Plasmin (and related trypsin-like serine proteases) (PLG)

Plasmin is the primary serine protease responsible for fibrinolysis, the physiological process of dissolving blood clots. It is produced from its inactive precursor, plasminogen, through cleavage by activators such as tissue plasminogen activator (tPA) or urokinase-type plasminogen activator (uPA) (UniProt P00747; StatPearls: Physiology, Fibrinolysis). Once activated, plasmin degrades fibrin into soluble degradation products, thereby maintaining vascular patency. Beyond its role in hemostasis, plasmin participates in tissue remodeling, wound healing, and the activation of various matrix metalloproteinases (PubMed: Plasminogen system in inflammation and tissue remodeling). In pathology, dysregulation of the plasmin system contributes to thrombotic disorders, excessive bleeding, and tumor metastasis (PubMed: The role of plasminogen in cancer). Pharmacological modulation of this system is a cornerstone of emergency medicine, where thrombolytic agents are used to treat acute stroke and myocardial infarction, while antifibrinolytic drugs like tranexamic acid are employed to control surgical and traumatic bleeding (StatPearls: Thrombolytic Therapy; StatPearls: Tranexamic Acid).

Other names

FibrinolysinPlasminogenSerine protease S1 familyTrypsin-like serine proteases

Plasminogen activators catalyze the conversion of inactive plasminogen to active plasmin, which then enzymatically degrades fibrin polymers into soluble fragments. Conversely, antifibrinolytic agents bind to the lysine-binding sites of plasminogen and plasmin, inhibiting their interaction with fibrin and preventing clot dissolution. Direct inhibitors like aprotinin bind to the active site of the enzyme to block its proteolytic activity.