Porcine pancreatic cationic pro-elastase. Studies on the activation, turnover and interaction with plasma proteinase inhibitors

Porcine pancreatic cationic pro-elastase was partly purified from pancreatic juice. The pro-enzyme binds slowly to alpha-macroglobulin and alpha 1-proteinase inhibitor. After 24 h incubation with plasma at room temperature more than 50% of the pro-elastase was still recovered in the form of free pro-enzyme. The pro-enzyme was activated by trypsin at neutral pH and by cathepsin B at pH 3.8. In the pig the half-life of i.v. administered pro-enzyme was about 30 min. After injection into the pancreatic duct radioactively labelled pro-elastase appeared in plasma within 30 min, and in peritoneal fluid after about 1 h.