Purification and characterization of a variant of human prothrombin: prothrombin Segovia.

A dysprothrombin designated prothrombin Segovia was isolated from the plasma of an individual with normal prothrombin antigen and prothrombin activity lesser than 25% of the control prothrombin activity. Activation by prothrombinase complex showed a lower amidolytic than clotting activity, which suggests a lesser generation of active intermediates than normal prothrombin. When prothrombin Segovia was activated by prothrombinase complex in the absence of factor Va, no thrombin formation was found by functional activities. SDS-PAGE analysis of the molecules derived by activation with prothrombinase complex, Taipan snake venom and Echis carinatus venom showed an accumulation of molecules not cleaved at bond Arg320-Ile321. This was more evident with Echis carinatus venom, which only acts on this bond. Our data suggest that the alteration of prothrombin Segovia impairs the scission of bond Arg320-Ile321.