Proteoglycan-degrading metalloproteases of human articular cartilage.

Two metalloproteases have been purified from human articular cartilage. These attack the core protein of proteoglycan with pH optima of 5.3 and 7.2. The acid protease retains 40% of its activity at physiological pH. The two proteases are related in their properties of latency, activation, substrate specificity, and inhibitor pattern. They differ in pI, pH optimum, molecular weight, calcium requirement, and action on gelatin. Both activities are elevated 3-5 fold in osteoarthritic cartilage. Both proteases attack Ala-Leu and Tyr-Leu bonds in the B-chain of insulin. It is postulated that the entire family of metalloproteases acting on extracellular matrix shares a common specificity for Gly(Ala)-Leu(Ile) bonds.