Influence of elastin on the inhibition of leucocyte elastase by α1-proteinase inhibitor and bronchial inhibitor. Potent inhibition of elastin-bound elastase by bronchial inhibitor

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Abstract
We have investigated the effect of human lung elastin on the inhibition of human leucocyte elastase by human .alpha.1-proteinase inhibitor and bronchial inhibitor. Elastin was unable to dissociate the elastase-inhibitor complexes during the 150 min of the elastolysis reaction. When elastase was added to mixtures of elastin and .alpha.1-proteinase inhibitor, it was fully bound to the later. The competition between elastin and bronchial inhibitor was also in favor of the latter, but a 1.5 molar excess of inhibitor over elastase was required to achieve total binding of the enzyme. About 25% of elastin-bound elastase was found by be resistant to the inhibitory effect of .alpha.1-proteinase inhibitor. The major isoenzyme and the mixture of the three minor isoenzymes of elastase exhibited similar behavior. By contrast, bronchial inhibitor was as efficient in inhibiting the elastin-bound elastase as it was in inhibiting the free enzyme. This inhibitor was also able to inhibit fully the fraction of elastin-bound elastase that was resistant to .alpha.1-protease inhibitor. We also describe a rapid procedure for the isolation of gram quantities of .alpha.1-proteinase inhibitor.