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One of the more dramatic consequences of envenomation by crotalid and viperid snakes is the occurrence of hemorrage. In cases where the envenomation is less severe, the hemorrhagic is generally observed to be localized at the site of the bite. However, hemorrhage can be found disseminated through a substantial area of the involved extremity. In cases where the envenomation is severe, bleeding in organs such as heart, lungs, kidneys and brain may also occur. From the biochemical investigations on these toxins over the past 30 years, the nature of the venom toxins and their mechanism of activity are now becoming clear. Virtually all of the hemorrhagic toxins isolated and characterized thus far have been determined to be metalloproteinases. In this review we discuss the history of the isolation and characterization of these toxins in an attempt to clarify some of the confusion surrounding these toxins and their biochemical activities. We also survey the data available on the natural and synthetic inh...

Rattlesnake envenomation gives rise to many dramatic symptoms in the victim. Included among these are hypotension and hemorrhage. In this paper we present the results of our investigations on several proteases isolated from the venom of Crotalus atror (Western diamondback rattlesnake) which are probably involved in crotalid venom caused hypotension and hemorrhage.We have isolated two proteases (EI and EII) from C. atrox venom which have molecular weights of 27,500 and 29,200 and isoelectric points of 4.7 and 4.3 respectively. Both enzymes did not demonstrate any proteolytic activity on the oxidized chains of insulin and glucagon. Neither enzyme had any plasmin or fibrinolytic activity but both could release bradykinin from a kininogen analog. This proteolytic activity was inhibited by aprotinin and PMSF (phenylmethylsulfonyl fluoride) but not by EDTA (ethylenediamine tetraacetate). The enzymes were demonstrated to be structurally similar but not identical from spectroscopic, peptide mapping, and s...