Term for calcium ion-dependent, papain-like cysteine proteases.
Calpains are found in humans and animals. They play a role in the development of very different diseases, e.g. Duchenne's muscular dystrophy, hereditary epidermolysis (see below Epidermolysis bullosa simplex with mutation in plectin isoform 1a), age-related cataracts, rheumatic diseases, type 2 diabetes and circulatory disorders. Several oncogenes and tumor suppressor gene products are substrates for calpaine. The Ca2+-activated protease calplain processes the interleukin-1 alpha precursor into its mature 17 kDa form (see also interleukin-1 alpha).