Factor Va (Last Updated - 2/27/2005)

-makes up a step of the common pathway
-formed via activation of Factor V --> this reaction is catalyzed by Factor IIa (thrombin)
-Factor Va (along with calcium (Factor IV) & phospholipids) in turn catalyzes the activation of Factor II (Prothrombin) to Factor IIa (Thrombin) --> positive feedback loop

-click here to view an image of the clotting cascade

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References:

Goodman & Gilman's: The Pharmacologic Basis Of Therapeutics - 10th Edition - 2001. Chapter 55.