The Novel UDP Glycosyltransferase 3A2: Cloning, Catalytic Properties, and Tissue Distribution
作者:Peter I. MacKenzie、Anne Rogers、David J. Elliot、Nuy Chau、Julie-Ann Hulin、John O. Miners、Robyn Meech
DOI:10.1124/mol.110.069336
日期:2011.3
The human UDP glycosyltransferase (UGT) 3A family is one of three families involved in the metabolism of small lipophilic compounds. Members of these families catalyze the addition of sugar residues to chemicals, which enhances their excretion from the body. The UGT1 and UGT2 family members primarily use UDP glucuronic acid to glucuronidate numerous compounds, such as steroids, bile acids, and therapeutic drugs. We showed recently that UGT3A1, the first member of the UGT3 family to be characterized, is unusual in using UDP N -acetylglucosamine as sugar donor, rather than UDP glucuronic acid or other UDP sugar nucleotides ( J Biol Chem 283: 36205–36210, 2008). Here, we report the cloning, expression, and characterization of UGT3A2, the second member of the UGT3 family. Like UGT3A1, UGT3A2 is inactive with UDP glucuronic acid as sugar donor. However, in contrast to UGT3A1, UGT3A2 uses both UDP glucose and UDP xylose but not UDP N -acetylglucosamine to glycosidate a broad range of substrates including 4-methylumbelliferone, 1-hydroxypyrene, bioflavones, and estrogens. It has low activity toward bile acids and androgens. UGT3A2 transcripts are found in the thymus, testis, and kidney but are barely detectable in the liver and gastrointestinal tract. The low expression of UGT3A2 in the latter, which are the main organs of drug metabolism, suggests that UGT3A2 has a more selective role in protecting the organs in which it is expressed against toxic insult rather than a more generalized role in drug metabolism. The broad substrate and novel UDP sugar specificity of UGT3A2 would be advantageous for such a function.
人UDP-葡萄糖基转移酶(UGT)3A家族是涉及小脂溶性化合物代谢的三个家族之一。这些家族的成员催化糖残基添加到化学物质上,从而增强它们的排泄。UGT1和UGT2家族成员主要使用UDP-葡萄糖醛酸来糖苷化许多化合物,如类固醇、胆汁酸和治疗药物。我们最近表明,UGT3A1是第一个被表征的UGT3家族成员,它使用UDP N-乙酰葡萄糖胺作为糖供体,而不是UDP-葡萄糖醛酸或其他UDP糖核苷酸(J Biol Chem 283: 36205-36210, 2008)。在这里,我们报告了UGT3A2的克隆、表达和表征,UGT3A2是UGT3家族的第二个成员。与UGT3A1一样,UGT3A2在使用UDP-葡萄糖醛酸作为糖供体时无活性。然而,与UGT3A1不同,UGT3A2使用UDP葡萄糖和UDP木糖,但不使用UDP N-乙酰葡萄糖胺来糖苷化包括4-甲基伞形酮、1-羟基芘、生物类黄酮和雌激素在内的广泛底物。它对胆汁酸和雄激素的活性较低。UGT3A2的转录本存在于胸腺、睾丸和肾脏中,但在肝脏和胃肠道中几乎检测不到。UGT3A2在后者的主要器官中低表达,表明UGT3A2在这些器官中发挥选择性保护作用,抵御毒性损害,而不是在药物代谢中发挥更普遍的作用。UGT3A2广泛的底物和新颖的UDP糖特异性将有利于这种功能。