Hanioka Nobumitsu, Naito Takanori, Narimatsu Shizuo
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Chemosphere. 2008 Dec;74(1):33-6. doi: 10.1016/j.chemosphere.2008.09.053. Epub 2008 Nov 5.
Bisphenol A (BPA) is one of a number of potential endocrine disruptors which may affect normal hormonal function. In this study, human UDP-glucuronosyltransferase (UGT) isoforms involved in BPA glucuronidation were studied by kinetic analyses using human liver microsomes and recombinant human UGTs expressed in insect cells (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B4, UGT2B7, UGT2B15 and UGT2B17). BPA glucuronidation was catalyzed by UGT1A1, UGT1A3, UGT1A9, UGT2B4, UGT2B7 and UGT2B15 as well as by human liver microsomes. Among these UGTs, UGT2B15 showed the highest activity of BPA glucuronidation at low- (1.0 microM) and high- (20 microM) substrate concentrations. Kinetic analyses of BPA glucuronidation were performed by constructing Michaelis-Menten and Eadie-Hofstee plots. The kinetic profile of BPA glucuronidation by pooled human liver microsomes and UGT2B15 was monophasic, the K(m) and V(max) values were 6.39 microM and 4250 pmol min(-1)mg(-1)protein for pooled human liver microsomes, and 8.68 microM and 873 pmol min(-1)mg(-1)protein for UGT2B15, respectively. The K(m) values for BPA glucuronidation by pooled human liver microsomes and UGT2B15 were similar. These findings demonstrate that BPA is mainly glucuronidated by UGT2B15 in human liver microsomes, and suggest that this UGT isoform plays important roles in the detoxification and elimination of BPA.
双酚A（BPA）是众多可能影响正常激素功能的潜在内分泌干扰物之一。在本研究中，使用人肝微粒体和在昆虫细胞中表达的重组人尿苷二磷酸葡萄糖醛酸基转移酶（UGT）同工型（UGT1A1、UGT1A3、UGT1A4、UGT1A6、UGT1A9、UGT2B4、UGT2B7、UGT2B15和UGT2B17），通过动力学分析研究了参与BPA葡萄糖醛酸化的人UGT同工型。BPA葡萄糖醛酸化由UGT1A1、UGT1A3、UGT1A9、UGT2B4、UGT2B7和UGT2B15以及人肝微粒体催化。在这些UGT中，UGT2B15在低底物浓度（1.0微摩尔）和高底物浓度（20微摩尔）下表现出最高的BPA葡萄糖醛酸化活性。通过构建米氏方程和伊迪-霍夫斯泰方程曲线对BPA葡萄糖醛酸化进行动力学分析。人肝微粒体混合物和UGT2B15对BPA葡萄糖醛酸化的动力学曲线为单相，人肝微粒体混合物的K(m)和V(max)值分别为6.39微摩尔和4250皮摩尔·分钟(-1)·毫克(-1)蛋白质，UGT2B15的K(m)和V(max)值分别为8.68微摩尔和873皮摩尔·分钟(-1)·毫克(-1)蛋白质。人肝微粒体混合物和UGT2B15对BPA葡萄糖醛酸化的K(m)值相似。这些发现表明，BPA在人肝微粒体中主要由UGT2B15进行葡萄糖醛酸化，提示该UGT同工型在BPA的解毒和消除中起重要作用。
