Coagulation factor Xa-antithrombin III complex (FXa-ATIII)

The Coagulation factor Xa-antithrombin III complex is a molecular assembly formed during the regulation of the blood coagulation cascade (UniProt P00742, P01008). Factor Xa is a key serine protease that catalyzes the conversion of prothrombin to thrombin, the final enzyme required for fibrin clot formation (PubMed: 15606376). Antithrombin III serves as the primary physiological inhibitor of Factor Xa, belonging to the serine protease inhibitor (serpin) superfamily (StatPearls: Antithrombin III Deficiency). The formation of this complex effectively neutralizes the enzymatic activity of Factor Xa, thereby halting the progression of clot formation (NIH: Coagulation Cascade). This interaction is the primary target for indirect anticoagulant drugs, such as heparin and its derivatives, which bind to antithrombin III to enhance its inhibitory rate by several thousand-fold (PubChem: Heparin). Clinically, this mechanism is exploited to treat and prevent various thrombotic conditions, including deep vein thrombosis, pulmonary embolism, and myocardial infarction (Mayo Clinic: Anticoagulants). Understanding the structural and functional dynamics of this complex is essential for developing safer anticoagulants with reduced bleeding risks (Journal of Biological Chemistry). Measurement of the complex or the activity of its components is frequently used in clinical settings to monitor patient response to therapy (LabCorp: Anti-Xa Assay).

Other names

Factor Xa-antithrombin complexFXa-AT complexAntithrombin-Factor Xa complexFXa-ATIII complex

Indirect inhibition of Factor Xa through the allosteric potentiation of Antithrombin III, which forms a stable 1:1 stoichiometric complex with the enzyme to neutralize its procoagulant activity.