EFFECT OF PROTEOLYTIC ENZYMES ON BOVINE FACTOR V .2. KINETICS OF ACTIVATION AND INACTIVATION BY PAPAIN PLASMIN AND OTHER PROTEOLYTIC ENZYMES

The effect of various proteolytic enzymes on the kinetics of activation and inactivation of purified bovine factor V was studied and compared to the effects of thrombin on factor V. Like thrombin, the addition of Russell viper venom to factor V results in a rapid increase in specific activity followed by a slow loss of factor V activity. Human plasma kallikrein, Bothrops jaracara, and Agkistrodon rhodostoma venom have no effect on factor V. Plasmin and trypsin destroy this plasma protein, a process inhibited by soybean trypsin inhibitor. Papain is unique in activating factor V at low concentrations, a reaction inhibited by iodoacetate, and destroying it at higher concentrations. Each of these proteolytic enzymes was examined to ascertain its effect on the course of thrombin activation and inactivation. Russell viper venom and trypsin do not interfere with thrombin action of factor V, but papain directly inhibits thrombin activation of factor V by successful competition for thrombin-susceptible bonds. Plasmin decreases the extent of activity increase catalyzed by thrombin by increasing the rate of inactivation of thrombin-altered factor V. © 1969, American Chemical Society. All rights reserved.