The calpains are a family of intracellular Ca2+ dependent cysteine proteases. The best-characterized calpains are isoforms 1 (m) and 2 (m). Calpains respond to Ca2+ signals by cleaving many specific proteins, thereby irreversibly modifying their function(s). They are implicated in a variety of Ca2+ regulated cellular processes as well as various pathological phenomena, such as ischemic injury, muscular dystrophy, diabetes, cataract, atherosclerosis, Alzheimer’s disease, and cancer. Calpains represent potential therapeutic targets for drug discovery. The SensoLyte® AMC Calpain Assay Kit is optimized for detecting calpain activities. This kit contains a fluorogenic peptide substrate, suc-LLVY-AMC. Upon calpain protease cleavage, suc-LLVY-AMC generates the AMC fluorophore emitting bright blue fluorescence and can be monitored at excitation/emission=354/442 nm. Increase in AMC fluorescence is proportional to calpain activity. The assay can detect both calpain 1 (µ) and 2 (m) activities and is ideal for kinetic study of these enzymes. The assays are performed in a convenient 96-well microplate format.