Fibrinogen and Plasminogen (FG/PLG)

Fibrinogen and plasminogen are central proteins in the regulation of blood coagulation and clot dissolution. Fibrinogen (Factor I) is a hexameric glycoprotein synthesized in the liver that is cleaved by thrombin to form fibrin, the primary protein component of a blood clot (StatPearls, 2023). Plasminogen is a circulating zymogen that, when activated by tissue-type plasminogen activator (tPA) or urokinase, becomes plasmin, the serine protease responsible for degrading fibrin into soluble fragments (UniProt P00747). This system is a major therapeutic target; thrombolytic drugs like alteplase mimic endogenous activators to convert plasminogen to plasmin for the treatment of acute ischemic stroke and myocardial infarction (PubMed, PMC3444856). Conversely, antifibrinolytic agents such as tranexamic acid inhibit plasminogen activation to reduce blood loss in surgery or trauma (NIH, 2022). Dysregulation of this balance leads to pathological states including thrombosis, disseminated intravascular coagulation, and various bleeding disorders.

Other names

Factor IFGAFGBFGGPLGFibrinogen complexPlasminogen zymogenFibrinolytic system

Thrombolytic drugs function as plasminogen activators, converting the zymogen plasminogen into the active protease plasmin, which then cleaves the fibrin meshwork of a thrombus. Antifibrinolytic drugs competitively inhibit the activation of plasminogen by binding to its lysine-binding sites, thereby preventing its interaction with fibrin and subsequent conversion to plasmin.