INHIBITORY POTENCY OF ERYTHRINA-VARIEGATA PROTEINASE-INHIBITORS TOWARD SERINE PROTEINASES IN THE BLOOD-COAGULATION AND FIBRINOLYTIC SYSTEMS

The Erythrina variegata Kunitz family trypsin inhibitors, ETIa and ETI b, prolonged the activated partial thromboplastin time (APTT) and also the prothrombin time (PT) of human plasma, but the Kunitz family chym otrypsin inhibitor, ECI, and Bowman-Birk family inhibitor, EBI, from E . variegata hardly prolonged these times. Trypsin inhibitors ETIa and ETIb inhibited the amidolytic activity of factor Xa, and ETIb but not ETIa inhibited plasma kallikrein. Neither Ena nor ETIb exhibited any i nhibitory activity toward beta-factor XIIa and thrombin. Furthermore, trypsin inhibitors ETIa and ETIb inhibited plasmin, a serine proteinas e in the fibrinolytic system, whereas ECI and EBI did not. These resul ts indicate that Erythrina Kunitz proteinase inhibitors possess differ ent potency toward serine proteinases in the blood coagulation and fib rinolytic systems, in spite of their high similarity in amino acid seq uence.