The Neutral Proteases of Human Granulocytes

Abstract

Two electrophoretic variants of a collagenolytic enzyme from the cytoplasmic lysosome‐like granules of leukaemic myeloid cells were purified by chromatography of the granule extract on Sephadex G‐75, Bio Rex 70 and collagen–Sepharose, and electrophoresis on polyacrylamide gel. The granulocyte collagenases degraded native collagen in solution at about neutral pH with the production of the two specific fragments. They also acted on other substrates, such as fibrinogen and proteoglycans. The granulocyte collagenases were inhibited by α 1 ‐antitrypsin and by α 2 ‐macroglobulin. The two collagenases gave reactions of identity on Ouchterlony immunodifusion and crossed immunoelectrophoresis. Amino acid analyses suggested that the collagenases differed only in respect of a few residues. Ultracentrifugation indicated that both proteins were homogeneous and had an s 0 20,w of 4.5 S. Thin‐layer chromatography on Sephadex G‐150 suggested that both collagenases had a molecular weight of 76000. Electrophoresis after treatment of the collagenases with sodium dodecylsulfate revealed two components with molecular weights of 42000 and 33000, respectively, suggesting that the native enzymes are built up of to two subunits.