Contributions of Arylacetamide Deacetylase and Carboxylesterase 2 to Flutamide Hydrolysis in Human Liver
Contributions of Arylacetamide Deacetylase and Carboxylesterase 2 to Flutamide Hydrolysis in Human Liver
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DOI：
10.1124/dmd.112.044537
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发表时间：
2012-06-01
影响因子：
3.9
通讯作者：
Yokoi, Tsuyoshi
中科院分区：
文献类型：
--
作者：
Kobayashi, Yuki;Fukami, Tatsuki;Yokoi, Tsuyoshi
氟他胺是一种抗雄激素药物，广泛用于治疗前列腺癌。氟他胺的主要代谢途径是羟基化和水解。水解代谢物5-氨基-2-硝基苯并三氟（flu1）进一步代谢为n -羟基flu1，一种假定的肝毒物。我们之前的研究表明，芳酰乙酰胺脱乙酰酶（AADAC）是人类肝脏和胃肠道中表达的主要丝氨酸酯酶之一，可以催化氟他胺的水解。然而，重组人AADAC在人组织微粒体中的酶动力学与重组人AADAC的酶动力学不一致。因此，AADAC似乎不是人体中唯一负责氟他胺水解的酶。在本研究中，我们发现重组羧酸酯酶（CES） 2可以在低浓度的氟他胺下水解氟他胺。在抑制实验中，氟他胺浓度为5 μ M时，人肝脏和空肠微粒体中氟他胺水解酶活性被选择性CES2抑制剂10 μ M洛哌丁胺强烈抑制，残留活性分别为22.9 +/- 3.5%和18.6 +/- 0.7%。这些结果表明CES2也参与了人体组织中氟他胺的水解。利用6个人肝脏，利用相对活性因子估计了AADAC和CES2对氟他胺水解的贡献。在5 μ M氟他胺浓度下，CES2的相对贡献约为75 ~ 99%。相反，AADAC的相对贡献随氟他胺浓度的增加而增加。因此，在临床治疗中，CES2而不是AADAC在很大程度上促进了氟他胺的水解。
Flutamide, an antiandrogen drug, is widely used for the treatment of prostate cancer. The major metabolic pathways of flutamide are hydroxylation and hydrolysis. The hydrolyzed metabolite, 5-amino-2-nitrobenzotrifluoride (FLU-1), is further metabolized to N-hydroxy FLU-1, an assumed hepatotoxicant. Our previous study demonstrated that arylacetamide deacetylase (AADAC), one of the major serine esterases expressed in the human liver and gastrointestinal tract, catalyzes the flutamide hydrolysis. However, the enzyme kinetics in human tissue microsomes were not consistent with the kinetics by recombinant human AADAC. Thus, it seemed that AADAC is not the sole enzyme responsible for flutamide hydrolysis in human. In the present study, we found that recombinant carboxylesterase (CES) 2 could hydrolyze flutamide at low concentrations of flutamide. In the inhibition assay, the flutamide hydrolase activities at a flutamide concentration of 5 mu M in human liver and jejunum microsomes were strongly inhibited by a selective CES2 inhibitor, 10 mu M loperamide, with the residual activities of 22.9 +/- 3.5 and 18.6 +/- 0.7%, respectively. These results suggest that CES2 is also involved in the flutamide hydrolysis in human tissues. Using six individual human livers, the contributions of AADAC and CES2 to flutamide hydrolysis were estimated by using the relative activity factor. The relative contribution of CES2 was approximately 75 to 99% at the concentration of 5 mu M flutamide. In contrast, the relative contribution of AADAC increased in parallel with the concentration of flutamide. Thus, CES2, rather than AADAC, largely contributed to the flutamide hydrolysis in clinical therapeutics.