Differences in the functional interaction of two purified cytochrome P-450 isozymes with epoxide hydrolase.

The relative functional associations of two cytochrome P-450 isozymes with epoxide hydrolase were investigated in a reconstituted system containing highly purified enzymes. Cytochromes P-450 PB-B, the major hepatic form from phenobarbital-induced rats, and BNF-B, the major form from beta-naphthoflavone-induced rats, were compared, with naphthalene and 2,3- and 2,5-dichlorobiphenyl as substrates. The results indicate that cytochrome P-450 BNF-B is more firmly associated with epoxide hydrolase than is cytochrome P-450 PB-B, and the association has major consequences for chemical carcinogenicity and toxicology.