Studies on the substrate specificity of human intestinal UDP- lucuronosyltransferases 1A8 and 1A10.
Studies on the substrate specificity of human intestinal UDP- lucuronosyltransferases 1A8 and 1A10.
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发表时间：
1999-10
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通讯作者：
Ziqiang Cheng;A. Radomińska-Pandya;T. R. Tephly
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作者：
Ziqiang Cheng;A. Radomińska-Pandya;T. R. Tephly
虽然肝脏被认为是参与葡萄糖醛酸化的最重要器官，但最近的研究集中在胃肠道在外源性物质和内生性物质的葡萄糖醛酸化中的作用。两个UDP-葡萄糖醛酸基转移酶（UGT）亚型的人肠粘膜，这是缺乏在肝脏中，已被确定的逆转录-聚合酶链反应。在小肠和结肠中均检测到UGT 1A 8和UGT 1A 10的mRNA。从回肠RNA中克隆UGT 1A 8和UGT 1A 10的相应cDNA，并插入哺乳动物表达载体pcDNA 3中。将该cDNA转染人胚肾293细胞，获得稳定表达。分离表达UGT 1A 8或UGT 1A 10的人胚肾293细胞的膜制备物，并通过Western印迹分析每种亚型的表达。稳定表达的UGT 1A 8对儿茶酚类雌激素、香豆素类、黄酮类、蒽醌类和酚类化合物的催化活性远高于UGT 1A 10。UGT 1A 8（而非UGT 1A 10）催化阿片类药物、胆汁酸、脂肪酸、类维生素A和临床有用药物（如环丙贝特、呋塞米和二氟尼柳）的葡萄糖醛酸化。这些研究表明，人类肠道UGT可能在异生物质化合物的解毒中发挥重要作用，并且在某些情况下，限制了治疗剂的生物利用度。
Although the liver has been considered the most important organ involved in glucuronidation, recent studies have focused on the role of the gastrointestinal tract in the glucuronidation of xenobiotics and endobiotics. Two UDP-glucuronosyltransferase (UGT) isoforms of human intestinal mucosa, which are absent in liver, have been identified by reverse transcriptase-polymerase chain reaction. mRNAs of UGT1A8 and UGT1A10 were detected in both the small intestine and the colon. The corresponding cDNAs for UGT1A8 and UGT1A10 were cloned from ileal RNA and inserted into the mammalian expression vector pcDNA3. Transfection of the cDNAs into human embryonic kidney 293 cells was carried out and stable expression was achieved. Membrane preparations from human embryonic kidney 293 cells expressing either UGT1A8 or UGT1A10 were isolated and the expression of each isoform was analyzed by Western blot. The catalytic activity of stably expressed UGT1A8 toward catechol estrogens, coumarins, flavonoids, anthraquinones, and phenolic compounds was much higher than that of UGT1A10. UGT1A8, but not UGT1A10, catalyzed the glucuronidation of opioids, bile acids, fatty acids, retinoids, and clinically useful drugs, such as ciprofibrate, furosemide, and diflunisal. These studies suggest that human intestinal UGTs may play an important role in the detoxification of xenobiotic compounds and, in some cases, limit the bioavailability of therapeutic agents.