Homologous Gene Clusters of Nicotine Catabolism, Including a New ω-amidase for α-ketoglutaramate, in Species of Three Genera of Gram-positive Bacteria

Res Microbiol. 2011 Apr;162(3):285-91. doi: 10.1016/j.resmic.2011.01.001. Epub 2011 Feb 1.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinomycetales / genetics*
  • Actinomycetales / metabolism
  • Amidohydrolases / genetics*
  • Amidohydrolases / metabolism
  • Arthrobacter / genetics*
  • Arthrobacter / metabolism
  • Catalytic Domain
  • Gene Order
  • Ketoglutaric Acids / metabolism*
  • Metabolic Networks and Pathways / genetics*
  • Models, Molecular
  • Multigene Family
  • Nicotine / metabolism*
  • Protein Structure, Tertiary
  • Rhodococcus / genetics*
  • Rhodococcus / metabolism

Substances

  • Ketoglutaric Acids
  • alpha-ketoglutaramate
  • Nicotine
  • Amidohydrolases
  • amidase