factor IXa factor VIIIa:factor IXa factor VIIIa factor VIIIa + factor IXa -> factor VIIIa:factor IXa Authored: D'Eustachio, P, 2005-01-20 14:44:36 Edited: D'Eustachio, P, 0000-00-00 00:00:00 Pubmed8626656 Reactome Database ID Release 43158278 Reactome, http://www.reactome.org ReactomeREACT_112 The activated forms of factors VIII and IX associate on a cell surface to form a complex that very efficiently catalyzes the activation of factor X, the so-called "intrinsic tenase complex". In vitro, negatively charged phospholipids can provide an appropriate surface. In the body, the surface is provided by the plasma membranes of activated platelets (Gilbert and Arena 1996).