title: Characterization of the mbd cluster encoding the anaerobic 3-methylbenzoyl-CoA central pathway.
abstract: The mbd cluster encoding genes of the 3-methylbenzoyl-CoA pathway involved in the anaerobic catabolism of 3-methylbenzoate and m-xylene was characterized for the first time in the denitrifying β-Proteobacterium Azoarcus sp. CIB. The mbdA gene product was identified as a 3-methylbenzoate-CoA ligase required for 3-methylbenzoate activation; its substrate spectrum was unique in activating all three methylbenzoate isomers. An inducible 3-methylbenzoyl-CoA reductase (mbdONQP gene products), displaying significant amino acid sequence similarities to known class I benzoyl-CoA reductases catalysed the ATP-dependent reduction of 3-methylbenzoyl-CoA to a methyldienoyl-CoA. The mbdW gene encodes a methyldienoyl-CoA hydratase that hydrated the methyldienoyl-CoA to a methyl-6-hydroxymonoenoyl-CoA compound. The mbd cluster also contains the genes predicted to be involved in the subsequent steps of the 3-methylbenzoyl-CoA pathway as well as the electron donor system for the reductase activity. Whereas the catabolic mbd genes are organized in two divergent inducible operons, the putative mbdR regulatory gene was transcribed separately and showed constitutive expression. The efficient expression of the mbd genes required the oxygen-dependent AcpR activator, and it was subject of carbon catabolite repression by some organic acids and amino acids. Sequence analyses suggest that the mbd gene cluster was recruited by Azoarcus sp. CIB through horizontal gene transfer.
authors: Environmental Biology Department, Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040 Madrid, Spain.
authors: Javier F
authors: JF
authors: Juárez
authors: María T
authors: MT
authors: Zamarro
authors: Christian
authors: C
authors: Eberlein
authors: Matthias
authors: M
authors: Boll
authors: Manuel
authors: M
authors: Carmona
authors: Eduardo
authors: E
authors: Díaz
mesh_terms: D000214:Acyl Coenzyme A / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D000693:Anaerobiosis; D020627:Azoarcus / Q000145:classification / Q000201:enzymology* / Q000235:genetics*; D001565:Benzoates / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005810:Multigene Family / Q000235:genetics*; D009876:Operon; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D014992:Xylenes / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D001565:Benzoates; D014992:Xylenes; C044605:methyl benzoate; C037817:benzoyl-coenzyme A; D044925:Oxidoreductases Acting on CH-CH Group Donors; C109030:benzoyl-coenzyme A reductase (dearomatizing); C031285:3-xylene