl- |
| GO:0006526 L-arginine biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways arginine biosynthesis assignment; correct. Reason: Core pathway. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt catalyzes the conversion of N-acetylglutamate-gamma- |
| GO:0006526 L-arginine biosynthetic process | TAS PMID:12603335 The N-acetylglutamate synthase/N-acetylglutamate kinase meta... | ACCEPT | Summary: Traceable author statement from a paper on the NAGS/NAGK metabolon of the same mitochondrial arginine pathway; the participation of ACOAT in arginine biosynthesis is not in doubt. Reason: Core pathway; consistent with UniProt and enzymology. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt PATHWAY: Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl- |
| GO:0006592 L-ornithine biosynthetic process | TAS PMID:205532 Arginine metabolism in Saccharomyces cerevisiae: subcellular... | ACCEPT | Summary: In yeast ornithine is made in mitochondria via the acetylated intermediates; ACOAT produces N-acetylornithine, from which ornithine is released by the ARG7 acetyltransferase. ACOAT therefore does part of the work of ornithine biosynthesis. Reason: Accurate, slightly more specific pathway segment than arginine biosynthesis. Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt PATHWAY: Amino-acid biosynthesis; L-arginine biosynthesis; N(2)-acetyl- PMID:205532 acetylornithine aminotransferase, and acetylornithine-glutamate acetyltransferase. These enzymes were exclusively particulate. |
| GO:0008483 transaminase activity | IEA GO_REF:0000002 | MODIFY | Summary: Generic transaminase activity from InterPro; the specific activity (N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase) is experimentally established. Reason: Replace with the specific child term. Proposed replacements: N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt Reaction=N(2)-acetyl-L-ornithine + 2-oxoglutarate = N-acetyl-L-glutamate 5-semialdehyde + L-glutamate; |
| GO:0030170 pyridoxal phosphate binding | IEA GO_REF:0000002 | ACCEPT | Summary: Arg8p is a class-III PLP-dependent aminotransferase; PLP is its cofactor. Reason: Correct cofactor-binding annotation (non-redundant with the catalytic term). Supporting Evidence: file:yeast/ARG8/ARG8-uniprot.txt Name=pyridoxal 5'-phosphate; Xref=ChEBI:CHEBI:597326; |
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