Functional characterization of Corynebacterium glutamicum catechol 2, 3-dioxygenase induced by aromatic compounds.

In bacteria, phenolic compounds are usually metabolized via the catechol pathway, in which catechol undergoes ring-opening reactions catalyzed by catechol 1, 2-dioxygenase (C12O, ortho cleavage) or catechol 2, 3-dioxygenase (C23O, meta cleavage), eventually entering central carbon metabolism. Corynebacterium glutamicum can utilize phenol as the sole carbon and energy source. The function of its C12O (encoded by ncgl2319) has been confirmed, whereas the putative C23O (encoded by ncgl2007, designated cgc23o) remains uncharacterized. In this study, we functionally characterized CgC23O, a protein conserved among Corynebacteria. This enzyme exhibited C23O activity toward catechol (Km=5.38 ± 0.32 µM, kcat=2.61 ± 0.12 s-1, kcat/Km=4.85 ×105 M-1s-1), displayed preferential catalytic activity against 4-methylcatechol and 4-chlorocatechol, and acted as a Fe2+-dependent metalloprotein. Transcription of cgc23o was inducible by a broad spectrum of aromatic compounds. At low catechol or phenol concentrations, CgC23O and NCgl2319 were co-expressed and catalytically active; by contrast, at high substrate concentrations, CgC23O served as the dominant enzyme. These results clarify the significant role of CgC23O in the decomposition and assimilation of aromatic compounds in C. glutamicum.