Thrombin-like snake venom serine protease. Cleaves Arg-Gly bonds in fibrinogen alpha chains (FGA). Selective cleavage of Arg-|-Xaa bond in fibrinogen, to form fibrin, and release fibrinopeptide A. The specificity of further degradation of fibrinogen varies with species origin of the enzyme. Monomer. Expressed by the venom gland. Is used for the investigation of the last phase of blood coagulation. Due to its heparin insensitivity it can detect fibrinogen polymerization disorders even in the presence of heparin. Available under the name Defibrase (Pentapharm) for the treatment of thrombotic diseases. Does not cleave beta-chains of fibrinogen (FGB). Belongs to the peptidase S1 family. Snake venom subfamily.