title: Evolution of arginine biosynthesis in the bacterial domain: novel gene-enzyme relationships from psychrophilic Moritella strains (Vibrionaceae) and evolutionary significance of N-alpha-acetyl ornithinase.
abstract: In the arginine biosynthetic pathway of the vast majority of prokaryotes, the formation of ornithine is catalyzed by an enzyme transferring the acetyl group of N-alpha-acetylornithine to glutamate (ornithine acetyltransferase [OATase]) (argJ encoded). Only two exceptions had been reported-the Enterobacteriaceae and Myxococcus xanthus (members of the gamma and delta groups of the class Proteobacteria, respectively)-in which ornithine is produced from N-alpha-acetylornithine by a deacylase, acetylornithinase (AOase) (argE encoded). We have investigated the gene-enzyme relationship in the arginine regulons of two psychrophilic Moritella strains belonging to the Vibrionaceae, a family phylogenetically related to the Enterobacteriaceae. Most of the arg genes were found to be clustered in one continuous sequence divergently transcribed in two wings, argE and argCBFGH(A) ["H(A)" indicates that the argininosuccinase gene consists of a part homologous to known argH sequences and of a 3' extension able to complement an Escherichia coli mutant deficient in the argA gene, encoding N-alpha-acetylglutamate synthetase, the first enzyme committed to the pathway]. Phylogenetic evidence suggests that this new clustering pattern arose in an ancestor common to Vibrionaceae and Enterobacteriaceae, where OATase was lost and replaced by a deacylase. The AOase and ornithine carbamoyltransferase of these psychrophilic strains both display distinctly cold-adapted activity profiles, providing the first cold-active examples of such enzymes.
authors.affiliation: Laboratory for Genetics and Microbiology, Vrije Universiteit Brussel (VUB), and Department of Microbiology, Flanders Interuniversity Institute for Biotechnology, B-1070 Brussels, Belgium.
authors.forename: Y
authors.initials: Y
authors.lastname: Xu
authors.forename: Z
authors.initials: Z
authors.lastname: Liang
authors.forename: C
authors.initials: C
authors.lastname: Legrain
authors.forename: H J
authors.initials: HJ
authors.lastname: Rüger
authors.forename: N
authors.initials: N
authors.lastname: Glansdorff
mesh_terms: D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism; D000581:Amidohydrolases / Q000235:genetics* / Q000378:metabolism; D001120:Arginine / Q000096:biosynthesis*; D001483:Base Sequence; D003001:Cloning, Molecular; D003470:Culture Media; D004794:Enzyme Repression; D019143:Evolution, Molecular; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013696:Temperature; D014158:Transcription, Genetic; D014737:Vibrionaceae / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D014871:Water Microbiology
chemical_list: D003470:Culture Media; D012336:RNA, Ribosomal, 16S; D011994:Recombinant Proteins; D001120:Arginine; D000123:Acetyltransferases; C020646:glutamate acetyltransferase; D000581:Amidohydrolases; C018732:N-acetylornithine deacetylase