The exposed linker accounts for the difficulty in purifying full-length collagenase. The C-terminal domain provides a structural model for haemopexin and its homologues. It controls the specificity of MMPs, affecting both substrate and inhibitor binding, although its role remains obscure. These structural results should aid the design of site-specific mutants which will reveal further details of the specificity mechanism.

Objective. To study the interaction of interleukin-la (IL-la) and oncostatin M (OSM) in promoting cartilage collagen destruction.Methods. Bovine, porcine, and human cartilage and human chondrocytes were studied in culture. The levels of collagenase (matrix metalloproteinase 1 [MMP-I]) and tissue inhibitor of metalloproteinases 1 (WMP-1) were measured by bioassay and enzyme-linked immunosorbent assay (ELISA). The levels of OSM in rheumatoid synovial fluid were measured by ELISA.Results. When combined with OSM, 1L-la, ILlp, and tumor necrosis factor a released proteoglycan and collagen from cartilage. OSM was the only member of the IL-6 family to have this effect. Human tendon also responded to IL-la and OSM. OSM increased the production of MMP-1 and TIMP-1 but when combined with IL-la, synergistically promoted MMP-1 production in human chondrocytes and synovial fibroblasts. High levels of OSM were found in human rheumatoid synovial fluids, and confocal microscopy showed that OSM was produced by macmphages in rheumatoid synovial tissue. Conclusion. These results highlight an important

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The primary agents responsible for cartilage and bone destruction in joint diseases are active proteinases that degrade collagen and proteoglycan. All four main classes of proteolytic enzymes are involved in either the normal turnover of connective tissue or its pathological destruction. These proteinases are made by different cells found within the joints. Both extracellular and intracellular pathways exist and individual enzymes can be inhibited by specific proteinaceous inhibitors that block their activity. Recent research has implicated the matrix metalloproteinases (MMPs) in many of the processes involved in joint diseases. The metalloproteinases are capable of degrading all components of the extracellular matrix. This family of proteinases contains a group of at least three collagenases that are capable of degrading native fibrillar collagen. Collagen degradation within joint disease is recognized as the irreversible step in the destruction of cartilage that leads to a failure in joint function. The collagenases are the enzymes necessary to initiate collagen turnover in normal connective tissue turnover and in disease.

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