Factor Xa activation of factor V is of paramount importance in initiating the coagulation system: lessons from a tick salivary protein.

ABSTRACT:

Background

Generation of active procoagulant cofactor factor Va (FVa) and its subsequent association with the enzyme activated factor X (FXa) to form the prothrombinase complex is a pivotal initial event in blood coagulation and has been the subject of investigative effort, speculation, and controversy. The current paradigm assumes that FV activation is initiated by limited proteolysis by traces of (meizo) thrombin.

Methods and results

Recombinant tick salivary protein TIX-5 was produced and anticoagulant properties were studied with the use of plasma, whole blood, and purified systems. Here, we report that TIX-5 specifically inhibits FXa-mediated FV activation involving the B domain of FV and show that FXa activation of FV is pivotal for plasma and blood clotting. According

SUBMITTER: Schuijt TJ 

PROVIDER: S-EPMC3826089 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature