Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Basic Clin Pharmacol Toxicol. 2010 Jul;107(1):565-9. doi: 10.1111/j.1742-7843.2010.00543.x. Epub 2010 Feb 10.
Cytochrome P450 2C8 (CYP2C8) plays important roles in the metabolism of various drugs, including the anti-cancer drug, paclitaxel. We recently identified two novel CYP2C8 alleles (CYP2C813 and CYP2C814; wild-type, CYP2C81A) with non-synonymous single nucleotide polymorphisms in a Japanese population. To precisely investigate the effect of amino acid substitutions (CYP2C813, Ile223Met; CYP2C814, Ala238Pro) on CYP2C8 function, CYP2C8 proteins of the wild-type (CYP2C8.1) and variants (CYP2C8.13 and CYP2C8.14) were heterologously expressed in yeast cells, and their paclitaxel 6alpha-hydroxylation activities were determined. The K(m), V(max) and CL(int) values for paclitaxel 6alpha-hydroxylation of CYP2C8.1 were 2.3 microM, 4.1 pmol/min./pmol CYP and 1.7 microl/min./pmol CYP, respectively. The K(m) value of CYP2C8.14 was significantly higher (2.9-fold) than that of CYP2C8.1. The V(max) value of CYP2C8.14 was comparable to that of CYP2C8.1 and the CL(int) value was reduced to 46% of CYP2C8.1. In contrast, the K(m), V(max) and CL(int) values of CYP2C8.13 were similar to those of CYP2C8.1. These results suggest that Ala238Pro substitution in CYP2C8.14 decreases the affinity toward paclitaxel of the CYP2C8 enzyme, and that the genetic polymorphism of the CYP2C814 allele may influence the clinical response to drugs metabolized mainly by CYP2C8.
细胞色素 P450 2C8（CYP2C8）在各种药物的代谢中发挥重要作用，包括抗癌药物紫杉醇。我们最近在日本人群中发现了两种新型 CYP2C8 等位基因（CYP2C813 和 CYP2C814；野生型，CYP2C81A），它们具有非同义单核苷酸多态性。为了准确研究氨基酸取代（CYP2C813，Ile223Met；CYP2C814，Ala238Pro）对 CYP2C8 功能的影响，我们在酵母细胞中异源表达了野生型（CYP2C8.1）和变体（CYP2C8.13 和 CYP2C8.14）的 CYP2C8 蛋白，并测定了它们对紫杉醇 6α-羟化的活性。CYP2C8.1 对紫杉醇 6α-羟化的 K(m)、V(max)和 CL(int)值分别为 2.3 μM、4.1 pmol/min./pmol CYP 和 1.7 μl/min./pmol CYP。CYP2C8.14 的 K(m)值显著升高（2.9 倍）。CYP2C8.14 的 V(max)值与 CYP2C8.1 相当，CL(int)值降至 CYP2C8.1 的 46%。相比之下，CYP2C8.13 的 K(m)、V(max)和 CL(int)值与 CYP2C8.1 相似。这些结果表明，CYP2C8.14 中的 Ala238Pro 取代降低了 CYP2C8 酶对紫杉醇的亲和力，CYP2C814 等位基因的遗传多态性可能影响主要由 CYP2C8 代谢的药物的临床反应。
