Simultaneous expression of guinea pig UDP-glucuronosyltransferase 2B21 and 2B22 in COS-7 cells enhances UDP-glucuronosyltransferase 2B21-catalyzed morphine-6-glucuronide formation
Simultaneous expression of guinea pig UDP-glucuronosyltransferase 2B21 and 2B22 in COS-7 cells enhances UDP-glucuronosyltransferase 2B21-catalyzed morphine-6-glucuronide formation
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DOI：
10.1124/mol.60.5.1040
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发表时间：
2001-11-01
影响因子：
3.6
通讯作者：
Oguri, K
中科院分区：
文献类型：
--
作者：
Ishii, Y;Miyoshi, A;Oguri, K
UDP-葡萄糖醛酸转移酶（UGT）是许多内源性和外源性化合物的重要解毒系统，但也参与吗啡代谢活化形成吗啡-6-葡萄糖醛酸苷（M-6-G）。编码豚鼠肝UGT 2B 21和UGT 2B 22的cDNA已被克隆和表征，它们与M-6-G形成密切相关。尽管一些证据表明UGT可能作为寡聚体发挥作用，但尚不清楚异源寡聚体的形成是否导致底物特异性的差异。在这项工作中，UGT 2B 21和UGT 2B 22之间的功能性异源寡聚体的证据是通过对转染的COS-7细胞中吗啡的葡萄糖醛酸化的研究提供的。转染UGT 2B 21 cDNA的细胞主要催化吗啡-3-葡萄糖醛酸苷的形成，但也在一定程度上形成M-6-G。相反，用UGT 2B 22 cDNA转染的细胞没有显示出对吗啡的任何显著活性。当UGT 2B 21和UGT 2B 22在COS-7细胞中以不同比例同时表达时，观察到广泛的M-6-G形成。然而，当含有UGT 2B 21的微粒体与含有UGT 2B 22的微粒体在存在去污剂的情况下混合时，未观察到对M-6-G形成的刺激。此外，当人UGT 1A 1和UGT 2B 21在COS-7细胞中共表达时，这种作用并不十分显著。这是第一份报告表明，UGT异源寡聚体的形成导致改变底物特异性。
Although UDP-glucuronosyltransferases (UGTs) act as an important detoxification system for many endogenous and exogenous compounds, they are also involved in the metabolic activation of morphine to form morphine-6-glucuronide (M-6-G). The cDNAs encoding guinea pig liver UGT2B21 and UGT2B22, which are intimately involved in M-6-G formation, have been cloned and characterized. Although some evidence suggests that UGTs may function as oligomers, it is not known whether hetero-oligomer formation leads to differences in substrate specificity. In this work, evidence for a functional heterooligomer between UGT2B21 and UGT2B22 is provided by studies on the glucuronidation of morphine in transfected COS-7 cells. Cells transfected with UGT2B21 cDNA catalyzed mainly morphine-3-glucuronide formation although M-6-G was also formed to some extent. In contrast, cells transfected with UGT2B22 cDNA did not show any significant activity toward morphine. When UGT2B21 and UGT2B22 were expressed simultaneously in different ratios in COS-7 cells, extensive M-6-G formation was observed. This stimulation of M-6-G formation was not observed, however, when microsomes containing UGT2B21were mixed with those containing UGT2B22 in the presence of detergent. Furthermore, this effect was not very marked when human UGT1A1 and UGT2B21 were coexpressed in COS-7 cells. This is the first report suggesting that UGT hetero-oligomer formation leads to altered substrate specificity.