Matrix Metalloproteinase 7 (MMP7) is a member of the matrix metalloproteinases (MMPs) family which are zinc and calcium dependent endopeptidases. Structurally, MMP-7 is the smallest of the MMPs and consists of two domains: a pro-domain that is cleaved upon activation and a catalytic domain containing the zinc-binding site. MMP-7 (matrilysin) is expressed in epithelial cells of normal and diseased tissues, and is capable of digesting a large series of proteins of the extracellular matrix including collagen IV and X, gelatin, casein, laminin, aggrecan, entactin, elastin and versican. Thus we have chosen casein-zymography to measure the activity of MMP7. Briefly, various concentrations of MMP7 (10ug, 5ug, 1ug, 0.1ug ,0.01ug) were denatured by SDS loading buffer, electrophoresed through sodium dodecylsulphat-polyacrylamide gel (SDS-PAGE; 15% gels) containing casein (1 mg/ml) with nonreducing conditions. After renaturation, incubation and CCB-stained, active MMP7 would hydrolyze casein nearby, which was indicated by the white bands on the gel. In this experiment, we use heat-denatured MMP7 protein as negative control, and trypsin (1ug/ml) as positive control. The result was shown in figure 1.