astC (b1748; also cstC, argM) encodes succinylornithine transaminase (SOAT, EC 2.6.1.81) of Escherichia coli, a dimeric, cytoplasmic pyridoxal 5'-phosphate-dependent class-III aminotransferase. It transaminates N2-succinyl-L-ornithine with 2-oxoglutarate to N-succinyl-L-glutamate 5-semialdehyde and L-glutamate, the third reaction of the ammonia-producing arginine succinyltransferase (AST) pathway, and is the first gene of the nitrogen- and sigma S-regulated astCADBE operon. Loss of AstC abolishes growth on arginine as nitrogen source and impairs ornithine utilization. AstC also has N-acetylornithine transaminase activity and is one of several redundant enzymes that can supply that step of arginine biosynthesis, although ArgD is the main biosynthetic enzyme.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PAINT IBA from PTN000241318, the ArgD/AstC clade of PTHR11986; this gene is among the seeds. Reason: AstC has genuine N-acetylornithine transaminase activity and can supply it in arginine synthesis, but ArgD is the major biosynthetic enzyme and AstC is the catabolic, nitrogen-regulated AST enzyme. A real secondary activity of a dedicated catabolic enzyme is non-core. The node placement is sound; the issue is only core versus secondary. Supporting Evidence: PMID:25243376 The enzymes with N-acetylornithine aminotransferase (ACOAT) activity in arginine synthesis were ArgD, AstC, GabT and PuuE; the major anaerobic ACOAT was ArgD. file:ECOLI/astC/astC-uniprot.txt Catalyzes the transamination of N(2)-succinylornithine and alpha-ketoglutarate into N(2)-succinylglutamate semialdehyde and glutamate. Can also act as an acetylornithine aminotransferase. |
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | IDA PMID:25243376 The redundant aminotransferases in lysine and arginine synth... | KEEP AS NON CORE | Summary: Complementation and activity data identify AstC as one of four E. coli enzymes with ACOAT activity in arginine synthesis. Reason: AstC has genuine N-acetylornithine transaminase activity and can supply it in arginine synthesis, but ArgD is the major biosynthetic enzyme and AstC is the catabolic, nitrogen-regulated AST enzyme. A real secondary activity of a dedicated catabolic enzyme is non-core. Supporting Evidence: PMID:25243376 The enzymes with N-acetylornithine aminotransferase (ACOAT) activity in arginine synthesis were ArgD, AstC, GabT and PuuE; the major anaerobic ACOAT was ArgD. |
| GO:0003992 N2-acetyl-L-ornithine:2-oxoglutarate 5-transaminase activity | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA-based ACOAT activity. Reason: AstC has genuine N-acetylornithine transaminase activity and can supply it in arginine synthesis, but ArgD is the major biosynthetic enzyme and AstC is the catabolic, nitrogen-regulated AST enzyme. A real secondary activity of a dedicated catabolic enzyme is non-core. Same claim as the IBA and IDA rows. Supporting Evidence: PMID:25243376 The enzymes with N-acetylornithine aminotransferase (ACOAT) activity in arginine synthesis were ArgD, AstC, GabT and PuuE; the major anaerobic ACOAT was ArgD. |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA cytosol from PTN000241318, seeded by E. coli PatA. Reason: AstC is a soluble class-III PLP aminotransferase without signal peptide or transmembrane segment acting on cytoplasmic pathway intermediates; consistent with the ArgD/AstC clade and with the aruC ortholog review. Supporting Evidence: file:ECOLI/astC/astC-uniprot.txt SIMILARITY: Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. AstC subfamily. PMID:23484010 AstC is a dimeric, pyridoxal phosphate (PLP)-dependent ฮดโaminotransferase that operates a ping-pong bi-bi reaction mechanism with succinylornithine (SO) and ฮฑ-ketoglutarate (ฮฑKG) as co-substrates and succinylglutamic semialdehyde and glutamate as co-products |
| GO:0006520 amino acid metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO from IPR017652 (Ac/SucOrn transaminase). Reason: Correct but general; the specific processes are already carried by the gene: L-arginine catabolism (core) and L-arginine biosynthesis (secondary). Proposed replacements: L-arginine catabolic process L-arginine biosynthetic process Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. PMID:25243376 The enzymes with N-acetylornithine aminotransferase (ACOAT) activity in arginine synthesis were ArgD, AstC, GabT and PuuE; the major anaerobic ACOAT was ArgD. |
| GO:0006525 arginine metabolic process | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO from IPR004636 (AcOrn/SuccOrn aminotransferase). Reason: Correct but general; both specific arginine processes are supported and already carried by the gene. Proposed replacements: L-arginine catabolic process L-arginine biosynthetic process Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. PMID:25243376 The enzymes with N-acetylornithine aminotransferase (ACOAT) activity in arginine synthesis were ArgD, AstC, GabT and PuuE; the major anaerobic ACOAT was ArgD. |
| GO:0006526 L-arginine biosynthetic process | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: PAINT IBA arginine biosynthesis from PTN000241318 (seed P. aeruginosa AruC). Reason: AstC can provide the ACOAT step of arginine synthesis (it complements, and is one of four redundant ACOATs), so the inherited process is true for this gene, but it is secondary to the catabolic role. Supporting Evidence: PMID:25243376 The enzymes with N-acetylornithine aminotransferase (ACOAT) activity in arginine synthesis were ArgD, AstC, GabT and PuuE; the major anaerobic ACOAT was ArgD. |
| GO:0006527 L-arginine catabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA from PTN001736444 seeded by this gene. Reason: AstC catalyzes step 3 of the AST pathway, which E. coli needs to catabolize arginine. Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. PMID:9696779 We identified the E. coli gene for succinylornithine aminotransferase, the third enzyme of the AST pathway, which appears to be the first of an astCADBE operon. |
| GO:0006527 L-arginine catabolic process | IEA GO_REF:0000120 | ACCEPT | Summary: HAMAP/InterPro (SOAT, IPR026330) mapping. Reason: AstC catalyzes step 3 of the AST pathway, which E. coli needs to catabolize arginine. Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. |
| GO:0006527 L-arginine catabolic process | IMP PMID:9696779 Arginine catabolism and the arginine succinyltransferase pat... | ACCEPT | Summary: astC disruption prevents arginine catabolism. Reason: AstC catalyzes step 3 of the AST pathway, which E. coli needs to catabolize arginine. Direct genetic evidence. Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. |
| GO:0006593 L-ornithine catabolic process | IEA GO_REF:0000002 | KEEP AS NON CORE | Summary: InterPro2GO from IPR026330 (SOAT). Reason: Real but peripheral. astC disruption impairs ornithine utilization; the AST route handles ornithine through succinylornithine, the AstC substrate, but this is a secondary use of the arginine pathway enzyme. As precise as the evidence allows. Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. |
| GO:0006593 L-ornithine catabolic process | IMP PMID:9696779 Arginine catabolism and the arginine succinyltransferase pat... | KEEP AS NON CORE | Summary: astC disruption impairs ornithine utilization. Reason: Real but peripheral. astC disruption impairs ornithine utilization; the AST route handles ornithine through succinylornithine, the AstC substrate, but this is a secondary use of the arginine pathway enzyme. As precise as the evidence allows. Supporting Evidence: PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. |
| GO:0006593 L-ornithine catabolic process | IMP PMID:9696780 The Escherichia coli starvation gene cstC is involved in ami... | KEEP AS NON CORE | Summary: cstC (astC) mutants are impaired in using amino acids as nitrogen sources. Reason: Real but peripheral. astC disruption impairs ornithine utilization; the AST route handles ornithine through succinylornithine, the AstC substrate, but this is a secondary use of the arginine pathway enzyme. As precise as the evidence allows. This paper shows a general amino-acid nitrogen-utilization defect and does not resolve ornithine specifically; the row is consistent with PMID:9696779. Supporting Evidence: PMID:9696780 Escherichia coli strains mutant in the starvation gene cstC grow normally in a mineral salts medium but are impaired in utilizing amino acids as nitrogen sources. PMID:9696779 Its disruption prevented arginine catabolism, impaired ornithine utilization, and affected the synthesis of all the enzymes of the AST pathway. |
| GO:0008483 transaminase activity | IEA GO_REF:0000120 | MODIFY | Summary: Generic transaminase activity from InterPro/HAMAP. Reason: Correct but general; the specific succinylornithine transaminase activity is established and already carried by the gene. Proposed replacements: succinylornithine:2-oxoglutarate transaminase activity Supporting Evidence: PMID:23484010 AstC is a dimeric, pyridoxal phosphate (PLP)-dependent ฮดโaminotransferase that operates a ping-pong bi-bi reaction mechanism with succinylornithine (SO) and ฮฑ-ketoglutarate (ฮฑKG) as co-substrates and succinylglutamic semialdehyde and glutamate as co-products |
| GO:0030170 pyridoxal phosphate binding | IEA GO_REF:0000120 | KEEP AS NON CORE | Summary: PLP binding from InterPro/HAMAP. Reason: AstC is a PLP-dependent aminotransferase, so cofactor binding is true and as precise as warranted, but it is supporting chemistry for the transaminase activity. Supporting Evidence: PMID:23484010 AstC is a dimeric, pyridoxal phosphate (PLP)-dependent ฮดโaminotransferase that operates a ping-pong bi-bi reaction mechanism with succinylornithine (SO) and ฮฑ-ketoglutarate (ฮฑKG) as co-substrates and succinylglutamic semialdehyde and glutamate as co-products |
| GO:0043825 succinylornithine:2-oxoglutarate transaminase activity | IDA PMID:9696779 Arginine catabolism and the arginine succinyltransferase pat... | ACCEPT | Summary: Identification of astC as the succinylornithine aminotransferase gene of the AST pathway. Reason: Core activity of AstC, the defining step-3 reaction of the pathway; corroborated by structural and docking work with succinylornithine. Supporting Evidence: PMID:9696779 We identified the E. coli gene for succinylornithine aminotransferase, the third enzyme of the AST pathway, which appears to be the first of an astCADBE operon. PMID:23484010 AstC is a dimeric, pyridoxal phosphate (PLP)-dependent ฮดโaminotransferase that operates a ping-pong bi-bi reaction mechanism with succinylornithine (SO) and ฮฑ-ketoglutarate (ฮฑKG) as co-substrates and succinylglutamic semialdehyde and glutamate as co-products |
| GO:0043825 succinylornithine:2-oxoglutarate transaminase activity | IEA GO_REF:0000120 | ACCEPT | Summary: InterPro/EC/Rhea mapping of the SOAT reaction. Reason: Same correct core claim as the IDA row. Supporting Evidence: file:ECOLI/astC/astC-uniprot.txt Catalyzes the transamination of N(2)-succinylornithine and alpha-ketoglutarate into N(2)-succinylglutamate semialdehyde and glutamate. Can also act as an acetylornithine aminotransferase. |
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Download this section (compressed HTML)Q: Complementation identifies AstC as one of the major N-succinyl-L,L-diaminopimelate aminotransferases (SDAP-ATs) of lysine synthesis, alongside ArgD and SerC. How much SDAP-AT flux does AstC carry in wild-type cells, given that the ast operon is induced mainly by nitrogen limitation?
Suggested experts: bacterial amino acid metabolism
Experiment: Steady-state kinetics of purified AstC with succinylornithine, acetylornithine and N-succinyl-2-amino-6-oxopimelate, compared with ArgD.
Type: enzyme kinetics
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