Fibrinolytic serine protease

Serine proteases involved in fibrinolysis are a group of enzymes responsible for the breakdown of fibrin clots, a process essential for maintaining vascular patency and preventing thrombosis. The primary members of this group include plasmin, which directly degrades fibrin, and its activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA). These enzymes are tightly regulated by endogenous inhibitors such as plasminogen activator inhibitor-1 (PAI-1) and alpha-2-antiplasmin to prevent excessive bleeding or unwanted clot dissolution. In clinical practice, recombinant forms of tPA (e.g., alteplase) are used as thrombolytic agents to treat acute myocardial infarction, ischemic stroke, and pulmonary embolism by accelerating the conversion of plasminogen to plasmin. Conversely, inhibitors of these proteases, such as tranexamic acid, are employed as antifibrinolytics to reduce blood loss in surgery or trauma. Dysregulation of this system is implicated in various cardiovascular diseases and can also play a role in cancer progression and tissue remodeling.

Other names

Fibrinolytic enzymesPlasminogen activatorsPlasminTissue-type plasminogen activator (tPA)Urokinase-type plasminogen activator (uPA)Fibrinolytic serine proteases

Thrombolytic agents (plasminogen activators) catalyze the conversion of the zymogen plasminogen into the active serine protease plasmin, which proteolytically cleaves fibrin into soluble fragments to dissolve clots. Antifibrinolytic agents either competitively inhibit the lysine-binding sites of plasminogen and plasmin, preventing their association with fibrin, or directly inhibit the catalytic activity of the serine proteases to stabilize clots and reduce bleeding.