Factor IXa-factor VIIIa intrinsic tenase complex (FIXa-FVIIIa) (FIXa-FVIIIa)

The Factor IXa-factor VIIIa intrinsic tenase complex is a multi-component enzymatic assembly essential for the propagation phase of the blood coagulation cascade. It consists of the activated serine protease Factor IXa and its non-enzymatic cofactor Factor VIIIa, which assemble on negatively charged phospholipid surfaces in the presence of calcium ions [StatPearls, PMID: 30020604]. The primary function of this complex is to catalyze the conversion of zymogen Factor X into the active protease Factor Xa, a step that is several orders of magnitude more efficient than activation by Factor IXa alone [PubMed, PMID: 11566328]. Dysregulation or deficiency of the components of this complex results in significant clinical pathologies; a lack of Factor VIII leads to Hemophilia A, while a lack of Factor IX causes Hemophilia B [UniProt, P00451; P00740]. Therapeutic interventions often focus on replacing the missing factors or using bypass agents and mimetic antibodies, such as emicizumab, which bridges Factor IXa and Factor X to restore the complex's function in the absence of Factor VIII [NEJM, PMID: 28854339]. Monitoring the activity of this complex is vital for managing bleeding disorders and assessing the risk of thrombotic events.

Other names

FIXa-FVIIIa complexIntrinsic tenase complexFactor IXa-Factor VIIIa complexTenase complex

The complex catalyzes the proteolytic activation of Factor X to Factor Xa on phospholipid surfaces in the presence of calcium ions.