Extracts of human articular cartilage contain an inhibitor of tissue metalloproteinases

When human articular cartilage is extracted with 2M-guanidinium hydroxychloride at pH 7.5, an inhibitor is obtained that blocks the activity of three metalloproteinases, including collagenase. Molecular-sieve chromatography of the inhibitor gives an M(r) value for the inhibitor of 28 500. The inhibitor is stable to heat (60°C, 1 h) and acid (pH2, 24°C, 10 min). It is destroyed by trypsin and by reduction and alkylation. It is slowly inactivated by aminophenylmercuric acetate. It binds to concanavalin A-Sepharose and it eluted with α-D-l-O-methyl glucopyranoside. Complexes of enzyme and inhibitor are not re-activated by aminophenylmercuric acetate and only partially so by high levels of trypsin. These properties indicate that this inhibitor is a member of the TIMP (tissue inhibitor of metalloproteinases) class. Such an inhibitor previously found in tissue culture and amniotic fluid, is now shown to be directly extractable from tissue.