Purification, Some Properties and Amino‐Acid Sequences of Two Phospholipases A (CM‐II and CM‐III) from Naja naja kaouthia Venom

Two phospholipases A, CM-II and CM-III, were purified from the Siamese cobra (Naja naja kaouthia) venom, from Thailand, by gel filtration on Sephadex G-50 followed by ion-exchange chromatography on CM-cellulose. They each comprise 119 amino acid residues including 14 half-cystine residues. The complete primary structures of the two phospholipases A have been elucidated and their sequences are 96% identical. The sequences, the invariant amino acid residues and the sequences around the active center (histidine-48) of CM-II and CM-III resemble those from other snake venoms and also from mammalian pancreas. Further, the cysteine residues are in similar locations to those in phospholipase A of known structure so they are presumed to link similarly. The two phospholipases A from N.n. kaouthia venom each contain a single histidine residue which is located at the active center (histidine-48). The toxicities of the two enzymes differ among themselves, but are comparable to those encountered for phospholipases A from African cobra venoms.