Abstract
The common marmoset (Callithrix jacchus), a small New World monkey, due to their evolutionary closeness, has the potential for use in human drug development. Four novel cDNAs, encoding cytochrome P450 (P450) 2C18, 2C19, 2C58, and 2C76 were cloned from marmoset livers to characterize P450 2C molecular properties including P450 2C8 previously reported. The deduced amino acid sequence showed high sequence identities (>86%) to those of human P450 2Cs, except for marmoset P450 2C76 that has low sequence identity (~70%) to any human P450 2Cs. Phylogenetic analysis showed that marmoset P450 2Cs were more closely clustered with those of humans and macaques than other species investigated. Quantitative polymerase chain reaction analysis showed that all the marmoset P450 2C mRNAs were predominantly expressed in liver than among the other tissues tested. Marmoset P450 2C proteins were detected in liver by immunoblotting using antibodies against human P450 2Cs. Among marmoset P450 2Cs heterologously expressed in Escherichia coli, marmoset P450 2C19 efficiently catalyzed human P450 2C substrates, S-warfarin, diclofenac, tolbutamide, flurbiprofen, and omeprazole. Marmoset P450 2C19 had high Vmax and low Km values for S-warfarin 7-hydroxylation comparable to those in human liver microsomes, indicating similar warfarin stereoselectivity to findings in humans. Faster in vivo S-warfarin clearance than R- warfarin after intravenous administration of racemic warfarin (0.2 mg/kg) to marmosets was consistent with the in vitro kinetic parameters. These results indicated that marmoset P450 2C enzymes had functional characteristics similar to those of humans and also that P450 2C-dependent metabolic properties are likewise similar between marmosets and humans.
- The American Society for Pharmacology and Experimental Therapeutics