DNA strongly impairs the inhibition of cathepsin G by alpha(1)-antichymotrypsin and alpha(1)-proteinase inhibitor

• Published in: The Journal of biological chemistry Vol. 275; no. 6; pp. 3787 - 3792
• Main Authors: Duranton, J, Boudier, C, Belorgey, D, Mellet, P, Bieth, J G
• Format: Journal Article
• Language: English
• Published: United States 11.02.2000
• Subjects: alpha 1-Antichymotrypsin - pharmacology; alpha 1-Antitrypsin - pharmacology; Cathepsin G; Cathepsins - antagonists & inhibitors; Chromatography, Affinity; DNA - pharmacology; DNA-Binding Proteins - pharmacology; Humans; Kinetics; Lung - metabolism; Neutrophils - enzymology; Oligodeoxyribonucleotides - pharmacology; Proteinase Inhibitory Proteins, Secretory; Proteins - pharmacology; Serine Endopeptidases
• ISSN: 0021-9258
• DOI: 10.1074/jbc.275.6.3787

This paper explores the possibility that neutrophil-derived DNA interferes with the inhibition of neutrophil cathepsin G (cat G) and proteinase 3 by the lung antiproteinases alpha(1)-proteinase inhibitor (alpha(1)PI), alpha(1)-antichymotrypsin (ACT), and mucus proteinase inhibitor (MPI). A 30-base pair DNA fragment ((30bp)DNA), used as a model of DNA, tightly binds cat G (K(d), 8.5 nM) but does not react with proteinase 3, alpha(1)PI, ACT, and MPI at physiological ionic strength. The polynucleotide is a partial noncompetitive inhibitor of cat G whose K(i) is close to K(d). ACT and alpha(1)PI are slow binding inhibitors of the cat G-(30bp)DNA complex whose second-order rate constants of inhibition are 2300 M(-1) s(-1) and 21 M(-1) s(-1), respectively, which represents a 195-fold and a 3190-fold rate deceleration. DNA thus renders cat G virtually resistant to inhibition by these irreversible serpins. On the other hand, (30bp)DNA has little or no effect on the reversible inhibition of cat G by MPI or chymostatin or on the irreversible inhibition of cat G by carbobenzoxy-Gly-Leu-Phe-chloromethylketone. The polynucleotide neither inhibits proteinase 3 nor affects its rate of inhibition by alpha(1)PI. These findings suggest that cat G may cause lung tissue destruction despite the presence of antiproteinases.