Coagulation factor XIII A2B2 heterotetramer (FXIII-A2B2)

Coagulation factor XIII A2B2 heterotetramer is the plasma-circulating form of the final enzyme in the blood coagulation cascade, acting as a pro-transglutaminase zymogen [1, 4]. It consists of two catalytic A subunits (FXIII-A) and two protective carrier B subunits (FXIII-B) [1, 8]. Upon activation by thrombin and calcium, the B subunits dissociate, allowing the A subunits to form the active transglutaminase, Factor XIIIa [7, 14]. The primary biological function of Factor XIIIa is to covalently cross-link fibrin polymers and attach anti-fibrinolytic proteins like alpha2-antiplasmin to the fibrin network, which provides essential mechanical strength and biochemical stability to the blood clot [13, 14]. Deficiency in this complex, whether congenital due to genetic mutations or acquired through consumption or autoantibodies, leads to severe bleeding disorders, impaired wound healing, and recurrent pregnancy loss [12, 13]. Therapeutic management typically involves replacement therapy with plasma-derived or recombinant Factor XIII concentrates to restore hemostatic function [8, 12]. Additionally, Factor XIII is being investigated as a target for novel antithrombotic agents, where inhibition of its cross-linking activity could produce clots that are more susceptible to fibrinolysis [16].

Other names

Plasma Factor XIIIFibrin-stabilizing factorLaki-Lorand factorFXIII-A2B2 complexPro-transglutaminaseCoagulation factor XIII, A1 polypeptideCoagulation factor XIII, B polypeptide

Replacement therapy restores the transglutaminase activity of the Factor XIII complex, enabling the covalent cross-linking of fibrin chains and the attachment of alpha2-antiplasmin to the fibrin network, which stabilizes the blood clot and protects it from premature fibrinolysis [1, 8, 13]. Experimental inhibitors target the active site of the activated A-subunit (FXIIIa) to prevent these cross-linking events, thereby reducing clot stability and enhancing susceptibility to lysis in thrombotic conditions [16].