Identification of a type V collagen-degrading enzyme from human sputum

An enzyme capable of degrading type V collagen was found in the sputum of patients with chronic obstructive pulmonary disease (COPD). This enzyme was found in a latent form and was activated by 4-aminophenylmercuric acetate (APMA). Molecular sieve chromatography on Ultrogel AcA-34 and affinity chromatography on type V collagen-Sepharose were successful in separating type V from type I collagenolytic activity. The enzyme became active after affinity chromatography and no longer required activation with APMA to manifest activity. It was found to be a metalloproteinase by virtue of its inhibition by ethylene-diaminetetraacetic acid and phenanthroline but not by phenylmethanesulfonyl fluoride or N-ethylmaleimide. Because degradation of matrix proteins is felt to be important in the pathogenesis of COPD, it is possible that the selective degradation of type V collagen by this enzyme may play a role in the development of COPD.