Degradation of polychlorinated biphenyl metabolites by naphthalene-catabolizing enzymes

The ability of the dehydrogenase and ring cleavage dioxygenase of the napht halene degradation pathway to transform 3,4-dihydroxylated biphenyl metabol ites was investigated. 1,2-Dihydro-1,2-dihydroxynaphthalene dehydrogenase w as expressed as a histidine-tagged protein. The purified enzyme transformed 2,3-dihydro-2,3-dihydroxybiphenyl, 3,4-dihydro-3,4-dihydroxybiphenyl, and 3,4-dihydro-3,1-dihydroxy-2,2',5,5' -tetrachlorobiphenyl to 2,3-dihydroxybi phenyl, 3,4-dihydroxybiphenyl (3,4-DHB), and 3,4-dihydroxy-2,2',5,5'-tetrac hlorobiphenyl (3,4-DH-2,2',5,5'-TCB), respectively, Our data also suggested that purified 1,2-dihydroxynaphthalene dioxygenase catalyzed the meta clea vage of 3,4-DHB in both the 2,3 and 4,5 positions. This enzyme cleaved 3,4- DH-2,2',5,5'-TCB and 3,4-DHB at similar rates. These results demonstrate th e utility of the naphthalene catabolic enzymes in expanding the ability of the bph pathway to degrade polychlorinated biphenyls.