Matrix metalloproteinases (MMPs) belong to a family of secreted or membrane-associated proteins capable of digesting extracellular matrix components. MMP-13 (collagenase-3, rat collagenase) is involved in quite a few diseases such as arthritis and asthma. The SensoLyte® 520 MMP-13 Assay Kit uses a 5-FAM (fluorophore) and QXL™ 520 (quencher) labeled FRET peptide substrates for continuous measurement of the enzyme activities. In an intact FRET peptide, the fluorescence of 5-FAM is quenched by QXL™ 520. Upon the cleavage of the FRET peptide by MMP-13, the fluorescence of 5-FAM is recovered, and can be continuously monitored at excitation/emission = 490 nm/520 nm. With superior fluorescence quantum yield and longer emission wavelength, 5-FAM/QXL™ 520 based FRET peptide is less interfered by the autofluorescence of test compounds and cellular components and provides better assay sensitivity. The assays are performed in a convenient 96-well or 384-well microplate format. Members of the MMP family have poor substrate sequence specificity, making it difficult to use a peptide substrate alone to differentiate the activity of a particular MMP from other MMPs. If several MMPs are coexisting in your samples and you would like to specifically measure MMP-13 activity, please choose the SensoLyte® Plus MMP-13 Assay Kit, Cat# 72019.