title: Anaerobic degradation of 4-methylbenzoate via a specific 4-methylbenzoyl-CoA pathway.
abstract: The pathway for anaerobic degradation of 4-methylbenzoate was studied in the denitrifying alphaproteobacterium Magnetospirillum sp. strain pMbN1. Adaptation studies with whole cells indicated substrate-dependent induction of the capacity to degrade 4-methylbenzoate. Differential protein profiling (2D-DIGE) of 4-methylbenzoate- in comparison with benzoate- or succinate-adapted cells revealed the specific abundance increase of substrate-specific protein sets. Their coding genes form distinct clusters on the genome, two of which were assigned to 4-methylbenzoate and one to benzoate degradation. The predicted functions of the gene products agree with a specific 4-methylbenzoyl-CoA degradation pathway in addition to and analogous to the known anaerobic benzoyl-CoA degradation pathway. In vitro benzoyl-CoA and 4-methylbenzoyl-CoA reductase activities revealed the electron donor and ATP-dependent formation of the corresponding conjugated cyclic dienoyl-CoA/4-methyl-dienoyl-CoA products. The 4-methylbenzoyl-CoA reductase activity was induced in the presence of 4-methylbenzoate. In accordance, metabolite analysis of cultures grown with 4-methylbenzoate tentatively identified 4-methylcyclohex-1,5-diene-1-carboxylate. The 4-methylbenzoate induced genes were assigned to code for the putative 4-methylbenzoyl-CoA reductase; their products display pronounced sequence disparity from the conventional class I benzoyl-CoA reductase, which does not accept substituents at the para-position. Identification of 3-methylglutarate together with the formation of specific proteins for ring cleavage and β-oxidation in 4-methylbenzoate-adapted cells suggest conservation of the methyl group along the specific 4-methylbenzoyl-CoA degradation pathway.
authors.affiliation: Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Carl-von-Ossietzky-Strasse 9-11, Oldenburg, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Lahme
authors.forename: Christian
authors.initials: C
authors.lastname: Eberlein
authors.forename: René
authors.initials: R
authors.lastname: Jarling
authors.forename: Michael
authors.initials: M
authors.lastname: Kube
authors.forename: Matthias
authors.initials: M
authors.lastname: Boll
authors.forename: Heinz
authors.initials: H
authors.lastname: Wilkes
authors.forename: Richard
authors.initials: R
authors.lastname: Reinhardt
authors.forename: Ralf
authors.initials: R
authors.lastname: Rabus
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D000693:Anaerobiosis; D001565:Benzoates / Q000378:metabolism*; D020869:Gene Expression Profiling; D016680:Genome, Bacterial; D042201:Magnetospirillum / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010084:Oxidation-Reduction; D010802:Phylogeny; D020543:Proteome
chemical_list: D000214:Acyl Coenzyme A; D001565:Benzoates; D020543:Proteome; C037817:benzoyl-coenzyme A; C009504:4-toluic acid