Physiological role of oligosaccharides present in the first EGF-like domain of clotting factors VII and IX

我们最近在牛因子VII和IX的第一个表皮生长因子样结构域发现了一个新的与丝氨酸53和丝氨酸52相连的三糖链。用几种糖苷酶，α -木糖苷酶，β -木糖苷酶和o-聚糖酶处理牛因子VII和IX，得到无糖蛋白。然而，没有一种酶不能从蛋白质中释放糖链。为了弄清糖链的生理功能，我们合成了包括Glc-Xyl、Glc-Xyl- xyl、Ser-Glc-Xyl和Ser-Glc-Xyl- xyl在内的低聚糖。然而，在磷脂、Ca^<2+>和因子VII存在的情况下，这些低聚糖对因子IXa激活因子X的影响很小或没有影响。此外，在组织因子、磷脂和Ca^<2+ bb0存在的情况下，它们对因子VIIa对因子X的激活没有影响。这些结果表明，在因子VII和因子IX中与egf结构域连接的寡糖并不直接参与外源性凝血途径的激活。

We have found recently a new trisaccharide chain linked to serine 53 and serine 52 located in the first epidermal growth factor-like domain of bovine factors VII and IX.Bovine factors VII and IX were treated with several glycosidases,alpha-xylosidase, beta-xylosidase,and o-glycanase to obtain the sugar-less proteins. None of the enzymes,however,could not release the sugar chains from the proteins. To figure out the physiological function of the sugar chains,we synthesized oligosaccharides including Glc-Xyl,Glc-Xyl-Xyl,Ser-Glc-Xyl, and Ser-Glc-Xyl-Xyl. However,these oligosaccharides had little or no effect on the activation of factor X by factor IXa in the presence of phospholipids,Ca^<2+>,and factor VII. Furthermore,they had no effect on the activation of factor X by factor VIIa in the presence of tissue factor,phospholipids, and Ca^<2+>.These results indicate that the oligosaccharides linked to the EGF-domain in factors VII and IX are not directly involved in the activation of extrinsic coagulation pathway.