Characterization of the platelet aggregation inducer and inhibitor from Echis carinatus snake venom

Echis carinatus venom was separated into twenty fractions by means of ultrafiltration and CM-Sephadex C-50 column chromatography. Fraction II possessed inhibitory activity on the aggregation of washed rabbit platelets and fraction XII possessed the procoagulant and platelet aggregation-inducing activity. Both were further purified by gel filtration on a Sephacryl S-200 column. The purified aggregation inducer was a glycoprotein with procoagulant activity 10-12-times that of the crude venom. It possessed proteinase and amidase but was devoid of esterase activity. The molecular weight was 16 000, and it contained 8.7% of neutral sugar. The isoelectric point was pH 7.6. The purified aggregation inhibitor was a single peptide chain with a molecular weight of 6800 and contained 22.1% of neutral sugar. The isoelectric point was pH 4.8. It was devoid of any enzymatic activity of the crude venom. The IC50 was about 10 micrograms/ml on the thrombin-induced platelet aggregation. The inhibitory activity was fully retained after the treatment of the venom aggregation inhibitor with neuraminidase, but was completely destroyed by sodium metaperiodate. Upon heat treatment at 90 degrees C, the venom aggregation inhibitor was heat stable at pH 5.5 for 4 h, but was completely destroyed after 2 h at pH 8.9 and retained about 50% of its inhibitory activity of the control at pH 7.2 for 4 h. The venom aggregation inhibitor decreased the elasticity of the whole blood clot, and this effect was related to its inhibitory action on platelet aggregation instead of blood coagulation.