Effect of DNase on the activity of neutrophil elastase, cathepsin G and proteinase 3 in the presence of DNA

It has been shown previously that DNA binds and inhibits neutrophil elastas e (NE). Here we demonstrate that DNA has a better affinity for neutrophil c athepsin G (cat G) than for NE and is a better inhibitor of cat G than of N E. DNase-generated < 0.5 kb DNA fragments inhibit NE and cat G as potently as full length DNA, This rationalises our observation tl;at administration of DNase to cystic fibrosis patients does not enhance the NE and cat G acti vity of their lung secretions. Neutrophil proteinase 3 is not inhibited by DNA and might thus be the most harmful proteinase in inflammatory lung dise ases. (C) 2000 Federation of European Biochemical Societies.