Biochemical and pharmacological properties of cardiotoxins isolated from cobra venom.

It has been established that cardiotoxins isolated from Elapidae snakes tend to be contaminated with phospholipase. After a thorough comparison of the methods available for the separation of these two components, both hydrophobic and immunoaffinity chromatography have been found to be convenient and effective methods. With cardiotoxins isolated from Naja naja siamensis we observed that as the contaminating phospholipase was removed, the cardiotoxins were converted from relatively powerful haemolytic agents to essentially nonlytic agents. In contrast, removal of the contaminating phospholipase did not abolish the ability of the cardiotoxins to contract smooth muscle. Homologous toxins isolated from Naja melanoleuca and Haematchatus haematchates have been isolated with powerful lytic activity and weak or low cardiotoxicity. This data is interpreted in the light of the homologous group of cardiotoxins possessing two different properties (1) cardiotoxicity and (2) lytic activity; some molecules in the group possess both properties and other possess only one or the other. Structure activity relationships are presented in support of this concept.