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. Author manuscript; available in PMC: 2011 Aug 9.
Published in final edited form as: Hamostaseologie. 2009 Jan;29(1):7–16.

Figure 2. Complex catalysts.

Figure 2

Three complexes are shown: the extrinsic fXase (Tf-fVIIa); the intrinsic fXase (fVIIIa-fIXa); and prothrombinase (fVa-fXa). The fXa generated by the fVIIa-Tf complex activates complex a small amount of thrombin which activates fV and fVIII leading to the presentation of the intrinsic fXase and prothrombinase complexes (panel A). The thick arrow representing fXa generation by the intrinsic fXase complex illustrates the ~50-fold more efficient fXa generation by this catalyst. The tissue factor pathway inhibitor, TFPI, interacts with the fVIIa-Tf-fXa product complex to block the Tf-initiated activation of both fIX and fX leaving the fIX-fVIIIa complex as the only viable catalyst for fX activation (panel B). Used with permission from the “Dynamics of Hemostasis” Haematologic Technologies, K.G. Mann, 2002.