Gyroxin, a toxin from the venom of Crotalus durissus terrificus, is a thrombin-like enzyme.

We report a simple method for the isolation of gyroxin, a protein from the venom of the South American rattlesnake Crotalus durissus terrificus. The intravenous injection of gyroxin into mice produces temporary episodes characterized by opisthotonos and rotations around the long axis of the animal. We found gyroxin to be a glycoprotein with thrombin-like and esterase activities. Gyroxin loses its ability to produce the gyroxin syndrome, its thrombin-like activity and its esterase activity with heat, dithiothreitol, phenylmethylsulfonyl fluoride or diisopropylfluorophosphate. We also report that three other thrombin-like enzymes, crotalase from the eastern diamondback rattlesnake (Crotalus adamanteus), ancrod from the Malayan pit viper (Agkistrodon rhodostoma) and a thrombin-like enzyme from the Central American rattlesnake (Crotalus durissus durissus), produce the gyroxin syndrome in mice. These enzymes may work by releasing neuroactive peptides from endogenous precursors.