Hemolytic and anticoagulant study of the neurotoxin vipoxin and its components-basic phospholipase A sub(2) and an acidic inhibitor

In the present study, we demonstrate for the first time that the potent neurotoxin vipoxin from the venom of Vipera ammodytes meridionalis exhibits hemolytic and anticoagulant properties. By investigating the effects of phospholipids and calcium ions on hemolysis, we established that the phospholipase A sub(2) (PLA sub(2)) enzyme activity is responsible for the hemolytic properties. This was confirmed by chemical modification of the PLA sub(2) active-site histidine residue with p-bromophenacylbromide. Applying different clotting assays, we show that the PLA sub(2) is a weakly anticoagulant enzyme, which affects intrinsic tenase complex by the hydrolysis of procoagulant phospholipids, rather than by nonenzymatic mechanisms (binding to specific coagulation factors). The whole complex-vipoxin-does not affect the coagulation system.