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Anaerobic degradation of 4-methylbenzoate via a specific 4-methylbenzoyl-CoA pathway

Authors

  • Sven Lahme,

    1. Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, D-26111 Oldenburg, Germany
    2. Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany
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  • Christian Eberlein,

    1. Institute of Biochemistry, University of Leipzig, Brüderstr. 24, D-04103 Leipzig, Germany
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  • René Jarling,

    1. Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam, Germany
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  • Michael Kube,

    1. Max Planck Institute for Molecular Genetics, Ihnestr. 73, D-14195 Berlin, Germany
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  • Matthias Boll,

    1. Institute of Biochemistry, University of Leipzig, Brüderstr. 24, D-04103 Leipzig, Germany
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  • Heinz Wilkes,

    1. Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Telegrafenberg, D-14473 Potsdam, Germany
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  • Richard Reinhardt,

    1. Max Planck Institute for Plant Breeding, Carl-von-Linné-Weg 10, D-50829 Köln, Germany
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  • Ralf Rabus

    Corresponding author
    1. Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, D-26111 Oldenburg, Germany
    2. Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359 Bremen, Germany
      E-mail: rabus@icbm.de; Tel. (+49) 441 798 3884; Fax (+49) 441 798 3404.
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E-mail: rabus@icbm.de; Tel. (+49) 441 798 3884; Fax (+49) 441 798 3404.

Summary

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.

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