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How does plasmin dissolve fibrin clots during fibrinolysis?
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bleeding and blood clotting
Red blood cells (erythrocytes) trapped in a mesh of fibrin threads. Fibrin, a tough, insoluble protein formed after injury to the blood vessels, is an essential component of blood clots.
Plasmin is the active enzyme responsible for fibrinolysis, the process by which the body dissolves fibrin clots at injury sites or within blood vessels.12
The mechanism functions as follows:
- Activation: Plasmin is derived from an inert precursor protein called plasminogen. This conversion is triggered by activating factors, such as tissue plasminogen activator (t-PA), which are released from endothelial cells.12
- Dissolution: Once activated, plasmin acts as a protease that catalyzes the degradation of fibrin threads. By breaking down these fibrous chains, plasmin effectively removes the structural component of the blood clot.123
- Regulation: In the circulating blood, plasmin is typically kept in check by a specific circulating inhibitor to prevent systemic breakdown of coagulation factors. When the fibrinolytic system is excessively activated, however, plasmin may also degrade fibrinogen, a process known as fibrinogenolysis, which can lead to hemorrhage.1