Changes in the Enzymatic Properties of CYP2D6 by the Substitution of Phenylalanine at Position 120 by Alanine

• Published in: Journal of Health Science 2004, Vol.50(5), pp.503-510
• Main Authors: Masuda, Kazufumi, Hashimoto, Hiroki, Tamagake, Keietsu, Okuda, Yukie, Tsuzuki, Daisuke, Isobe, Takashi, Hichiya, Hiroyuki, Hanioka, Nobumitsu, Yamamoto, Shigeo, Narimatsu, Shizuo
• Format: Article
• Language: English
• Subjects: alanine-120; bunitrolol; cytochrome P450 2D6; debrisoquine; phenylalanine-120
• ISSN: 1344-9702; 1347-5207
• DOI: 10.1248/jhs.50.503

The functional roles of phenylalanine at position 120 (Phe-120) in the oxidation of bunitrolol (BTL), debrisoquine (DB) and bufuralol (BF) by cytochrome P450 2D6 (CYP2D6) were examined using a yeast cell expression system (Saccharomyces cerevisiae AH-22 strain). The substitution of Phe-120 by alanine markedly increased the activities of enantiomeric BTL 4-hydroxylase and DB 4-hydroxylase, whereas it did not remarkably affect BF 1′′-hydroxylase activities. Kinetic studies revealed that the substitution of Phe-120 by alanine increased the Km and Vmax values for enantiomeric BTL 4-hydroxylation, but increased only the Vmax value for DB 4-hydroxylation without changing the Km value. Km and Vmax values for BF 1′′-hydroxylation were similar between the mutant and the wild-type. The dissociation constants of the mutant calculated from the binding spectra for BTL enantiomers were higher than those of the wild-type, suggesting that the substitution of Phe-120 by alanine decreased the affinity of CYP2D6 for BTL enantiomers. These results indicate that Phe-120 has an important role in the oxidation of substrates by CYP2D6.