Fibrin suspension as a substrate fop plasmin: determination and kinetics

Fibrin polymers formed from fibrinogen with thrombin in the presence of EDTA were suspended in a medium containing glucose, arabic gum and imidazole-HCl buffer and were sonicated at 20 kHz for 20 min to make a suspension containing fibrin particles of small size. The fibrin suspension was used as a substrate of plasmin for determining the enzymic activity of plasmin and plasminogen activated with urokinase. The kinetic study on the reaction of the fibrin particles with plasmin in the presence and the absence of fibrinogen revealed that Km value of fibrin for plasmin is 4.2 x 10(-7) M and the Ki value of fibrinogen is 1.2 x 10(-5) M.