Fibrinolysis and fibrinogenolysis by Val442-plasmin

Elastase cleavage of Lys77-plasmin results in the formation of Val442-plasmin. This result suggests that small, active plasmin fragments can be produced even under conditions of high plasminogen activator levels such as occur in vivo. We examined the effect of the generation of such fragments by studying the degradation of fibrinogen and fibrin by Val442-plasmin. Val442-plasmin lysis of fibrinogen yielded the same products as obtained with Lys77-plasmin, but at a slightly lower rate. Lysine inhibited fibrinogenolysis by both Lys77-plasmin and Val442-plasmin. The marked inhibition observed at concentrations higher than 10 mM lysine occurred to the same extent for both proteases. In addition, the products and rate of fibrinolysis were the same for both proteases. These results indicate that the lysine binding regions present in Lys77-plasmin but absent in Val442-plasmin do not determine the rate, reaction products, or lysine inhibition of fibrinolysis and fibrinogenolysis by plasmin.