FIBRINOGENOLYTIC EFFECT OF ECARIN - PROTHROMBIN CONVERTING ENZYME

Purified bovine and human fibrinogen incubated with a prothrombin converting enzyme isolated from the venom of Echis carinata gradually loses the ability to be converted to fibrin by thrombin. The amount of unclottable protein in the supernate increases simultaneously with the prolongation of the clotting time. Split products obtained following 10 min to 9 hours of digestion were analyzed by SDS polyacrylamide gel electrophoresis. A fragment of m.w. 280,000 within 15 min of digestion is produced. Electrophoretic patterns of samples reduced by β mercaptoethanol show that Ecarin hydrolyzes the α A chain first, β B chain is digested more slowly. A degradation product of m.w. 25,000 can be detected after 30 min of digestion, in later phases - after 9 hours - second band of m.w. 32,000 appears. Both peptides are bound to the maternal molecule by disulfide bonds. From the course of the digestion and from the structural changes in the fibrinogen molecule it is concluded that Ecarin attacks primarily the carboxy-terminal end of α A chain. Effective polymerization is impaired in the earlier phases of the enzyme-substrate reaction. The proteolysis of fibrinogen by Ecarin follows a different pattern than that produced by plasmin. © 1979.