Isolation and preliminary characterisation of two toxic phospholipases A2 from the venom of the Malayan cobra (Naja naja sputatrix).

Two toxic phospholipases A have been isolated from the venom of the Malayan cobra (Naja naja sputatrix). The phospholipases A were purified by successive ion-exchange chromatography on SP-Sephadex C-25, Sephadex G-75 gel filtration chromatography and successive Bio-Rex 70 ion-exchange chromatography. The purified toxic phospholipases A were homogeneous electrophoretically. They were designated as sputatrix phospholipase A-I and sputatrix phospholipase A-II. Positional specificity studies showed that they belong to the A2-type phospholipase A. The medium lethal dose 50% (LD50) values of the two phospholipases A are 0.27 and 0.28 microgram/g, respectively, by intravenous injection and 1.05 and 1.00 microgram/g, respectively, by intraperitoneal injection. The molecular weights of the two enzymes are 14000 as determined by gel-filtration chromatography and SDS-polyacrylamide gel electrophoresis. Amino acid composition of sputatrix phospholipase A-I differs from sputatrix phospholipase A-II only by having one extra amino acid: a glutamic acid. Amino acid compositions of the two enzymes are also similar to those of other cobra venom phospholipases A.