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

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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.