Antithrombin-III (ATIII) – Factor Xa (FXa) complex (ATIII-FXa)

The Antithrombin-III – Factor Xa complex is a critical molecular assembly in the regulation of the human coagulation cascade [Source: UniProt P01008]. Antithrombin-III (ATIII), a member of the serine protease inhibitor (serpin) family, acts as a natural anticoagulant by forming a stable, inactive complex with the serine protease Factor Xa (FXa), thereby preventing the conversion of prothrombin to thrombin [Source: StatPearls, Heparin]. This inhibitory interaction is naturally slow but is accelerated by several orders of magnitude in the presence of heparin or synthetic pentasaccharides like fondaparinux [Source: PubChem, Fondaparinux]. These drugs bind to a specific pentasaccharide sequence on ATIII, inducing an allosteric conformational change that exposes the reactive center loop for rapid interaction with FXa [Source: NIH, Anticoagulants]. Dysregulation or deficiency of this system is strongly linked to thrombotic disorders, including deep vein thrombosis and pulmonary embolism [Source: PubMed, PMID: 11375370]. Consequently, the ATIII-FXa interface is a primary therapeutic target for anticoagulant therapy in patients at risk of thromboembolic events. Monitoring of this target's activity is typically performed using the Anti-Factor Xa assay to ensure therapeutic efficacy and minimize bleeding risks [Source: Mayo Clinic Laboratories].

Other names

Antithrombin III – Factor Xa interfaceATIII-FXa interactionSerpin C1-Factor Xa complexAntithrombin-Factor Xa complex

Drugs bind to Antithrombin-III, inducing a conformational change that accelerates its natural inhibitory activity against Factor Xa by several thousand-fold [Source: StatPearls].