factor Xa Va:Xa complex (prothrombinase) factor Va factor Va + factor Xa -> Va:Xa complex (prothrombinase) Authored: D'Eustachio, P, 2004-08-24 14:00:00 Factors Va and Xa associate on a membrane surface to form a complex in which the activity of factor Xa on prothrombin is greatly increased (Mann et al. 1988). The presence of negatively charged phospholipid in the membrane greatly facilitates this process, a feature that may contribute to its localization, as such phospholipids are normally on the cytosolic face of the plasma membrane (Devaux 1992), but could be exposed to the extracellular space following platelet activation or mechanical injury to endothelial cells. Pubmed1525472 Pubmed3052293 Reactome Database ID Release 43140686 Reactome, http://www.reactome.org ReactomeREACT_675