NEUTRALIZATION OF THE CYTOLYTIC AND MYOTOXIC ACTIVITIES OF PHOSPHOLIPASES A(2) FROM BOTHROPS-ASPER SNAKE-VENOM BY GLYCOSAMINOGLYCANS OF THEHEPARIN HEPARAN SULFATE FAMILY/

Basic phospholipases A(2) from the venom of Bothrops asper exhibit ske letal muscle damaging activity in vivo, and cytolytic activity to a va riety of cell types in culture. Glycosaminoglycans of the heparin/hepa ran sulfate family were found to be potent blockers of the cytolytic a ction in vitro, and, as well, to be able to neutralize the muscle dama ging activity of purified myotoxins and crude venom in vivo. However, the neutralizing effect of heparins was more potent in vitro than in v ivo. The cytolytic activity of myotoxin II (a lysine-49 phospholipase A(2) isoform) and its inhibition by heparin was characterized. The neu tralizing effect of heparin did not depend on its anticoagulant activi ty, since both standard heparin and heparin with low affinity for anti thrombin (LA-heparin) had a similar efficiency. Heparan sulfate and lo w molecular mass heparin (5 kDa) also neutralized myotoxin II. In cont rast, different heparin-derived disaccharides were unable to block cyt olysis, implying a requirement for a longer carbohydrate chain structu re for the interaction with the protein. By affinity chromatogaphy and gel diffusion, it was demonstrated that heparins form a complex with all isoforms of basic venom myotoxins, held at least in part by electr ostatic interactions. The phospholipase A(2) activity of myotoxin III, a related aspartate-49 isoform from the same venom, was unaffected by heparins, despite the fact that its myotoxic activity was inhibited, indicating a dissociation of the two actions.