Neutral Proteases of Human Granulocytes III. Interaction between Human Granulocyte Elastase and Plasma Protease Inhibitors

AbstractPurified human granulocyte elastase is inactivated by serum owing to com-plexation with α1-antitrypsin and α2-macroglobulin. The molar combining ratios are 1:1 for elastase/α1-antitrypsin and 2:1 for elastase/α2-macroglobulin. The affinity of granulocyte elastase is approximately the same for both protease inhibitors. Considering the molar concentration of the two inhibitors in normal human plasma, α1-antitrypsin thus is the dominating elastase inhibitor.