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Review
Transcriptional regulation of catabolic pathways for aromatic compounds in Corynebacterium glutamicum
K. Brinkrolf1,2, I. Brune1 and A. Tauch1
1Institut für Genomforschung, Centrum für Biotechnologie,
Universität Bielefeld, Bielefeld, Germany
2International NRW Graduate School in Bioinformatics and Genome Research,
Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany
Corresponding author: A. Tauch
E-mail: Andreas.Tauch@Genetik.Uni-Bielefeld.DE
Genet. Mol. Res. 5 (4): 773-789 (2006)
Received July 24, 2006
Accepted November 6, 2006
Published December 7, 2006

ABSTRACT. Corynebacterium glutamicum is a gram-positive soil microorganism able to utilize a large variety of aromatic compounds as the sole carbon source. The corresponding catabolic routes are associated with multiple ring-fission dioxygenases and among other channeling reactions, include the gentisate pathway, the protocatechuate and catechol branches of the b-ketoadipate pathway and two potential hydroxyquinol pathways. Genes encoding the enzymatic machinery for the bioconversion of aromatic compounds are organized in several clusters in the C. glutamicum genome. Expression of the gene clusters is under specific transcriptional control, apparently including eight DNA-binding proteins belonging to the AraC, IclR, LuxR, PadR, and TetR families of transcriptional regulators. Expression of the gentisate pathway involved in the utilization of 3-hydroxybenzoate and gentisate is positively regulated by an IclR-type activator. The metabolic channeling of ferulate, vanillin and vanillate into the protocatechuate branch of the b-ketoadipate pathway is controlled by a PadR-like repressor. Regulatory proteins of the IclR and LuxR families participate in transcriptional regulation of the branches of the b-ketoadipate pathway that are involved in the utilization of benzoate, 4-hydroxybenzoate and protocatechuate. The channeling of phenol into this pathway may be under positive transcriptional control by an AraC-type activator. One of the potential hydroxyquinol pathways of C. glutamicum is apparently repressed by a TetR-type regulator. This global analysis revealed that transcriptional regulation of aromatic compound utilization is mainly controlled by single regulatory proteins sensing the presence of aromatic compounds, thus representing single input motifs within the transcriptional regulatory network of C. glutamicum.

Key words: Corynebacterium glutamicum, Corynebacterium efficiens, Gentisate pathway, b-ketoadipate pathway, Hydroxyquinol pathway, Transcriptional regulation

 

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