Effect of glycosidase treatment of factor V on its activation by thrombin. Factor V was preincubated with neuraminidase plus N-glycanase according to the Materials and Methods and then activated by thrombin. The time course of activation of factor V treated with glycosidases was followed (○) and compared with the control nontreated factor V (•). Factor Va procoagulant activity was determined in PT assays using factor V-deficient plasma and expressed relative to the activity of single-chain factor V that was not activated by thrombin.