GENERATION OF MATRIX-DEGRADING PROTEOLYTIC SYSTEM FROM FIBRONECTIN BYCATHEPSIN-B, CATHEPSIN-G, CATHEPSIN-H AND CATHEPSIN-L

By their endoproteinase activities, cathepsins B, G, H and L can gener ate matrix-degrading proteolytic system from fibronectin. All four cat hepsins studied cleaved fibronectin in fragments that were either prot eolytically active or activated after incubation at pH 7.4 and in the presence of Ca2+. The highest enhancement of the matrix protein-degrad ing activity was observed after a gelatin-affinity chromatography of e ach digest. These results suggest that the effect of cathepsins at phy siological pH in vivo may be enhanced by the activation of a matrix-de grading proteolytic system from fibronectin.