Isolation and characterization of “Reprotoxin”, a novel protein complex from Daboia russelii snake venom

In snake venoms, non-covalent protein–protein interaction leads to protein complexes with synergistic and, at times, distinct pharmacological activities. Here we describe a new protein complex containing phospholipaseA2 (PLA2), protease, and a trypsin inhibitor. It is isolated from the venom of Daboia russelii by gel permeation chromatography, on a Sephadex G-75 column. This 44.6 kDa complex exhibits only phospholipase A2 activity. In the presence of 8 M urea it is well resolved into protease (29.1 kDa), PLA2 (13 kDa), and trypsin inhibitor (6.5 kDa) peaks. The complex showed an LD50 of 5.06 mg/kg body weight in mice. It inhibited the frequency of spontaneous release of neurotransmitter in hippocampal neurons. It also caused peritoneal bleeding, and edema in the mouse foot pads. Interestingly, the complex caused degeneration of both the germ cells and the mouse Leydig cells of mouse testis. A significant reduction in both the diameter of the seminiferous tubules and height of the seminiferous epithelia were observed following intraperitoneal injection of the sub-lethal dose (3 mg/kg body weight). This effect of the toxin is supported by the increase in the activities of acid and alkaline phosphatases and the nitric oxide content in the testes, and a decrease in the ATPase activity. Because of its potent organ atrophic effects on the reproductive organs, the toxin is named “Reprotoxin”. This is the first report demonstrating toxicity to the reproductive system by a toxin isolated from snake venom.