[Lethal in vivo and cytotoxic in vitro properties of a basic phospholipase A2 modified with para-bromophenacyl bromide].

Nigexine is a basic phospholipase A2 isolated from the venom of Naja nigricollis (Institut Pasteur). Previous works have shown that nigexine is (i) cytotoxic in vitro toward epithelial cells of FL strain and, (ii) toxic to mice (LD50 = 29 nmoles/kg). We have investigated the properties of nigexine treated with p-bromophenacyl bromide, a reagent which specifically destroys the enzymatic activity of phospholipases A2. We report that pure derivatized nigexine has no lethal detectable activity to mice whereas it still possesses a residual 20% cytotoxic activity, as compared with the parental compound.