Cathepsins are a class of globular lysosomal proteases playing a vital role in mammalian cellular turnover. They degrade polypeptides and are distinguished by their substrate specificities. Cathepsin S is a cysteine proteinase involved in the pathogenesis of autoimmune diseases, atherosclerosis, cancer, obesity and related diseases.The SensoLyte® 520 Cathepsin S Activity Assay Kit uses a 5-FAM/QXL^®520 labeled FRET peptide substrate for measurement of enzyme activity. In the intact FRET peptide, the fluorescence of 5-FAM is quenched by QXL^® 520. Upon cleavage of the FRET peptide by the active enzyme, the increase of fluorescence can be continuously monitored at excitation/emission = 490 nm/520 nm. With superior fluorescence quantum yield and longer emission wavelength, the 5-FAM/QXL^® 520 based FRET peptide shows less interference from the autofluorescence of test compounds and cellular components and provides better assay sensitivity. The kit can be used to detect the activity of Cathepsin S enzyme in biological samples and purified enzyme preparations. The kit contains: • 5-FAM/QXL^®520-based FRET peptide substrate (Ex/Em=490/520 nm upon cleavage)• Assay buffer • Human spleen Cathepsin S • Inhibitor • Fluorescence reference standard for calibration • A detailed protocol

Kit size: 100 assays (96-well plate)