Is elastomucoproteinase a double-headed enzyme?

During isolation pancreatic elastase is accompanied by a minor component, elastomucoproteinase (EMPase), which can be separated in pure state by anion-exchange chromatography. EMPase exhibits both proteolytic and mucolytic activities. Applying powdered aortic preparations as a substrate, the enzyme can split off carbohydrate moieties, but it can also cleave peptide bonds as a proteinase. Assaying with tripeptide-p-nitroanilide substrates, the enzyme can decompose only those substrates which contain Phe or Tyr at the C-terminal. It appeared that the binding of Bz-Ala-Gly-Phe-pNA was the best, while the hydrolysis of Bz-Ala-Pro-Tyr-pNA was the fastest. Proteolytic activity of EMPase can be completely inhibited with phenylmethanesulphonyl fluoride, whereas its mucolytic activity only by 20%. The two activities may be located at two separate sites. The enzyme seemed to be composed of a single polypeptide chain by SDS-gel electrophoresis in the presence of urea and beta-mercapto-ethanol.