[Kinetic characteristics of the activation of various structural forms of plasminogen by tissue activator in the presence of fibrin].

It was shown that activation of two native plasminogen and miniplasminogen forms by the tissue activator in the presence of fibrin obeys the Michaelis-Menten kinetics. The kinetic parameters of activation of both plasminogen native forms differ insignificantly. For miniplasminogen whose molecule contains no lysine-binding sites, a marked decrease of activation power was observed. The Km value of activator for miniplasminogen is 10 times that of plasminogen form I and 20 times that of plasminogen form II. The kcat/Km value of activator for miniplasminogen is 7 times less than that of plasminogen form I and by one order of magnitude more than that of plasminogen form II. These results testify to the importance of lysine-binding sites in the native plasminogen molecule during the activation of fibrinolysis by the major physiological activator.