%0 Journal Article %A Takanori Hashizume %A Masashi Mise %A Satoshi Matsumoto %A Yoshiaki Terauchi %A Toshihiko Fujii %A Susumu Imaoka %A Yoshihiko Funae %A Tetsuya Kamataki %A Hisashi Miyazaki %T A Novel Cytochrome P450 Enzyme Responsible for the Metabolism of Ebastine in Monkey Small Intestine %D 2001 %J Drug Metabolism and Disposition %P 798-805 %V 29 %N 6 %X Small intestinal microsomes of cynomolgus monkeys were found to catalyze hydroxylation and dealkylation of an H1-antihistamine prodrug, ebastine. To identify the main enzyme responsible for ebastine hydroxylation, which has been hitherto unknown, we purified two cytochrome P450 isoforms, named P450 MI-2 and P450 MI-3, from the intestinal microsomes on the basis of the hydroxylation activity. P450 MI-2 and P450 MI-3 showed the respective apparent molecular weights of 56,000 and 53,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The internal amino acid sequence of P450 MI-2 had high similarity with those of human CYP4F2, CYP4F3, and CYP4F8. The first 27 amino acid residues of P450 MI-3 were highly homologous with those of monkey CYP3A8 and human CYP3A4/5/7. Furthermore, P450 MI-2 and P450 MI-3 were recognized by anti-CYP4F and anti-CYP3A antibodies, respectively, in immunoblot analysis and catalyzed leukotriene B4 ω-hydroxylation and testosterone 6β-hydroxylation, which are known to be mediated by CYP4F and CYP3A, respectively. Although both enzymes had ebastine hydroxylation activity, the V max value of P450 MI-2 was much higher than that of P450 MI-3 (37.0 versus 0.406 nmol/min/nmol of P450), and the former K M (5.1 μM) was smaller than the latter K M (10 μM). Anti-CYP4F antibody inhibited the hydroxylation in small intestinal microsomes strongly (70%), but anti-CYP3A antibody did not. These results indicate that P450 MI-2 belongs to the CYP4F subfamily and is mainly responsible for hydroxylation of ebastine in monkey small intestinal microsomes. This suggests that the small intestinal CYP4F enzyme, P450 MI-2, can play an important role in the metabolism of drugs given orally. The American Society for Pharmacology and Experimental Therapeutics %U https://dmd.aspetjournals.org/content/dmd/29/6/798.full.pdf