School of Pharmacy, Shujitsu University, 1-6-1 Nishigawara, Naka-ku, Okayama, 703-8516, Japan.
School of Pharmacy, Shujitsu University, 1-6-1 Nishigawara, Naka-ku, Okayama, 703-8516, Japan.
Arch Biochem Biophys. 2020 Mar 30;682:108283. doi: 10.1016/j.abb.2020.108283. Epub 2020 Jan 27.
Hydroxylation activity at the 6β-position of steroid hormones (testosterone, progesterone, and cortisol) by human cytochromes P450 (CYP) 3A4, polymorphic CYP3A5, and fetal CYP3A7 were compared to understand the catalytic properties of the major forms of human CYP3A subfamily. Testosterone, progesterone, and cortisol 6β-hydroxylation activities of recombinant CYP3A4, CYP3A5, and CYP3A7 were determined by liquid chromatography. Michaelis constants (K) for CYP3A7-mediated 6β-hydroxylation of testosterone, progesterone, and cortisol were similar to those of CYP3A4 and CYP3A5. The maximal velocity (k) and k/K values for CYP3A4 were the highest, followed by CYP3A5 and those for CYP3A7 were the lowest among three CYP3A subfamily members. A decrease in K values for progesterone 6β-hydroxylation by CYP3A4, CYP3A5, and CYP3A7 in the presence of testosterone was observed, and the k values for CYP3A5 gradually increased with increasing testosterone. This indicated that testosterone stimulated progesterone 6β-hydroxylation by all three CYP3A subfamily members. However, progesterone inhibited testosterone 6β-hydroxylation mediated by CYP3A4, CYP3A5, and CYP3A7. In conclusion, the k values, rather than K values, for 6β-hydroxylation of three steroid hormones mediated by CYP3A7 were different from those for CYP3A4 and CYP3A5. In addition, the inhibitory/stimulatory pattern of steroid-steroid interactions would be different among CYP3A subfamily members.
比较了人细胞色素 P450（CYP）3A4、多态性 CYP3A5 和胎儿 CYP3A7 对甾体激素（睾酮、孕酮和皮质醇）6β-位的羟化活性，以了解人 CYP3A 亚家族主要形式的催化特性。采用液相色谱法测定重组 CYP3A4、CYP3A5 和 CYP3A7 介导的睾酮、孕酮和皮质醇 6β-羟化活性。CYP3A7 介导的睾酮、孕酮和皮质醇 6β-羟化的米氏常数（K）与 CYP3A4 和 CYP3A5 的相似。CYP3A4 的最大速度（k）和 k/K 值最高，其次是 CYP3A5，而 CYP3A7 的最低。在睾酮存在下，CYP3A4、CYP3A5 和 CYP3A7 介导的孕酮 6β-羟化的 K 值降低，而 CYP3A5 的 k 值随着睾酮的增加而逐渐增加。这表明睾酮刺激所有三种 CYP3A 亚家族成员的孕酮 6β-羟化。然而，孕酮抑制 CYP3A4、CYP3A5 和 CYP3A7 介导的睾酮 6β-羟化。总之，与 CYP3A4 和 CYP3A5 相比，CYP3A7 介导的三种甾体激素 6β-羟化的 k 值而不是 K 值不同。此外，甾体-甾体相互作用的抑制/刺激模式在 CYP3A 亚家族成员之间会有所不同。
