Abstract
Comparison of three synthetic substrates, S-2251 (H-D-Val-Leu-Lys-pNA), TLMe (tosyl lysine methyl ester), TAMe (tosyl arginine methyl ester) was done with respect to substrate specificity for thrombin, urokinase (UK), UK-activated plasmin, and kaolin-activated plasma (kallikrein). TLMe was hydrolyzed by thrombin and to a lesser extent by plasmin, and TAMe was hydrolyzed by thrombin and to a lesser extent by plasmin and kaolin-activated plasma. S-2251 was very specific to plasmin. The hydrolysis of S-2251 by plasma in the presence of UK and SK (streptokinase) was higher when clot was formed by the addition of thrombin than in the absence of clot. The hydrolysis of S-2251 by euglobulin in the presence of UK was also higher when clot was formed, thus, inhibitors may not be related to the better activation of plasminogen in the presence of fibrin clot. It may be suggested that plasminogen was better activated by activators in the clot than in its absence. Acid treated plasminogen (mainly Lys-plasminogen) was not better activated by UK in the clot compared to the activation in the plasma.
