Snake venom zinc metalloproteinase that inhibits ristocin-induced platelet aggregation by abolishing the binding of von Willebrand factor (vWF) to platelet glycoprotein Ib alpha (GPIBA) through the cleavage of both GP1BA and vWF. Also has fibrinogenolytic activities by degrading the alpha- (FGA) and beta-chain (FGB) of fibrinogen. In vivo, induces a slight hemorrhage when applied to chick chorioallantoic membrane and has potent antithrombic effect. Binds 1 zinc ion per subunit. Monomer. Expressed by the venom gland. This protein autoproteolytically degrades to 10 kDa and 14 kDa fragments in the presence of SDS. Interestingly, the two fragments, as well as reduced crotalin are able to bind vWF, indicating that the binding activity does not require a specific protein conformation. Does not induce thrombocytopenia after injection into mice. Belongs to the venom metalloproteinase (M12B) family. P-I subfamily. This fragmental protein is 100% identical to atrolysin-B (AC Q90391) and may be the same protein.