Snake venom is a highly complex cocktail of proteins, peptides, non protein toxins, carbohydrates, lipids, amines and other molecules. The chemical composition of venom varies at all taxonomic levels. Further, composition can vary considerably between snakes in different geographical locations and individuals within those populations. The composition is also subject to change based on diet, age, season and environment. The widely differing manifestations of snake bite could be attributed to complexity of venom to some extent.
The snake venom mainly contains proteins (>90%, dry weight). There are more than hundred different proteins in each venom; with elapid and viperid venoms constituting 25-70% and 80-90% of enzymes respectively. Some non-enzymatic polypeptide toxins and non-toxic proteins are also present.
The snake venoms are mainly characterized as neurotoxic and hemotoxic. The neurotoxic venoms act at molecular level, by disrupting the neuromuscular junctions, limiting muscle activity while hemotoxic venoms cause tissue destruction in body systems besides their effect on circulatory system.
The venom enzymes include hydrolases, hyaluronidase, kininogenase. Other enzymes include phosphomono-and diesterases, 5’-nucleotidase, DNAase, NAD-nucleosidase, l-amino acid oxidase, phospholipase A2(PLA2), peptidases and zinc metalloproteinase hemorrhagins. Blood clotting may be stimulated by serine proteases and other pro-coagulant enzymes present in some Elapid and Viperid venoms. Certain venoms contain toxins (Russell’s viper) that activate factors V, X, IX and XIII, fibrinolysis, protein C, platelet aggregation,anticoagulation and hemorrhage.
Widespread damage to mitochondria, red blood cells, leucocytes, platelets, peripheral nerve endings, skeletal muscle, vascular endothelium, and other membranes is caused due to phospholipase A2, the most widespread enzyme present in the venom. Hyaluronidase aids in venom dissemination from the bite site through tissues.