Snake prothrombin activator that attacks the hemostatic system of prey. This protein is functionally similar to blood coagulation factor Xa. Selective cleavage of Arg-|-Thr and then Arg-|-Ile bonds in prothrombin to form thrombin. Heterodimer of a light chain and a heavy chain; disulfide-linked. Expressed by the venom gland. Gamma-carboxyglutamate residues are formed by vitamin K dependent carboxylation. These residues are essential for the binding of calcium. Is classified in the group D of snake venom prothrombin activators, since it requires the mammalian factor Va for maximal activity for the cleavage of prothrombin. The venom of this species does not contains its own coagulation factor V-like. In contrast to blood coagulation factors that circulate as inactive zymogen in plasma, venom prothrombin activators are always found in the active form in the venom. Belongs to the peptidase S1 family. Snake venom subfamily.