Hu Ji-Hong, Wang Li, Li Wan-Shu, Dai Da-Peng, Cai Jian-Ping, Hu Guo-Xin
National Center for Clinical Laboratories, Beijing Hospital, Beijing, PR China.
Pharmacology. 2015;95(5-6):218-23. doi: 10.1159/000381189. Epub 2015 Apr 25.
Mestranol is a widely used estrogen, which is converted into its active metabolite ethinyl estradiol by cytochrome P450 (CYP) 2C9. To comprehensively examine the enzymatic activity of reported CYP2C9 variants in Chinese individuals in response to mestranol, wild-type CYP2C91 and 35 allelic variants were highly expressed in Sf21 insect cell microsomes and used for the detection of their enzymatic values in vitro. These results showed that the majority of tested variants exhibited decreased clearance values compared to wild type, except for CYP2C940 and *36.
Insect microsomes expressing the 36 CYP2C9 variants were incubated with 0.25-8 μmol/l mestranol for 30 min at 37°C. Then, the production of the metabolite of mestranol, ethinyl estradiol, was analyzed using high-performance liquid chromatography.
Most CYP-catalyzed reactions were sufficiently described by classical Michaelis-Menten kinetic parameters (e.g., Km and Vmax), while 9 variants exhibited atypical or non-Michaelis-Menten kinetic values, which were largely due to the self-inhibitory effect in response to mestranol.
This is the first report of these rare alleles for mestranol metabolism, which provides fundamental data for further clinical studies on CYP2C9 alleles for mestranol metabolism.
炔雌醇是一种广泛使用的雌激素，它通过细胞色素P450（CYP）2C9转化为其活性代谢产物乙炔雌二醇。为了全面检测中国个体中已报道的CYP2C9变体对炔雌醇的酶活性，野生型CYP2C91和35个等位基因变体在Sf21昆虫细胞微粒体中高表达，并用于体外检测它们的酶活性值。这些结果表明，除CYP2C940和*36外，大多数测试变体与野生型相比清除率值降低。
将表达36种CYP2C9变体的昆虫微粒体与0.25 - 8 μmol/l炔雌醇在37°C孵育30分钟。然后，使用高效液相色谱法分析炔雌醇的代谢产物乙炔雌二醇的生成。
大多数CYP催化反应可以用经典的米氏动力学参数（如Km和Vmax）充分描述，而9种变体表现出非典型或非米氏动力学值，这在很大程度上是由于对炔雌醇的自抑制作用。
这是关于这些罕见等位基因对炔雌醇代谢的首次报道，为进一步开展关于CYP2C9等位基因对炔雌醇代谢的临床研究提供了基础数据。
