Characterization of rat and human CYP2J enzymes as Vitamin D 25-hydroxylases.
vitamin D is 25-hydroxylated in the liver, before being activated by 1alpha-hydroxylation in the kidney. Recently, the rat cytochrome P450 2J3 (CYP2J3) has been identified as a principal vitamin D 25-hydroxylase in the rat [Yamasaki T, Izumi S, Ide H, Ohyama Y. Identification of a novel rat microsomal vitamin D(3) 25-hydroxylase. J Biol Chem 2004;279(22):22848-56]. In this study, we examine whether human CYP2J2 that exhibits 73% amino acid homology to rat CYP2J3 has similar catalytic properties. Recombinant human CYP2J2 was overexpressed in Escherichia coli, purified, and assayed for vitamin D 25-hydroxylation activity. We found significant 25-hydroxylation activity toward vitamin D(3) (turnover number, 0.087min(-1)), vitamin D(2) (0.16min(-1)), and 1alpha-hydroxyvitamin D(3) (2.2min(-1)). Interestingly, human CYP2J2 hydroxylated vitamin D(2), an exogenous vitamin D, at a higher rate than it did vitamin D(3), an endogenous vitamin D, whereas, rat CYP2J3 hydroxylated vitamin D(3) (1.4min(-1)) more efficiently than vitamin D(2) (0.86min(-1)). Our study demonstrated that human CYP2J2 exhibits 25-hydroxylation activity as well as rat CYP2J3, although the activity of human CYP2J2 is weaker than rat CYP2J3. CYP2J2 and CYP2J3 exhibit distinct preferences toward vitamin D(3) and D(2).[1]References
- Characterization of rat and human CYP2J enzymes as Vitamin D 25-hydroxylases. Aiba, I., Yamasaki, T., Shinki, T., Izumi, S., Yamamoto, K., Yamada, S., Terato, H., Ide, H., Ohyama, Y. Steroids (2006) [Pubmed]
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