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. 2010 May;8(5):865-7.
doi: 10.1111/j.1538-7836.2010.03832.x. Epub 2010 Mar 3.

Platelet polyphosphate: an endogenous activator of coagulation factor XII

N Mackman  1 , A Gruber
Affiliations

Platelet polyphosphate: an endogenous activator of coagulation factor XII

N Mackman et al. J Thromb Haemost. 2010 May.
No abstract available

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Figures

Fig. 1
Fig. 1
Different ways to activate the clotting cascade. The extrinsic pathway consists of TF and FVII/VIIa (orange) and is activated by either vascular injury or by TF expression within the vasculature. The intrinsic pathway consists of FXII, FXI, FIX and FVIII (turquoise) and is activated at various levels by polyP, thrombin and TF-FVIIa. The common pathway consists of FV and FX, and prothrombin (II) (pink). Finally, fibrin is converted into cross-linked fibrin by FXIIIa. Platelets (Plt) contribute to the clotting cascade by releasing polyP, which activates FXII, and by providing a surface for the assembly of the different complexes, such as the intrinsic tenase complex (FVIIIa–FIXa) and the prothrombinase complex (FVa–FXa). The clotting cascade can be activated by the generation of small amounts of thrombin via either the extrinsic pathway (TF-FVIIa to FXa or TF-FVIIa to FIXa to FXa), or via the intrinsic pathway (FXIIa to FXIa to FIXa to FXa). The propagation phase involves the generation of large amounts of thrombin by the prothrombinase complex (FVa–FXa). PolyP also modulates coagulation by accelerating the activation of FV and by enhancing fibrin polymerization.
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