Differences in the Catalytic Properties of CYP2B6s Between Common Marmoset and Human

Common marmoset (M) is easy in breeding and handling, having a possibility as a useful animal model in the safety evaluation of drug candidates. CYP2B6 is one of important CYP enzymes responsible for drug metabolism. In this study, we cloned a cDNA encoding a novel CYP2B6 from a total RNA of M liver, expressed its protein in insect cells and characterized its enzymatic property. The deduced amino acid sequence of M‐CYP2B6 showed 86.1% identity to that of H‐CYP2B6. Its enzymatic function was examined using two H‐CYP2B6 substrates, bupropion (BUP) and efavirenz (EFV). M‐CYP2B6 did not show any detectable activities for BUP or EFV under the conditions used, while H‐CYP2B6 clearly exhibited activities for the both substrates. Docking simulation indicated two amino acids (X and Z) located in the active‐site cavity of M‐CYP2B6 protein as key residues affecting the substrate specificity. We thus replaced these amino acids with those of H‐CYP2B6 by the site‐directed mutagenesis method. The substitution of X and Z of M‐CYP2B6 with human‐type amino acid residues markedly increased velocities comparing the wild type. Possible mechanisms will be discussed.