alpha 1-Antichymotrypsin in lung secretions is not an effective proteinase inhibitor

This paper presents evidence that alpha 1-antichymotrypsin in lung secretions is not effective as an inhibitor of chymotrypsin-like enzymes. First, lung secretion samples inhibited more cathepsin G on a one-to-one molar basis than could be accounted for by the alpha 1-antichymotrypsin present. Second, the major cathepsin G inhibitory capacity of sputum was in gel filtration fractions that corresponded to a low molecular weight (10,000-15,000) and contained immunoreactive antileucoprotease. Third, although alpha 1-antichymotrypsin purified from plasma was almost fully active against cathepsin G, that purified from lung lavage retained less than 15% of its inhibitory function. Immunoblotting following sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that alpha 1-antichymotrypsin in plasma and lung secretions are of similar molecular size and no enzyme-alpha 1-antichymotrypsin complexes could be detected in sputum or bronchoalveolar lavage fluids. However, in contrast to the alpha 1-antichymotrypsin purified from plasma, the lavage protein gave a broad elution profile following anion-exchange chromatography.