Mucus proteinase inhibitor: a fast-acting inhibitor of leucocyte elastase.
Human mucus proteinase inhibitor is a fast-acting inhibitor of human leucocyte elastase (EC 3.4.21.37) and forms a stable, complex with this enzyme. At physiological ionic strength and temperature and in the presence of 10 mg/ml albumin, the kinetic constants characterizing the interaction between elastase and the non-degraded inhibitor are: kass = 6.4.10(6) M-1.s-1, kdiss = 2.3.10(-3) s-1, Ki = 3.10(-10) M. The partially degraded inhibitor isolated by chymotrypsin-Sepharose chromatography inhibits elastase with similar efficiency, suggesting that if partial proteolysis of the inhibitor occurs in vivo, the latter may still act as a potent antielastase. Mucus proteinase inhibitor therefore plays a physiological antielastase function in upper respiratory tract secretions, since it inhibits elastase with a delay time of 150 ms and behaves like an irreversible inhibitor.
Boudier
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INSERM Unité 237, Université Louis Pasteur de Strasbourg, Faculté de Pharmacie, Illkirch, France.
Bieth
J G
JG
D006801:Humans; D007700:Kinetics; D007962:Leukocytes / Q000201:enzymology; D009093:Mucus / Q000201:enzymology*; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011480:Protease Inhibitors / Q000378:metabolism*; D011485:Protein Binding
D011480:Protease Inhibitors; D010196:Pancreatic Elastase