Which agent directly activates plasminogen by binding to it in fibrinolysis?

Which agent directly activates plasminogen by binding to it in fibrinolysis?

• A. Thrombin
• B. Plasmin
• C. Streptokinase
• D. Tissue plasminogen activator

Answer: (D)

In fibrinolysis, plasminogen is activated to plasmin by proteases that bind plasminogen and catalyze its conversion. Tissue plasminogen activator directly binds plasminogen and cleaves it to form plasmin, especially when plasminogen is associated with fibrin in a clot. This targeted activation localizes fibrinolysis to the thrombus, helping to dissolve the clot without widespread degradation of fibrin elsewhere. Thrombin is a coagulation factor that promotes clot formation, not plasminogen activation. Plasmin is the active enzyme that degrades fibrin, not the activator. Streptokinase can activate plasminogen, but it does so by forming a complex with plasminogen to become an activator, rather than directly binding plasminogen itself to activate it. Thus, the agent that directly activates plasminogen by binding to it is tissue plasminogen activator.

In fibrinolysis, plasminogen is activated to plasmin by proteases that bind plasminogen and catalyze its conversion. Tissue plasminogen activator directly binds plasminogen and cleaves it to form plasmin, especially when plasminogen is associated with fibrin in a clot. This targeted activation localizes fibrinolysis to the thrombus, helping to dissolve the clot without widespread degradation of fibrin elsewhere. Thrombin is a coagulation factor that promotes clot formation, not plasminogen activation. Plasmin is the active enzyme that degrades fibrin, not the activator. Streptokinase can activate plasminogen, but it does so by forming a complex with plasminogen to become an activator, rather than directly binding plasminogen itself to activate it. Thus, the agent that directly activates plasminogen by binding to it is tissue plasminogen activator.