Snake venom prothrombin activators similar to blood coagulation factor Xa.

Activation of prothrombin to mature thrombin in vivo occurs by the proteolytic action of the prothrombinase complex consisting of serine proteinase factor Xa, and cofactors that include factor Va, Ca(2+) ions and phospholipids. Several exogenous prothrombin activators are found in snake venom. Among these, Group C prothrombin activators resemble the factor Xa-factor Va complex, while Group D activators are structurally and functionally similar to factor Xa. This review provides a detailed description of current knowledge on Group D prothrombin activators and highlights the importance of studying this family of proteins in enhancing our understanding of structure-function relationships in the mammalian prothrombinase complex.