Biphenyl-associated meta-cleavage dioxygenases from Comamonas testosteroni B-356.

In addition to 2,3-dihydroxybiphenyl 1,2-dioxygenase (B1,2O), biphenyl-grown cells of Comamonas testosteroni B-356 were shown to produce a catechol 2,3-dioxygenase (C2,3O). B1,2O showed strong sequence homology with B1,2Os found in other biphenyl catabolic pathways, while partial sequence analysis of the C2,3O of B-356 suggested a relationship with xylEII-encoded C2,3O. The coexistence of two meta-cleavage dioxygenases in this strain prompted a comparison between the catalytic properties of the two enzymes. C2,3O has a much broader substrate specificity than native or His-tagged B1,2O: both enzymes were inhibited by chlorocatechols, but B1,2O was more sensitive than C2,3O. The results are discussed in terms of the physiological implications of interaction between metabolites from the lower biphenyl-chlorobiphenyl pathway and enzymes of the upper pathway.