Characterization of the Zebrafish<i>Ugt</i>Repertoire Reveals a New Class of Drug-Metabolizing UDP Glucuronosyltransferases
作者:Yuanming Wang、Haiyan Huang、Qiang Wu
DOI:10.1124/mol.113.091462
日期:2014.7
The zebrafish genome contains a gene superfamily of 40 Ugt genes that can be divided into Ugt1 , Ugt2 , and Ugt5 families. Because the encoded zebrafish UDP glucuronosyltransferase (UGT) proteins do not display orthologous relationships to any of the mammalian and avian UGT enzymes based on molecular phylogeny, it is difficult to predict their substrate specificity. Here, we mapped their tissue-specific expression patterns. We showed that the zebrafish UGT enzymes can be glycosylated. We determined their substrate specificity and catalytic activity toward diverse aglycone substrates. Specifically, we measured mRNA levels of each of the 40 zebrafish Ugt genes in 11 adult tissues and found that they are expressed in a tissue-specific manner. Moreover, functional analyses with the donor of UDP glucuronic acid (UDPGA) for each of the 40 zebrafish UGT proteins revealed their substrate specificity toward 10 important aglycones. In particular, UGT1A1, UGT1A7, and UGT1B1 displayed good glucuronidation activities toward most phenolic aglycones (4-methylumbelliferone, 4-nitrophenol, 1-naphthol, bisphenol A, and mycophenolic acid) and the two carboxylic acids (bilirubin and diclofenac). Importantly, some members of the UGT5, a novel UGT family identified recently, are capable of glucuronidating multiple aglycones with the donor cofactor of UDPGA. In particular, UGT5A5, UGT5B2, and UGT5E1 glucuronidate phenols and steroids with high specificity toward steroid hormones of estradiol and testosterone and estrogenic alkylphenols 4- tert -octylphenol. These results shed new insights into the mechanisms by which fish species defend themselves against vast numbers of xenobiotics via glucuronidation conjugations and may facilitate the establishment of zebrafish as a model vertebrate in toxicological, developmental, and pathologic studies.
斑马鱼基因组含有一个由40个Ugt基因组成的超家族,这些基因可以被分为Ugt1、Ugt2和Ugt5家族。由于编码的斑马鱼尿苷二磷酸葡萄糖醛酸转移酶(UGT)蛋白在分子系统发育上与任何哺乳动物和鸟类的UGT酶都不显示直系同源关系,因此难以预测它们的底物特异性。在这里,我们绘制了它们的组织特异性表达模式。我们展示了斑马鱼UGT酶可以进行糖基化。我们确定了它们对多种配基底物的底物特异性和催化活性。具体来说,我们在11种成体组织中测量了每个40个斑马鱼Ugt基因的mRNA水平,并发现它们以组织特异性的方式表达。此外,通过每个40个斑马鱼UGT蛋白的供体尿苷二磷酸葡萄糖醛酸(UDPGA)的功能分析揭示了它们对10种重要配基的底物特异性。特别是,UGT1A1、UGT1A7和UGT1B1对大多数酚类配基(4-甲基伞形酮、4-硝基苯酚、1-萘酚、双酚A和霉酚酸)和两种羧酸(胆红素和双氯芬酸)显示出良好的葡萄糖醛酸化活性。重要的是,最近鉴定出的新型UGT家族UGT5的一些成员能够通过UDPGA供体辅因子葡萄糖醛酸化多种配基。特别是,UGT5A5、UGT5B2和UGT5E1对酚类和类固醇具有高度特异性,对雌二醇和睾酮等类固醇激素和4-叔辛基苯酚等雌激素性烷基酚进行高度特异性的葡萄糖醛酸化。这些结果为通过葡萄糖醛酸化缀合物防御大量外源性物质的机理提供了新的见解,并可能有助于将斑马鱼确立为毒理学、发育学和病理学研究中的模型脊椎动物。