Kinetic and chemical evidence for the inability of oxidized alpha 1-proteinase inhibitor to protect lung elastin from elastolytic degradation.

The oxidation of human alpha 1-proteinase inhibitor results in the conversion of this protein into a form which cannot protect lung elastin from degradation by elastolytic proteinases. Data indicate that this is primarily because of the lowering of the association rate between the modified inhibitor and neutrophil elastase, as well as in a change in Ki from near 10(-14) to near 10(-10)M. This is consistent with the hypothesis that oxidation of alpha 1-proteinase inhibitor in the lung by cigarette smoke results in a lowering of the protection of this organ from elastolytic degradation.