DEGRADATION OF CHLOROBIPHENYLS CATALYZED BY THE BPH-ENCODED BIPHENYL-2,3-DIOXYGENASE AND BIPHENYL-2,3-DIHYDRODIOL-2,3-DEHYDROGENA OF PSEUDOMONAS SP LB400

In order to characterize the metabolites produced in vivo by biphenyl- 2,3-dioxygenase and biphenyl-2,3-dihydrodiol-2,3-dehydrogenase, the fi rst two enzymes of the (polychloro)biphenyl catabolic pathway encoded by the bph locus of Pseudomonas sp. LB400, recombinant E. coli strains expressing the respective genes were constructed. Biphenyl-2,3-dioxyg enase attack on 2,2'- or 2,4'-dichlorobiphenyl was shown to give rise to virtually quantitative ortho-dechlorination of these congeners by h ydroxylation at the chlorinated carbon 2 and its unsubstituted neighbo ur. Elimination of hydrochloric acid directly leads to 2,3-dihydroxy-c hlorobiphenyls and obviates the need for biphenyl-2,3-dihydrodiol-2,3- dehydrogenase for the catabolism of such congeners.