Kinetics of the inhibition of human pancreatic elastase by recombinant eglin c. Influence of elastin.
Recombinant eglin c is a potent reversible inhibitor of human pancreatic elastase. At pH 7.4 and 25 degrees C, kass. = 7.3 x 10(5) M-1.s-1, kdiss. = 2.7 x 10(-4) s-1 and Ki = 3.7 x 10(-10) M. Stopped-flow kinetic indicate that the formation of the stable enzyme-inhibitor complex is not preceded by a fast pre-equilibrium complex or that the latter has a dissociation constant greater than 0.3 microM. The elastase-eglin c complex is much less stable at pH 5.0 and 25 degrees C, where kdiss. = 1.1 x 10(-2) s-1 and Ki = 7.3 x 10(-8) M. At pH 7.4 the activation energy for kass. is 43.9 kJ.mol-1 (10.5 kcal.mol-1). The kass. increases between pH 5.0 and 8.0 and remains essentially constant up to pH 9.0. This pH-dependence could not be described by a simple ionization curve. Both alpha 2-macroglobulin and alpha 1-proteinase inhibitor are able to dissociate the elastase-eglin c complex, as evidenced by measurement of the enzymic activity of alpha 2-macroglobulin-bound elastase or by polyacrylamide-gel electrophoresis of mixtures of alpha 1-proteinase inhibitor and elastase-eglin c complex. The rough estimate of kdiss. obtained with the alpha 2-macroglobulin dissociation experiment (1.6 x 10(-4) s-1) was of the same order of magnitude as the constant measured with the progress curve method. Eglin c strongly inhibits the solubilization of human aorta elastin by human pancreatic elastase. The extent of inhibition is the same whether elastase is added to a suspension of elastin and eglin c or whether elastase is preincubated with elastin for 3 min before addition of eglin c. However, the efficiency of the inhibitor sharply decreases if elastase is reacted with elastin for more prolonged periods.
I.N.S.E.R.M. Unité 237, Faculté de Pharmacie, Université Louis Pasteur de Strasbourg, Illkirch, France.
B
B
Faller
S
S
Dirrig
M
M
Rabaud
J G
JG
Bieth
D004549:Elastin / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010179:Pancreas / Q000201:enzymology*; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors*; D011506:Proteins; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D015843:Serpins; D013696:Temperature; D000515:alpha 1-Antitrypsin / Q000494:pharmacology; D000511:alpha-Macroglobulins / Q000378:metabolism
D011506:Proteins; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D015843:Serpins; D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins; C028656:eglin proteinase inhibitors; D004549:Elastin; D010196:Pancreatic Elastase