Interaction Between Human Pancreatic Elastase and Plasma Protease Inhibitors

Abstract

Human serum (1 ml) inhibits about 0.9 mg of purified human pancreatic elastase owing to complexation with .alpha.1-antitrypsin and .alpha.2-macroglobulin. On addition to serum, elastase is preferentially bound by .alpha.2-macroglobulin. The complexes between elastase and .alpha.1-antitrypsin and .alpha.2-macroglobulin, respectively, migrate as .alpha.2-globulin on agarose gel electrophoresis. Elastase bound by .alpha.1-antitrypsin is precipitated by antibodies against enzyme as well as inhibitor, while the .alpha.2-macroglobulin-bound elastase is only precipitated by antibodies against the inhibitor. The molar combining ratio for elastase/.alpha.1-antitrypsin is 1:1 and for elastase/.alpha.2-macroglobulin 2:1. The elastase bound by .alpha.2-macroglobulin retains its activity against low MW substrates, while that bound by .alpha.1-antitrypsin is enzymologically inactive.