title: Importance of CYP2D3 in polymorphism of diazepam p-hydroxylation in rats.
abstract: Diazepam was metabolized to three primary metabolites, 3-hydroxy-diazepam, N-desmethyl-diazepam, and p-hydroxy-diazepam. Our previous studies reported metabolic position-specific inter- or intrastrain differences in diazepam metabolism among Sprague-Dawley, Brown Norway, Dark Agouti, and Wistar rats. Especially, there were marked ( approximately 300 fold) inter- or intrastrain differences in diazepam p-hydroxylation activity at low concentration of substrate. In this study, we investigated the enzyme that catalyzes diazepam p-hydroxylation. The activity toward diazepam p-hydroxylation was inhibited by anti-cytochrome P450 2D (CYP2D) antibody, suggesting that this activity was catalyzed by CYP2D isoforms. Comparing the expression levels of the CYP2D subfamily in liver microsomes from various strains of rats using anti-CYP2D2 antibody, we found that there was a band of protein that was consistent with the phenotype of diazepam p-hydroxylation. N-terminal amino acid sequences of the specific protein exactly corresponded to those of CYP2D3, indicating that CYP2D3 might be involved in diazepam p-hydroxylation. Moreover, using rat CYP2D isoforms expressed in yeast, we tested CYP2Ds to catalyze diazepam p-hydroxylation. CYP2D1 and CYP2D2 practically did not participate in diazepam metabolism. On the other hand, diazepam p-hydroxylation was catalyzed by CYP2D3. CYP2D4 had high activity toward diazepam N-desmethylation, but not p-hydroxylation. In conclusion, the polymorphic expression of CYP2D3 caused the inter- or intrastrain differences in diazepam p-hydroxylation among rat strains or individuals.
authors.affiliation: Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine, Hokkaido University, N18W9 North Ward, Sapporo 060-0818, Japan.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Sakai
authors.forename: Konomu
authors.initials: K
authors.lastname: Saito
authors.forename: Hyung-Sub
authors.initials: HS
authors.lastname: Kim
authors.forename: Akio
authors.initials: A
authors.lastname: Kazusaka
authors.forename: Mayumi
authors.initials: M
authors.lastname: Ishizuka
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Funae
authors.forename: Shoichi
authors.initials: S
authors.lastname: Fujita
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000072467:Cytochrome P450 Family 2; D003975:Diazepam / Q000378:metabolism*; D006900:Hydroxylation; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000378:metabolism; D013045:Species Specificity
chemical_list: D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; C512157:Cyp2d3 protein, rat; D006899:Mixed Function Oxygenases; D000429:Alcohol Oxidoreductases; C504568:Cyp2d1 protein, rat; D000072467:Cytochrome P450 Family 2; D003975:Diazepam