PURIFICATION AND CHARACTERIZATION OF CYTOCHROME-P450 3A ENZYME FROM HEPATIC MICROSOMES OF UNTREATED DOGUERA BABOONS

We isolated a form of cytochrome P450 (P450) from hepatic microsomes o f untreated doguera baboons. The final preparation (referred to as P45 0 BLa) was apparently homogenous, as judged by sodium dodecyl sulfate- polyacrylamide gel electrophoresis. The estimated minimum molecular we ight of P450 BLa was 50 kDa. The N-terminal amino acid sequence of P45 0 BLa (identified 10 residues) was identical with that of P450 3A8 pur ified from cynomolgus monkeys. This protein was cross-reactive with an tibodies raised against P450 3A4 and P450 CMLc which were P450 3A enzy mes purified from hepatic microsomes of humans and cynomolgus monkeys, respectively. P450 BLa was capable of catalyzing testosterone 6 beta- hydroxylation and zonisamide reduction. P450 BLa antibody inhibited th e activity of testosterone 6 beta-hydroxylase, but not the activities of testosterone 16 alpha- and 16 beta-hydroxylases in liver microsomes of doguera baboons. From these lines of evidence we conclude that P45 0 BLa can be classified as part of the P450 3A subfamily and acts as a constitutive testosterone 6 beta-hydroxylase in hepatic microsomes of doguera baboons.