The tissue inhibitors of matrix metalloproteinases (MMPs), TIMP-1 and TIMP-2, are also angiogenesis inhibitors. Cathepsin B and MMPs are found at sites of neovascularization in pathologies such as cancer and osteoarthritis. Treatment of TIMP-1, TIMP-2, and of a mixture of both inhibitors from human articular chondrocytes with cathepsin B resulted in their fragmentation, whereby they lost their MMPinhibitory and anti-angiogenic activities. Our data suggest that, besides directly participating in tissue destruction, cathepsin B can be harmful for two further reasons: it raises the activity of the MMPs also in the absence of mechanisms up-regulating these enzymes, and it stimulates angiogenesis. This is a prerequisite for blood vessel invasion in a variety of pathological situations of which cancer and osteoarthritis are prominent examples.z 1999 Federation of European Biochemical Societies.

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The influence of ionic strength and composition on the binding and inhibition of human leukocyte elastase by glycosaminoglycans with variable degree and position of sulfation was investigated. The kinetic mechanism of inhibition had a hyperbolic, mixed-type character with a competitive component that was promoted by low ionic strength, reduced by phosphate ions, and which also depended on the substrate and glycosaminoglycan structure. Enzyme binding was a cooperative phenomenon that varied with ionic strength and composition. The inhibition patterns correlated with the cationic character of elastase and with the distribution of arginines on its molecular surface, most notably with residues located in the vicinity of the substrate binding region. The order of affinity for elastase binding was chondroitin 4-sulfate < chondroitin 6-sulfate < dermatan sulfate, iduronate-containing derivatives being superior with respect to the glucuronate-containing counterparts. Additional sulfation at both the 4- and 6- positions or at the N- and 4-positions of the N-acetylgalactosamine moiety decidedly improved the inhibitory efficiency. The results highlight a fundamental physiological role of enzyme-glycosaminoglycan interactions. In the azurophil granule of the human polymorphonuclear neutrophil, elastase and other enzymes are bound to a matrix of chondroitin 4-sulfate because this is the only glycosaminoglycan that simultaneously offers good binding for enzyme compartmentalization together with prompt release from the bound state at the onset of phagocytosis.

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