Secretases are key enzymes involved in the production of beta-amyloid peptides found in extracellular amyloid plaques of Alzheimer's disease (AD). They are considered excellent targets for anti-amyloid treatment of Alzheimer's disease. For analyzing secretase activities and their inhibitors, AnaSpec's assay kits use novel FRET peptide substrates that incorporate our QXLTM quenchers. Our new secretase assay kits demonstrate greatly improved performance over traditional secretase assays.