Effects of chlorpromazine on the enzymatic and toxic properties of the most basic phospholipase A2 from Vipera russelli snake venom.

The effect of chlorpromazine on various biological activities of phospholipase A2 VRV-PL-VIIIa from Vipera russelli snake venom was investigated. The drug inhibited the in vitro phospholipase A2 activity of the enzyme by 55%. The ID50 was found to be 1.15 microM. Increasing substrate concentration relieved the inhibition of phospholipase A2 activity by the drug indicating probable interaction with the substrate. The drug totally quenched the fluorescence intensity of the enzyme. Chlorpromazine increased the LD50 of the enzyme by 1.6 fold. The drug also inhibited hemolytic and anticoagulant potencies but failed to inhibit edema inducing activity and myotoxicity of the enzyme.