Presynaptic and musculotropic effects of a basic phospholipase A2 from the Formosan habu (Trimeresurus mucrosquamatus) venom.

A basic phospholipase A2 purified from the venom of a crotalid snake (Trimeresurus mucrosquamatus) was applied to chick and mouse neuromuscular preparations. The enzyme at lower concentrations (1-3 micrograms/ml) blocks neuromuscular transmission at a presynaptic site, while at higher concentrations (10-30 micrograms/ml) it causes contracture and depolarization of the muscle as well. It is concluded that the mode of action of the enzyme on vertebrate nerve-muscle transmission is similar to that of notexin and ceruleotoxin from elapid snake venoms.