Aiba Isamu, Yamasaki Tomoaki, Shinki Toshimasa, Izumi Shunsuke, Yamamoto Keiko, Yamada Sachiko, Terato Hiroaki, Ide Hiroshi, Ohyama Yoshihiko
Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
Steroids. 2006 Oct;71(10):849-56. doi: 10.1016/j.steroids.2006.04.009. Epub 2006 Jul 13.
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 D3 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 D3 (turnover number, 0.087 min(-1)), vitamin D2 (0.16 min(-1)), and 1alpha-hydroxyvitamin D3 (2.2 min(-1)). Interestingly, human CYP2J2 hydroxylated vitamin D2, an exogenous vitamin D, at a higher rate than it did vitamin D3, an endogenous vitamin D, whereas, rat CYP2J3 hydroxylated vitamin D3 (1.4 min(-1)) more efficiently than vitamin D2 (0.86 min(-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 D3 and D2.
维生素D先在肝脏中进行25-羟化，然后在肾脏中通过1α-羟化被激活。最近，大鼠细胞色素P450 2J3（CYP2J3）已被确定为大鼠体内主要的维生素D 25-羟化酶[山崎T，泉S，井出H，大山Y。新型大鼠微粒体维生素D3 25-羟化酶的鉴定。《生物化学杂志》2004年；279(22):22848 - 56]。在本研究中，我们检测与大鼠CYP2J3具有73%氨基酸同源性的人CYP2J2是否具有相似的催化特性。重组人CYP2J2在大肠杆菌中过表达、纯化，并检测其维生素D 25-羟化活性。我们发现其对维生素D3（转换数，0.087 min⁻¹）、维生素D2（0.16 min⁻¹）和1α-羟基维生素D3（2.2 min⁻¹）具有显著的25-羟化活性。有趣的是，人CYP2J2对外源性维生素D2的羟化速率高于内源性维生素D3，而大鼠CYP2J3对维生素D3（1.4 min⁻¹）的羟化效率高于维生素D2（0.86 min⁻¹）。我们的研究表明，人CYP2J2与大鼠CYP2J3一样具有25-羟化活性，尽管人CYP2J2的活性比大鼠CYP2J3弱。CYP2J2和CYP2J3对维生素D3和D2表现出不同的偏好。
