Enzymatic reduction of oxidized alpha-1-proteinase inhibitor restores biological activity.

Abstract
The major serum inhibitor of proteolytic activity, .alpha.-1-proteinase inhibitor (.alpha.-1-PI), (or .alpha.-1-antitrypsin) can be readily inactivated by oxidation. This inactivation [implicated in lung tissue destruction in emphysema] appears to be due to the oxidation of a critical methionine(s) in .alpha.-1-PI that is required for the inhibition of [dog neutrophil] elastase activity. An enzyme from Escherichia coli that reduces methionine sulfoxide residues in protein can restore the biological inhibitory activity of canine oxidized .alpha.-1-PI.