Collagenolytic cathepsin activity in rabbit peritoneal polymorphonuclear leucocyte granules.

Collagenolytic cathepsin activity was detected in lysed rabbit peritoneal polymorphonuclear leucocytes. The pH optimum was around 3, and activity was greatly enhanced by the presence of cysteine and EDTA. Digestion of polymeric collagen resulted in the release of alpha, beta, and gamma-chains. Collagenolytic cathepsin activity was associated mainly with the granule fraction isolated from homogenates by differential centrifugation. The granule fraction was further fractionated by isopycnic density-gradient centrifugation, and the collagenolytic cathepsin activity was shown to be associated with the azurophil and tertiary granules, both lysosome-like organelles.