Serine Proteinase and Serine Proteinase Inhibitors of Normal and Degenerate Knee Joint Menisci

Knee joint menisci were obtained at the time of autopsy from Caucasians of ages greater than 40 years. Menisci were extracted using 6 M urea containing 10 mM mercaptoethanol. Fractions obtained by gel filtration on Sephadex G-100 superfine were shown to contain a distinct gelatinolytic enzyme which also could degrade fibrinogen. By means of specific inhibitors this enzyme was assigned to the serine proteinase classification. Fractionation of extracts on Sephadex G-50 superfine were found to possess trypsin and plasmin inhibitory activity, but did not inhibit porcine pancreatic elastase. Degenerated menisci contained enhanced gelatinolytic activity but no detectable trypsin inhibitory activity. The meniscal proteinase(s) were completely inhibited by the trypsin inhibitor also present in the normal tissues. On SDS-polyacrylamide gel electrophoresis meniscal serine proteinase had an apparent molecular weight of 24,000 daltons, whereas the molecular weight of meniscal trypsin inhibitor was approximately 7,000 daltons.