Fibrinogen (Factor I) (FI)

Fibrinogen is a large, soluble, hexameric glycoprotein synthesized by the liver that serves as the essential precursor to fibrin in the blood coagulation cascade (UniProt P02671, P02675, P02679). It consists of three pairs of polypeptide chains (alpha, beta, and gamma) that are cleaved by the enzyme thrombin during vascular injury to form fibrin monomers, which then polymerize into an insoluble mesh to stabilize blood clots (StatPearls NBK531483). Beyond its structural role in hemostasis, fibrinogen and its degradation products modulate inflammation, wound healing, and angiogenesis by interacting with various cell surface receptors like integrins (PubMed 18495336). Pathologically, the formation of stable fibrin clots can lead to life-threatening arterial or venous thrombosis, contributing to myocardial infarction and stroke. Therapeutic strategies include the use of thrombolytic drugs to dissolve existing fibrin clots and fibrinogen replacement therapy to manage bleeding in patients with quantitative or qualitative fibrinogen deficiencies (DrugBank DB09100). Monitoring fibrinogen levels and its cross-linked degradation product, D-dimer, is a standard clinical practice for diagnosing and managing thrombotic disorders.

Other names

FibrinCoagulation factor IFGA/FGB/FGG complexFibrin clotSoluble fibrinogen

Thrombolytic agents (plasminogen activators) bind to fibrin within a thrombus and convert entrapped plasminogen to plasmin, which enzymatically degrades the fibrin mesh (fibrinolysis). Fibrinogen replacement therapy restores plasma levels to facilitate clot formation in deficiency states, while defibrinogenating agents like ancrod deplete circulating fibrinogen to prevent new clot formation.