Amino acid sequence of phospholipase A2 from horse pancreas.

The complete amino acid sequence of phosphlipase A2 (EC 3.1.1.4) from horse pancreas was determined. The protein controls of a single polypeptide chain of 125 amino acids and has a molecular weight of 13,927. The chain is crosslinked by seven disulfide bridges. The sequence was determined by automated Edman degradation of the intact protein and several of the large peptide fragments. Smaller peptides were analyzed by manual Edman degradation. Fragmentation of the peptide chain was accomplished by enzymatic digestion with trypsin, chymotrypsin, and thermolysin. The final overlap was found by digestion of the polypeptide with a staphylococcal protease specific for glutamoyl bonds. Phospholipase A2 from horse pancreas shows homology to snake venom phospholipases A2 and to the enzyme from porcine pancreas, provided that the published amino acid sequence of the porcine phospholipase A2 is revised to some extent.