Definition: A thrombin-like enzyme from the venom of snakes of the viper/rattlesnake group. Species variants of the enzyme include ANCROD (Agkistrodon rhodostoma (Malayan pit viper)); BATROXOBIN from Bothrops atrox; and crotalase from Crotalus adamanteus (Eastern diamondback rattlesnake). EC 3.4.21.74.