Degradation of 2,3-Dihydroxybenzoate by a Novel meta-Cleavage Pathway

• Published in: Journal of Bacteriology 2012-08, Vol.194 (15), p.3851-3860
• Main Authors: Marín, Macarena, Plumeier, Iris, Pieper, Dietmar H
• Format: Article
• Language: English
• Subjects: Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Biosynthesis; Biotransformation; catechol; dehydrogenation; DNA, Bacterial - chemistry; DNA, Bacterial - genetics; Enzymes; Fundamental and applied biological sciences. Psychology; Gene Deletion; Gene expression; Gene Expression Profiling; Gene Order; genes; Hydroxybenzoates - metabolism; Kinetics; Metabolic Networks and Pathways - genetics; Metabolism; Microbiology; Miscellaneous; Molecular Sequence Data; Multigene Family; Phylogeny; Pseudomonas; Pseudomonas - genetics; Pseudomonas - growth & development; Pseudomonas - metabolism; secondary metabolites; Sequence Analysis, DNA; Sequence Homology, Amino Acid; siderophores; Substrate Specificity; transcription (genetics)
• ISSN: 0021-9193; 1098-5530; 1067-8832
• DOI: 10.1128/JB.00430-12

2,3-Dihydroxybenzoate is the precursor in the biosynthesis of several siderophores and an important plant secondary metabolite that, in bacteria, can be degraded via meta-cleavage of the aromatic ring. The dhb cluster of Pseudomonas reinekei MT1 encodes a chimeric meta-cleavage pathway involved in the catabolism of 2,3-dihydroxybenzoate. While the first two enzymes, DhbA and DhbB, are phylogenetically related to those involved in 2,3-dihydroxy-p-cumate degradation, the subsequent steps are catalyzed by enzymes related to those involved in catechol degradation (DhbCDEFGH). Characterization of kinetic properties of DhbA extradiol dioxygenase identified 2,3-dihydroxybenzoate as the preferred substrate. Deletion of the encoding gene impedes growth of P. reinekei MT1 on 2,3-dihydroxybenzoate. DhbA catalyzes 3,4-dioxygenation with 2-hydroxy-3-carboxymuconate as the product, which is then decarboxylated by DhbB to 2-hydroxymuconic semialdehyde. This compound is then subject to dehydrogenation and further degraded to citrate cycle intermediates. Transcriptional analysis revealed genes of the dhB gene cluster to be highly expressed during growth with 2,3-dihydroxybenzoate, whereas a downstream-localized gene encoding 2-hydroxymuconic semialdehyde hydrolase, dispensable for 2,3-dihydroxybenzoate metabolism but crucial for 2,3-dihydroxy-p-cumate degradation, was only marginally expressed. This is the first report describing a gene cluster encoding enzymes for the degradation of 2,3-dihydroxybenzoate.