Purification and Characterization of Cytochrome P450 3A Enzyme from Hepatic Microsomes of Untreated Doguera Baboons

Abstract

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