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

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Abstract
Two phospholipases A, CM‐II and CM‐III, were purified from the Siamese cobra (Naja raja 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 halfcystine 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.