Purification of a type V collagen degrading metalloproteinase from rabbit alveolar macrophages

A proteinase capable of degrading the helical region of native human type V collagen was identified in serum-free culture medium from "in vivo-activated" rabbit alveolar macrophages. This enzyme was purified to homogeneity using a combination of gel-filtration, ion-exchange and affinity chromatography. Analysis of the purified material by gel electrophoresis revealed a single broad band with relative molecular mass of 82,000 daltons Enzyme activity was eluted from the gel in a region corresponding to the stained band. The protein band was also found to stain positively using the periodic acid-Schiff technique indicating that it was glycosylated. Amino acid analysis revealed a composition rich in acidic residues. The enzyme cleaved type V collagen into three large molecular weight doublets consistent with two cleavage sites within the helix but was inactive against native type I collagen. However, when type I or type V collagen was heat-denatured, the enzyme degraded the alpha chains to small molecular weight peptides.