title: Homologous gene clusters of nicotine catabolism, including a new ω-amidase for α-ketoglutaramate, in species of three genera of Gram-positive bacteria.
abstract: Gram-positive soil bacteria Arthrobacter nicotinovorans, Nocardioides sp. JS614 and Rhodococcus opacus were shown to contain similarly organized clusters of homologous genes for nicotine catabolism. An uncharacterized gene of a predicted nitrilase within these gene clusters was cloned from A. nicotinovorans and biochemical data unexpectedly showed that the protein exhibited ω-amidase activity toward α-ketoglutaramate. Structural modelling of the protein suggested the presence of the catalytic triad Cys-Glu-Lys, characteristic of this class of enzymes, and supported α-ketoglutaramate as substrate. A-ketoglutaramate could be generated by hydrolytic cleavage of the C-N bond of the trihydroxypyridine ring produced by nicotine catabolism in these bacteria. This ω-amidase, together with glutamate dehydrogenase, may form a physiologically relevant enzyme couple, leading to transformation of metabolically inert α-ketoglutaramate derived from trihydroxypyridine into glutamate, a central compound of nitrogen metabolism.
authors.affiliation: Institute of Biochemistry and Molecular Biology, Centre for Biochemistry and Molecular Cell Research, Albert-Ludwigs University, Freiburg, Germany. cristina.cobzaru@biochemie.uni-freiburg.de
authors.forename: Cristina
authors.initials: C
authors.lastname: Cobzaru
authors.forename: Petra
authors.initials: P
authors.lastname: Ganas
authors.forename: Marius
authors.initials: M
authors.lastname: Mihasan
authors.forename: Paula
authors.initials: P
authors.lastname: Schleberger
authors.forename: Roderich
authors.initials: R
authors.lastname: Brandsch
mesh_terms: D000192:Actinomycetales / Q000235:genetics* / Q000378:metabolism; D000581:Amidohydrolases / Q000235:genetics* / Q000378:metabolism; D001173:Arthrobacter / Q000235:genetics* / Q000378:metabolism; D020134:Catalytic Domain; D023061:Gene Order; D007656:Ketoglutaric Acids / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008958:Models, Molecular; D005810:Multigene Family; D009538:Nicotine / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012240:Rhodococcus / Q000235:genetics* / Q000378:metabolism
chemical_list: D007656:Ketoglutaric Acids; C008230:alpha-ketoglutaramate; D009538:Nicotine; D000581:Amidohydrolases; C019665:amidase