Determination of pancreatic elastase with new chromogenic substrates-p-nitroanilides of N-acyltripeptides.

Mal-, Suc- and Glt-(Ala)3-NAp were prepared as new substances for determining pancreatic elastase. The kinetic constants show them to be more satisfactory than the previously described Ac-(Ala)3-NAp. The mean elastase output values after pancreozymin and secretin stimulation of the exocrine pancreas were significantly higher in the control subjects than in patients in whom other secretion values were altered. In agar electrophoresis, hog pancreatic elastase (Merck) formed a single cathodal fraction. One cathodal and one anodal fraction were found in human duodenal contents. Serum, plasma, alpha1-antitrypsin and alpha2-macroglobulin inhibit pancreatic elastase. Elastase-alpha1-antitrypsin complexes are enzymatically inactive, whereas the enzymatic activity of elastic-alpha2-macroglobulin complexes is partly preserved. Both types of complexes are stable and are not dissociated to a major extent in the presence of an excess amount of the other inhibitor.