[Activation of the anticoagulant system by prethrombin 2, a thrombin precursor]

Prethrombin 2, and immediate precursor of thrombin, was obtained by limited trypsin or active factor X proteolysis by prethrombin 1. The conversion of prethrombin 1 to prethrombin 2 does not occur in the absence of enzymes. It has been shown that factor V has no influence on the rate of thrombin generation from prethrombin 2 and that prethrombin itself has no coagulant or esterase activity. Intravenous injection of prethrombin 2 preparations led to an increase in plasma recalcification time, overall fibrinolytic activity and non-enzymatic fibrinolysis. In addition, there was observed a considerable increase in fibrinogen-heparin complex activity. The data obtained indicate excitation of the anticoagulant system with intravenous injection of small doses of prethrombin 2.