Fibrinogen is the main protein of blood coagulation system. It is a large protein and it consists of two identical subunits that contain three polypeptide chains: alpha, beta and gamma. All chains are connected with each other by a number of disulfide bonds. Fibrinopeptides A (1 to 16 amino acids) and B (1 to 17 amino acids) are released by thrombin from the N terminal parts of alpha and beta chains, respectively. In this way fibrinogen is converted into fibrin, which by means of polymerization forms a fibrin clot. Fibrinogen clotting underlies pathogenesis of MI, thromboembolism and thromboses of arteries and veins, since fibrin is the main substrate for thrombus formation. Fibrinogen activation is also involved in pathogenesis of inflammation, tumor growth and many other diseases.