THE ACTIVATION OF PLASMINOGEN BY T-PA-PAI-1 COMPLEX IN THE ABSENCE OF FIBRIN

The activity of tissue plasminogen activator-plasminogen activator inhibitor-1 (t-PA-PAI-1) complex to convert plasminogen to plasmin was examined by using fibrin autography and casein zymography where plasminogen was added or removed for casein layer. Fibrin autography was more sensitive to the activity of t-PA even in the complex with PAI-1, but casein zymography was more sensitive to plasmin. The inhibitory activity of PAI-1 towards t-PA diminished when plasma was clotted, thus in the presence of fibrin. These results indicate that t-PA-PAI-1 complex has a catalytic activity even in the absence of fibrin, but the activity is enhanced in its presence.