Jeurissen Suzanne M F, Punt Ans, Boersma Marelle G, Bogaards Jan J P, Fiamegos Yiannis C, Schilter Benoit, van Bladeren Peter J, Cnubben Nicole H P, Rietjens Ivonne M C M
Division of Toxicology, Wageningen University, Tuinlaan 5, 6703 HE Wageningen, The Netherlands.
Chem Res Toxicol. 2007 May;20(5):798-806. doi: 10.1021/tx700012d. Epub 2007 Apr 4.
Human cytochrome P450 enzymes involved in the bioactivation of estragole to its proximate carcinogen 1'-hydroxyestragole were identified and compared to the enzymes of importance for 1'-hydroxylation of the related alkenylbenzenes methyleugenol and safrole. Incubations with Supersomes revealed that all enzymes tested, except P450 2C8, are intrinsically able to 1'-hydroxylate estragole. Experiments with Gentest microsomes, expressing P450 enzymes to roughly average liver levels, indicated that P450 1A2, 2A6, 2C19, 2D6, and 2E1 might contribute to estragole 1'-hydroxylation in the human liver. Especially P450 1A2 is an important enzyme based on the correlation between P450 1A2 activity and estragole 1'-hydroxylation in human liver microsomal samples and inhibition of estragole 1'-hydroxylation by the P450 1A2 inhibitor alpha-naphthoflavone. Kinetic studies revealed that, at physiologically relevant concentrations of estragole, P450 1A2 and 2A6 are the most important enzymes for bioactivation in the human liver showing enzyme efficiencies (kcat/Km) of, respectively, 59 and 341 min-1 mM-1. Only at relatively high estragole concentrations, P450 2C19, 2D6, and 2E1 might contribute to some extent. Comparison to results from similar studies for safrole and methyleugenol revealed that competitive interactions between estragole and methyleugenol 1'-hydroxylation and between estragole and safrole 1'-hydroxylation are to be expected because of the involvement of, respectively, P450 1A2 and P450 2A6 in the bioactivation of these compounds. Furthermore, poor metabolizer phenotypes in P450 2A6 might diminish the chances on bioactivation of estragole and safrole, whereas lifestyle factors increasing P450 1A2 activities such as cigarette smoking and consumption of charbroiled food might increase those chances for estragole and methyleugenol.
鉴定了参与将草蒿脑生物活化成其直接致癌物1'-羟基草蒿脑的人细胞色素P450酶，并将其与对相关链烯基苯甲基丁香酚和黄樟素的1'-羟基化起重要作用的酶进行比较。用Supersomes进行的孵育表明，除P450 2C8外，所有测试的酶本质上都能够将草蒿脑1'-羟基化。用表达P450酶至大致平均肝脏水平的Gentest微粒体进行的实验表明，P450 1A2、2A6、2C19、2D6和2E1可能在人肝脏中对草蒿脑1'-羟基化有贡献。基于人肝微粒体样品中P450 1A2活性与草蒿脑1'-羟基化之间的相关性以及P450 1A2抑制剂α-萘黄酮对草蒿脑1'-羟基化的抑制作用，P450 1A2尤其重要。动力学研究表明，在草蒿脑的生理相关浓度下，P450 1A2和2A6是人体肝脏中生物活化的最重要酶，酶效率（kcat/Km）分别为59和341 min-1 mM-1。仅在相对较高的草蒿脑浓度下，P450 2C19、2D6和2E1可能在一定程度上起作用。与黄樟素和甲基丁香酚的类似研究结果比较表明，由于P450 1A2和P450 2A6分别参与这些化合物的生物活化，预计草蒿脑与甲基丁香酚1'-羟基化之间以及草蒿脑与黄樟素1'-羟基化之间会存在竞争性相互作用。此外，P450 2A6中的代谢不良表型可能会降低草蒿脑和黄樟素生物活化的机会，而增加P450 1A2活性的生活方式因素，如吸烟和食用烤焦食物，可能会增加草蒿脑和甲基丁香酚生物活化的机会。
