Generation of proteolytic activity during activation of prothrombin

Abstract

In the activation of purified prothrombin with thrombin, with platelet factor 3, or in 25% sodium citrate solution the free thrombin activity which develops is greater at all times when measured by hydrolysis of p-toluenesulfonyl-arginine-methyl ester than when measured by the clotting of fibrinogen. Since the esterase activity appears before clotting power and remains after clotting power is lost, the clotting property must arise from a dissociable complex arising from the unit that has the esterase function. It is postulated that "clotting thrombin" may be a dimer of the lowest subunit of prothrombin required to have the proteolytic enzyme. The latter could have an important function in our physiology quite apart from the clotting of blood.