PT  - JOURNAL ARTICLE
AU  - Hiroi, Toyoko
AU  - Chow, Toshio
AU  - Imaoka, Susumu
AU  - Funae, Yoshihiko
TI  - Catalytic Specificity of CYP2D Isoforms in Rat and Human
AID  - 10.1124/dmd.30.9.970
DP  - 2002 Sep 01
TA  - Drug Metabolism and Disposition
PG  - 970--976
VI  - 30
IP  - 9
4099  - http://dmd.aspetjournals.org/content/30/9/970.short
4100  - http://dmd.aspetjournals.org/content/30/9/970.full
SO  - Drug Metab Dispos2002 Sep 01; 30
AB  - In rats, six cytochrome P450 (P450) 2D isoforms have been genetically identified. Nonetheless, there is little evidence of catalytic properties of each CYP2D isoform. In this study, using recombinant CYP2D isoforms (rat CYP2D1, CYP2D2, CYP2D3, and CYP2D4 and human CYP2D6) or hepatic microsomes, we investigated the catalytic specificity toward bufuralol, debrisoquine, and propranolol, which are frequently used as CYP2D substrates. Bufuralol was oxidized to three metabolites by rat and human hepatic microsomes. 1′-Hydroxybufuralol was the major metabolite. 1′2′-Ethenylbufuralol, one of the others, was identified as a novel metabolite. The formation of 1′-hydroxybufuralol and 1′2′-ethenylbufuralol in hepatic microsomes was inhibited by anti-CYP2D antibody, suggesting that these metabolites were formed by CYP2D isoforms. All rat and human recombinant CYP2D isoforms possessed activity for the 1′-hydroxylation of bufuralol, indicating that this catalytic property was common to all CYP2D isoforms. However, the 1′2′-ethenylation of bufuralol was catalyzed only by rat CYP2D4 and human CYP2D6. Debrisoquine was oxidized to two metabolites, 3-hydroxydebrisoquine, and 4-hydroxydebrisoquine, by hepatic microsomes. Recombinant CYP2D2 and CYP2D6 had very high levels of activity for the 4-hydroxylation of debrisoquine with lowKm values. Only CYP2D1 had a higher level of 3-hydroxylation than 4-hydroxylation activity. Propranolol 4-hydroxylation was catalyzed by CYP2D2, CYP2D4, and CYP2D6. The 7-hydroxylation of propranolol was catalyzed only by CYP2D2. In conclusion, in rats, bufuralol 1′2′-ethenylation activity was specific to CYP2D4 and debrisoquine 4-hydroxylation and propranolol 7-hydroxylation activities were specific to CYP2D2. These catalytic activities are useful as a probe for rat CYP2D isoforms. The American Society for Pharmacology and Experimental Therapeutics