Mackenzie P I
Department of Clinical Pharmacology, School of Medicine, Flinders University of South Australia, Bedford Park.
Biochem Biophys Res Commun. 1990 Feb 14;166(3):1293-9. doi: 10.1016/0006-291x(90)91006-e.
The presence of potential N-linked glycosylation sites (Asn-X-Ser/Thr) in two forms of UDP glucuronosyltransferase, designated UDPGTr-2 and UDPGTr-4, has been deduced from cDNA sequence data. These forms were glycosylated when synthesized from expression vectors transfected into COS cells and were converted to faster migrating species on SDS polyacrylamide gels when treated with endoglycosidase H. The role of glycosylation was investigated by determining the substrate specificities and stabilities of the glycosylated enzymes and their unglycosylated variants which were synthesized in the presence of tunicamycin. Analysis of the activities towards 13 different aglycones showed that the glycosyl moiety was not essential for catalytic activity and had no effect on the substrate preference of each form. The stabilities of the proteins were not adversely affected by the absence of this posttranslational modification. A possible effect of N-linked oligosaccharides on the catalytic properties of these two forms of UDP glucuronosyltransferase is discussed.
根据cDNA序列数据推测，两种形式的UDP葡萄糖醛酸基转移酶（分别命名为UDPGTr - 2和UDPGTr - 4）中存在潜在的N - 糖基化位点（天冬酰胺 - X - 丝氨酸/苏氨酸）。当从转染到COS细胞的表达载体合成这些形式的酶时，它们会发生糖基化，并且在用内切糖苷酶H处理后，在SDS聚丙烯酰胺凝胶上会转化为迁移速度更快的条带。通过测定在衣霉素存在下合成的糖基化酶及其未糖基化变体的底物特异性和稳定性，研究了糖基化的作用。对13种不同糖苷配基的活性分析表明，糖基部分对于催化活性不是必需的，并且对每种形式的底物偏好没有影响。蛋白质的稳定性不受这种翻译后修饰缺失的不利影响。讨论了N - 连接寡糖对这两种形式的UDP葡萄糖醛酸基转移酶催化特性的可能影响。
