MICROSOMAL ALCOHOL OXYGENASE - PURIFICATION AND CHARACTERIZATION OF ACYTOCHROME-P450 RESPONSIBLE FOR OXIDATION OF 7-HYDROXY-DELTA(8)-TETRAHYDROCANNABINOL TO 7-OXO-DELTA(8)-TETRAHYDROCANNABINOL IN GUINEA-PIG LIVER

Guinea pig hepatic enzyme, microsomal alcohol oxygenase, was able to o xidize both 7 alpha- and 7 beta-hydroxy-Delta(8)-tetrahydrocannabinol (7 alpha- and 7 beta-hydroxy-Delta(8)-THC) to 7-oxo-Delta(8)-THC. A cy tochrome P450, named P450GPF-B, which mediates this oxidative metaboli sm was purified from hepatic microsomes of untreated female guinea pig s. The purified enzyme showed a single protein band of molecular mass 50,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. T he NH2-terminal amino acid sequence of P450GPF-B is highly homologous with those of several cytochrome P450s belonging to the CYP3A subfamil y, O-18 derived from atmospheric oxygen was incorporated into 31 and 6 %, respectively, of 7-oxo-Delta(8)-THC formed from 7 alpha- and 7 beta -hydroxy-Delta(8)-THC when the substrates were incubated with P450GPF- B under O-18(2). The antibody against P450GPF-B significantly suppress ed the oxidative activities of 7 alpha- and 7 beta- hydroxy-Delta(8)-T HC to 7-oxo-Delta(8)-THC in hepatic microsomes of guinea pig, These re sults indicate that P450GPF-B is a major enzyme responsible for the he patic microsomal alcohol oxygenase activities in the guinea pig. (C) 1 997 Academic Press.