Abstract
We have isolated an activator of collagenase from medium conditioned with articular cartilage. The activity is contained in an acidic protein appearing as a doublet band of M r 57,000 and 56,000 on sodium dodecyl sulfate polyacrylamide gels. Both components of the doublet have identical isoelectric points as demonstrated by gel electrophoresis. Purified synovial collagenase has a high dependence on the presence of this factor for activity. Other known activators of latent proteolytic enzymes such as trypsin and mercurials will stimulate collagenase but only if activator protein is present. The activator protein is itself a latent metalloprotease because in the presence of p-aminophenyl-mercuric acetate and calcium it will digest casein. The caseinase activity and collagenase activation activity have identical heat inactivation profiles, both being stable to a temperature of 60 °C and partially inactivated at 80 °C. The synthesis of the activator is localized in the superficial zone of articular cartilage.
Published Version
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