SensoLyte520 Cathepsin S Assay

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.