Complex formation of human Val354-plasminogen with streptokinase

A controlled digestion of native human plasminogen (Glu1-plasminogen) from either carbohydrate variant 1 or 2 with pancreatic elastase yields, among others, an activatable fragment, designated Val354-plasminogen (Pgc). This species represents the smallest human plasminogen fragment (ca., 50,000 Mw) known to bind to Sepharose-lysine. Pgc forms a tight equimolar complex with streptokinase, as determined by sucrose density ultracentrifugation, whether formed from Val354-plasminogen or Val354-plasmin. The Val354-plasmin-streptokinase complex readily activates ovine plasminogen, which is normally insensitive to streptokinase, and this complex is essentially inactive toward casein, similar to the equimolar complexes formed with Lys77-plasmin and the elastase fragment, Val442-plasmin.