Investigations Concerning the Protaminase Activity of Serum and Plasma

Abstract

In previous investigations concerning the ability of serum to dissolve crystals of protamine insulin it was concluded that plasmin was the only protaminase. Nephelometric methods of measurements of the speed of destruction of the crystals were employed partly to measure the fibrinolytic activity of the blood. The present work consists of further investigations concerning the protaminase activity in plasma, serum, and euglobulin fractions from human and bovine blood, with and without activation by streptokinase and urokinase. It is established that the spontaneous protaminase activity of the blood is due to unclassified proteases and only to a sligt extent to plasmin, if any. The protaminase activity after activation with streptokinase in blood is an expression of the content of plasminogen in the blood; the effect of inhibitor, however, cannot be evaluated. In parallel determinations of the protaminase activity and fibrinolytic activity on the same plasma and euglobulin, it is demonstrated that there is no connection between the two forms of activity. The protaminase activity cannot, thus, be employed as a measurement of the fibrinolytic activity of plasma.