The primary structure of porcine pancreatic elastase. The N-terminus and disulphide bridges.

1. The amino acid composition and N-terminal groups of purified elastase show that it is a single peptide chain of 234 residues. 2. The N-terminal sequence is Val-Val-Gly-Gly-Thr-Glu-. 3. The sequences around the four disulphide bridges were determined by using a ;diagonal' electrophoretic technique. 4. These four bridges are homologous with the four common to bovine trypsin and chymotrypsin. 5. Out of 83 residues of the elastase sequence so far determined, 43 are homologous with similar regions of trypsin and chymotrypsin. 6. The evolutionary ancestry of these enzymes is discussed.