Action on phosphatidylcholine of the toxic phospholipase A 2 from the venom of Bulgarian viper ( Vipera ammodytes ammodytes)

Abstract

The action of the neurotoxic complex and its components from the venom of the Bulgarian viper ( Vipera ammodytes ammodytes) on phosphatidylcholine was studied. The nontoxic acidic component partially inhibited the phospholipase A 2 activity of the strongly toxic basic component. The basic component, separated from the acidic, was unstable and in the course of 12–14 days lost its enzymatic activity. The Michaelis constant, K m = 1 × 10 −3M was the same for the free phospholipase A 2 and the neurotoxic complex. Temperature optimum was 23–26°C and pH optimum was 9.9–10. A concentration of 1–3 × 10 −3 M CaCl 2 was required for maximum enzyme activity. The influence of divalent cations on the initial velocity of the enzyme hydrolysis was studied. Although composed of a basic toxic phospholipase A 2 and a nontoxic acidic component the neurotoxic complex exhibited an insignificant enzyme activity.