Kinetic analyses of the activation of Glu-plasminogen by urokinase in the presence of fibrin, fibrinogen or its degradation products.
The kinetics of the activation of Glu-plasminogen (Glu-plg) and Lys-plasminogen (Lys-plg) by urokinase (UK) were studied in purified systems. The activation of plasminogen by UK in the purified systems followed Michaelis-Menten kinetics with a Michaelis constant (Km) of 1.45 microM and a catalytic rate constant (kcat) of 0.93/sec for Glu-plg as compared to 0.25 microM (Km) and 0.82/sec (kcat) for Lys-plg. In the presence of fibrin and fibrinogen or its plasmin degradation products (fragment D and fragment E), Km for Glu-plg hardly changed, whereas kcat for Glu-plg increased. Effect on increase in kcat was in the order of fibrin greater than fibrinogen greater than D greater than E. Fibrin, fibrinogen, D and E did not influence the activation of Lys-plg by UK. These results indicate that Glu-plg bound to fibrin, fibrinogen, D or E becomes easily activatable by UK. The activation of Lys-plg, however, is not influenced in the presence of fibrin, fibrinogen, D or E.
D004789:Enzyme Activation; D005337:Fibrin / Q000378:metabolism; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D010958:Plasminogen / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism*
D005338:Fibrin Fibrinogen Degradation Products; D005337:Fibrin; D005340:Fibrinogen; D010958:Plasminogen; D014568:Urokinase-Type Plasminogen Activator