Factor Va Cofactor Activity Is Dependent on the Interaction of Prothrombin with the Membrane Surface.

Abstract Activation of human prothrombin (Pro) occurs because of two sequential cleavages in prothrombin by membrane-bound factor Xa (fXa) (Arg271 followed by Arg320, prethrombin 2 pathway). However, the catalytic efficiency of membrane-bound fXa is poor in the absence of factor Va (fVa), and the overall reaction is incompatible with efficient thrombin formation required for the timely arrest of bleeding. Binding of fVa to fXa …