Comparative transcriptome analysis reveals the mechanism underlying 3,5-dibromo-4-hydroxybenzoate catabolism via a new oxidative-decarboxylation pathway.

In this study, a new oxidative-decarboxylation pathway for DBHB catabolism was identified in a DBHB-utilizing strain of Pigmentiphaga sp. H8. The genetic determinants underlying this pathway were elucidated based on comparative transcriptome analysis and subsequent experimental validation. A gene cluster comprising orf420-orf426, with transcripts that were about 33∼4400-fold up-regulated in DBHB-induced cells compared with those in uninduced cells, was suspected to be involved in DBHB catabolism. The gene odcA (orf420), which is essential for the initial catabolism of DBHB, encodes a novel NAD(P)H-dependent flavin monooxygenase that mediates the oxidative decarboxylation of DBHB to 2,6-dibromohydroquinone (2,6-DBHQ). The substrate specificity of the purified OdcA indicated that the 4-hydroxyl group and its ortho-halogen(s) are important for hydroxylation of the 1-site carboxyl group by OdcA. Then, 2,6-DBHQ is ring-cleaved by the dioxygenase OdcB (Orf425) to 2-bromomaleylacetate, which is finally transformed to β-ketoadipate by the maleylacetate reductase OdcC (Orf426). These results provide a better understanding of the molecular mechanism underlying the catabolic diversity of halogenated para-hydroxybenzoates.IMPORTANCEHalogenated hydroxybenzoates (HBs), which are widely used synthetic precursors for chemical products and common metabolic intermediates from halogenated aromatics, exert considerable adverse effects on human health and ecological security. Microbial catabol...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research