The Amino-Acid Sequence and Carbohydrate Content of Phospholipase A2 from Bee Venom

The complete amino acid sequence of phospholipase A2 from the venom of the common European honey-bee (Apis mellifica) has been determined. The sequence of amino acid residues at the N-terminus was obtained by direct application of the Edman degradation technique and that at the C-terminus by digestion with carboxypeptidases A and B. Digestion of the reduced and carboxymethylated enzyme with trypsin yielded a completely soluble peptide mixture, all the components of which were isolated and their structures determined. Overlaps of the tryptic peptides were deduced from the structures of peptides isolated after digestion of the reduced and carboxymethylated enzyme with chymotrypsin and of the reduced and aminoethylated enzyme with a protease specific for cleavage at lysine residues. Two remaining ambiguities were resolved by peptides obtained from a digest of the reduced, carboxymethylated and maleylated enzyme with trypsin. The phospholipase A2 consists of a single chain of 128 amino acid residues and contains attached carbohydrate residues. The composition and point of attachment of the carbohydrate moiety have been established.