Regioselective metabolism of taxoids by human CYP3A4 and 2C8: Structure-activity relationship
Regioselective metabolism of taxoids by human CYP3A4 and 2C8: Structure-activity relationship
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DOI：
10.1124/dmd.30.4.438
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发表时间：
2002-04-01
影响因子：
3.9
通讯作者：
Gueritte, F
中科院分区：
文献类型：
--
作者：
Cresteil, T;Monsarrat, B;Gueritte, F
紫杉醇和多西紫杉醇通过肝脏微粒体单加氧酶代谢成不活跃的代谢物，通过胆汁途径进一步从体内清除。尽管它们的化学结构很接近，但这两种药物被两种不同的酶氧化：CYP2C8催化紫杉醇的紫杉烷环上的6-羟基化，而CYP3A4氧化C13侧链上的叔丁基上的多西紫杉醇。由于紫杉醇和多西紫杉醇只有两个取代位不同，因此我们研究了单独修饰的作用；用高压液相色谱/质谱仪评估了羟化的区域选择性，并利用人肝微粒体和在AD293细胞中表达的重组P450鉴定了参与个别反应的酶。多西紫杉醇、110-脱乙酰基紫杉醇和10-脱乙酰基巴卡菌素III的生物转化率通过在第10位增加一个乙酰基稳步提高(2-5倍)，这表明第10位的疏水基团的存在刺激了P450蛋白的羟化。巴卡菌素III中C13侧链的缺失严重损害了细胞色素P3A4所支持的代谢。多西紫杉醇侧链上叔丁基团的存在有利于CYP3A4在叔丁基上的羟基化反应，而侧链上苯基的存在有利于CYP2C8在紫杉烷环上的氧化反应。综上所述，这些数据有力地表明，侧链的结构和第10位取代基的性质在决定P450蛋白的区域选择性氧化和调节人肝微粒体的反应速度方面发挥着重要作用。
Paclitaxel and docetaxel are metabolized by liver microsomal monooxygenases into inactive metabolites further eliminated from the body via the bile route. In spite of their close chemical structure, the two drugs are oxidized by two different enzymes; CYP2C8 catalyzes the 6-hydroxylation on the taxane ring of paclitaxel, whereas CYP3A4 oxidizes docetaxel on the tert-butyl group of the lateral chain in C13. Since paclitaxel and docetaxel differ only by two substitutions, the role of individual modifications was investigated; the regioselectivity of hydroxylation was assessed by high-pressure liquid chromatography/mass spectrometry, and enzymes implicated in individual reactions were identified using human liver microsomes and recombinant P450 expressed in Ad293 cells. The biotransformation of docetaxel, 110-deacetylpaclitaxel, and 10-deacetylbaccatin III was steadily increased (2- to 5-fold) by the addition of an acetyl group in position 10, suggesting that the presence of a hydrophobic group in position 10 stimulated hydroxylation by P450 proteins. The absence of the lateral chain at C13 in baccatin III severely impaired the metabolism supported by CYP3A4. The presence of a tert-butyl group in the lateral chain of docetaxel favored the hydroxylation on the tert-butyl by CYP3A4, whereas the presence of a phenyl group in the lateral chain facilitated the oxidation on the taxane ring by CYP2C8. Collectively, these data strongly suggested that the structure of the lateral chain and the nature of substituent in position 10 play an important role in determining the regioselective oxidation by P450 proteins and modulate the reaction rate by human liver microsomes.