Matrix metalloproteinases (MMPs) belong to a family of secreted or membrane-associated proteins capable of digesting extracellular matrix components. MMP-15 (MT2-MMP) is a member of the membrane-type matrix metalloproteinase (MT-MMP) subfamily, which contains a potential transmembrane domain and is expressed at the cell surface rather than secreted. MMP-15 is responsible for the degradation of basement membrane and it is also an important activator for MMP-2. MMP-15 plays an important role in tumor invasion. The SensoLyte® 520 MMP-15 Assay Kit uses a 5-FAM (fluorophore) and QXL™ 520 (quencher) labeled FRET peptide substrates for the continuous measurement of the enzyme activities. In an intact FRET peptide, the fluorescence of 5-FAM is quenched by QXL™ 520. Upon cleavage of the FRET peptide by MMP-15, the fluorescence of 5-FAM is recovered, and can be continuously monitored at excitation/emission = 490/520 nm. With superior fluorescence quantum yield and longer emission wavelength, 5-FAM/QXL™ 520 based FRET peptide is less i terfered by the autofluorescence of test compounds and cellular components and provides better assay sensitivity. The assays are performed in a convenient 96-well microplate format.