Activation of matrix metalloproteinase 3 (stromelysin) and matrix metalloproteinase 2 ('gelatinase') by human neutrophil elastase and cathepsin G

The ability of human neutrophil elastase and cathepsin G to activate matrix metalloproteinase 3 (MMP-3 = stromelysin) and MMP-2 ('gelatinase') purified from human rheumatoid synovial fibroblasts in culture was examined. The zymogen of MMP-3 (proMMP-3) was activated to full activity with elastase and cathepsin G by limited proteolysis of the molecule into two active forms of M_r ∼ 45000 and M_r ∼ 25000. In contrast, proMMP-2 was not activated at all by these neutrophil serine proteinases, although it was degraded into small fragments. These data suggest that neutrophil elastase and cathepsin G may play an important role in the activation of proMMP-3 in vivo in various inflammatory conditions, but proMMP-2 may be activated in different ways.