Publications

• The dual biosynthetic capability of N-acetylornithine aminotransferase in arginine and lysine biosynthesis.

  Ledwidge R., Blanchard J.S.

  The genes encoding the seven enzymes needed to synthesize L-lysine from aspartate semialdehyde and pyruvate have been identified in a number of bacterial genera, with the single exception of the dapC gene encoding the PLP-dependent N-succinyl-L, L-diaminopimelate:alpha-ketoglutarate aminotransfera ... >> More

  The genes encoding the seven enzymes needed to synthesize L-lysine from aspartate semialdehyde and pyruvate have been identified in a number of bacterial genera, with the single exception of the dapC gene encoding the PLP-dependent N-succinyl-L, L-diaminopimelate:alpha-ketoglutarate aminotransferase (DapATase). Purification of E. coli DapATase allowed the determination of both the amino-terminal 26 amino acids and a tryptic peptide fragment. Sequence analysis identified both of these sequences as being identical to corresponding sequences from the PLP-dependent E. coli argD-encoded N-acetylornithine aminotransferase (NAcOATase). This enzyme performs a similar reaction to that of DapATase, catalyzing the N-acetylornithine-dependent transamination of alpha-ketoglutarate. PCR cloning of the argD gene from genomic E. coli DNA, expression, and purification yielded homogeneous E. coli NAcOATase. This enzyme exhibits both NAcOATase and DapATase activity, with similar specificity constants for N-acetylornithine and N-succinyl-L,L-DAP, suggesting that it can function in both lysine and arginine biosynthesis. This finding may explain why numerous investigations have failed to identify genetically the bacterial dapC locus, and suggests that this enzyme may be an attractive target for antibacterial inhibitor design due to the essential roles of these two pathways in bacteria. << Less

  Biochemistry 38:3019-3024(1999) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Structure of biosynthetic N-acetylornithine aminotransferase from Salmonella typhimurium: studies on substrate specificity and inhibitor binding.

  Rajaram V., Ratna Prasuna P., Savithri H.S., Murthy M.R.

  Acetylornithine aminotransferase (AcOAT) is one of the key enzymes involved in arginine metabolism and catalyzes the conversion of N-acetylglutamate semialdehyde to N-acetylornithine (AcOrn) in the presence of L-glutamate. It belongs to the Type I subgroup II family of pyridoxal 5'-phosphate (PLP) ... >> More

  Acetylornithine aminotransferase (AcOAT) is one of the key enzymes involved in arginine metabolism and catalyzes the conversion of N-acetylglutamate semialdehyde to N-acetylornithine (AcOrn) in the presence of L-glutamate. It belongs to the Type I subgroup II family of pyridoxal 5'-phosphate (PLP) dependent enzymes. E. coli biosynthetic AcOAT (eAcOAT) also catalyzes the conversion of N-succinyl-L-2-amino-6-oxopimelate to N-succinyl-L,L-diaminopimelate, one of the steps in lysine biosynthesis. In view of the critical role of AcOAT in lysine and arginine biosynthesis, structural studies were initiated on the enzyme from S. typhimurium (sAcOAT). The K(m) and k(cat)/K(m) values determined with the purified sAcOAT suggested that the enzyme had much higher affinity for AcOrn than for ornithine (Orn) and was more efficient than eAcOAT. sAcOAT was inhibited by gabaculine (Gcn) with an inhibition constant (K(i)) of 7 microM and a second-order rate constant (k(2)) of 0.16 mM(-1) s(-1). sAcOAT, crystallized in the unliganded form and in the presence of Gcn or L-glutamate, diffracted to a maximum resolution of 1.90 A and contained a dimer in the asymmetric unit. The structure of unliganded sAcOAT showed significant electron density for PLP in only one of the subunits (subunit A). The asymmetry in PLP binding could be attributed to the ordering of the loop L(alphak-) (betam) in only one subunit (subunit B; the loop from subunit B comes close to the phosphate group of PLP in subunit A). Structural and spectral studies of sAcOAT with Gcn suggested that the enzyme might have a low affinity for PLP-Gcn complex. Comparison of sAcOAT with T. thermophilus AcOAT and human ornithine aminotransferase suggested that the higher specificity of sAcOAT towards AcOrn may not be due to specific changes in the active site residues but could result from minor conformational changes in some of them. This is the first structural report of AcOAT from a mesophilic organism and could serve as a basis for drug design as the enzyme is important for bacterial cell wall biosynthesis. << Less

  Proteins 70:429-441(2008) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Cloning and characterization of the aru genes encoding enzymes of the catabolic arginine succinyltransferase pathway in Pseudomonas aeruginosa.

  Itoh Y.

  The arginine succinyltransferase (AST) pathway is the major arginine and ornithine utilization (aru) pathway under aerobic conditions in Pseudomonas aeruginosa. A 26-kb DNA fragment of the P. aeruginosa PAO1 chromosome carrying the regulatory argR gene and the aru structural gene cluster was clone ... >> More

  The arginine succinyltransferase (AST) pathway is the major arginine and ornithine utilization (aru) pathway under aerobic conditions in Pseudomonas aeruginosa. A 26-kb DNA fragment of the P. aeruginosa PAO1 chromosome carrying the regulatory argR gene and the aru structural gene cluster was cloned. Complementation tests and nucleotide sequence data established the locations of the argR, aruC, aruF, aruG, aruD, aruB, and aruE genes, in that order. The aruR, aruC, aruD, aruB, and aruE genes specify the ArgR regulatory protein, N2-succinylornithine 5-aminotransferase, N-succinylglutamate 5-semialdehyde dehydrogenase, N2-succinylarginine dihydrolase, and N-succinylglutamate desuccinylase, respectively, and the aruF and aruG genes encode the subunits (AruAI and AruAII) of arginine and ornithine N2-succinyltransferases. Furthermore, in vivo analysis of transcriptional aru fusions and of polar insertion mutations located at different sites in the aru cluster indicated the presence of three transcriptional units which are controlled by ArgR. The aruCFGDB genes appear to form an operon transcribed from a promoter upstream of aruC, whereas aruE has its own promoter. The argR gene, which is located upstream of the aruCFGDB operon, is a member of another (aot) operon coding for arginine transport genes. The deduced amino acid sequences of the AST enzymes were compared to those of homologous proteins of Escherichia coli specified by the ast genes lying in the chromosome region from 39.2 to 39.5 min (Kohara clone 327; GenBank/EMBL/DDJB accession no. D90818). The overall organization of the aru and ast genes in both organisms is similar, with the exception that E. coli appears to have a single AST gene. << Less

  J. Bacteriol. 179:7280-7290(1997) [PubMed] [EuropePMC]

  This publication is cited by 5 other entries.