Human methionine sulfoxide-peptide reductase, an enzyme capable of reactivating oxidized alpha-1-proteinase inhibitor in vitro.

The present study demonstrates the presence of methionine sulfoxide [Met(O)] peptide reductase activity in human lung homogenates and in lysates of polymorphonuclear leukocytes (PMN) and alveolar type II cells. Enzyme activity was not detected in human bronchoalveolar lavage fluid or in pulmonary alveolar macrophage lysates. The Met(O)-peptide reductase derived from PMN is capable of reactivating alpha-1-proteinase inhibitor (alpha 1Pl) oxidized by treatment with chloramine-T or a myeloperoxidase oxidizing system. However, the PMN-derived enzyme does not reactivate alpha 1Pl inactivated by treatment in vitro with aqueous solutions of cigarette smoke plus peroxide. In addition, after the instillation of oxidized human alpha 1Pl into lungs of normal or ozone-tolerant rats, no reactivated alpha 1Pl could be found in the pulmonary lavage obtained from these animals. Finally, patients with chronic obstructive pulmonary disease appear to have normal levels of PMN Met(O)-peptide reductase.