FIG. 1.

Reaction catalyzed by biphenyl-hydroxylating dioxygenases and the three subsequent steps of aerobic bacterial biphenyl catabolism. Enzymes: BphA1 and BphA2, alpha and beta subunits of biphenyl dioxygenase; BphA3, ferredoxin; BphA4, ferredoxin reductase; BphB, biphenyl-2,3-dihydrodiol 2,3-dehydrogenase; BphC, 2,3-dihydroxybiphenyl 1,2-dioxygenase; and BphD, 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase. Compounds: 1, biphenyl; 2, biphenyl-2,3-dihydrodiol; 3, 2,3-dihydroxybiphenyl; 4, 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid; 5a, 2-hydroxypenta-2,4-dienoic acid; and 5b, benzoic acid.