The long range goal of this project is to study the oxidation of chemicals to toxic or carcinogenic metabolites by prostaglandin H synthase (PHS) and to demonstrate the importance of this enzyme system in chemical-induced toxicity or carcinogenesis. We have shown that aromatic amine carcinogens, are metabolized to mutagens by PHS. PHS dependent oxidation occurred by a free radical mechanism and resulted in the formation of DNA adducts which can be used as in vivo markers for PHS-dependent oxidation. We have further studied the formation of amine mutagens by PHS using bacterial tester systems having different levels of acetylase activity. Our data indicate that acetylase plays an important role in the formation of free radical mutagens from aromatic amines, including bladder carcinogen such as benzidine derivatives. We are currently investigating the differences between PHS and HRP as related to the formation of mutagens by these peroxidases and the formation of oxygenated metabolites of aromatic amines by PHS. We further studied peroxidase catalyzed GSH conjugate formation and showed that this reaction occurs with a number of chemicals that contain a conjugated double bond adjacent to a aromatic ring. The reaction appears to be a general mechanism for conjugate formation. We have also shown that P-450 metabolites of BP will enhance this reaction which serves as a mechanism for detoxication of carcinogens. We have investigated the dealkyaltion of a series of N-substituted aromatic amines by peroxidases. The mechanism by the removal and oxidation of the alkyl group depends on the chemical nature of the group. Our data suggest that PHS is a versatile enzyme system that can catalyze a variety of reactions which are important in the conversion of chemicals to carcinogenic metabolites in extra hepatic tissue.
