title: Selective deficiency of debrisoquine 4-hydroxylase activity in mouse liver microsomes.
abstract: Cytochrome P450 enzymes belonging to the CYP2D subfamily have been shown to be one of determinants of the polymorphic drug oxidations in the human and the rat. Debrisoquine 4-hydroxylation is a typical reaction catalyzed by these enzymes. However, various strains of mice were observed to have much lower debrisoquine 4-hydroxylase activity than Wistar rats, whereas other monooxygenase activities in mice toward bunitrolol, propranolol, imipramine and amitriptyline, which are mediated by the CYP2D enzymes in the rat, were comparable to those of the rats. Immunoblot analysis of mouse liver microsomes with an antibody raised against a rat CYP2D enzyme indicated that the mouse liver contained a P450 enzyme(s) immunochemically related to the rat CYP2D enzyme. The antibody inhibited propranolol ring-hydroxylase and imipramine 2-hydroxylase activities, as well as testosterone 16alpha-hydroxylase activity, a typical reaction of mouse CYP2D9, but not debrisoquine 4-hydroxylase activity in mouse liver microsomes. We partially purified a P450 enzyme (designated P450 ML2d) from livers of male ddY mice by monitoring the cross-reactivity with the antibody. The partially purified enzyme was indicated to belong to the CYP2D subfamily from its N-terminal amino acid sequence, but the homology of the sequence to other CYP2D enzymes of the mouse (CYP2D9-11) was 62%, suggesting that P450 ML2d is a novel P450 enzyme. P450 ML2d had the oxidation activities for the rat CYP2D-substrates, such as propranolol 4-hydroxylation and imipramine 2-hydroxylation, in higher rates than those of the microsomes, but did not exhibit debrisoquine 4-hydroxylase activity. Our result is the first finding that a mouse CYP2D enzyme also metabolizes substrates for the rat CYP2D enzyme, in addition to steroids, but the enzyme had a limited specificity for the substrates of the CYP2D enzymes of the rat and the human.
authors.affiliation: Laboratory of Biopharmaceutics, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Masubuchi
authors.forename: T
authors.initials: T
authors.lastname: Iwasa
authors.forename: S
authors.initials: S
authors.lastname: Hosokawa
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: T
authors.initials: T
authors.lastname: Horie
authors.forename: S
authors.initials: S
authors.lastname: Imaoka
authors.forename: Y
authors.initials: Y
authors.lastname: Funae
authors.forename: S
authors.initials: S
authors.lastname: Narimatsu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D065727:Cytochrome P-450 CYP2C8; D065729:Cytochrome P-450 CYP2C9; D019389:Cytochrome P-450 CYP2D6 / Q000172:deficiency*; D000072467:Cytochrome P450 Family 2; D005260:Female; D006168:Guinea Pigs; D015151:Immunoblotting; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D008862:Microsomes, Liver / Q000201:enzymology*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D039181:Steroid 16-alpha-Hydroxylase; D013739:Testosterone / Q000378:metabolism
chemical_list: D013739:Testosterone; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; C450259:CYP2C8 protein, human; D065727:Cytochrome P-450 CYP2C8; D019389:Cytochrome P-450 CYP2D6; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase