The calpains, calcium-activated neutral proteases, are nonlysosomal, intracellular cysteine proteases. The mammalian calpains include ubiquitous, stomach-specific, and muscle-specific proteins. The ubiquitous enzymes consist of heterodimers with distinct large, catalytic subunits associated with a common small, regulatory subunit. This gene encodes the large subunit of the ubiquitous enzyme, calpain 1. Several transcript variants encoding two different isoforms have been found for this gene.,CAPN1,CANP,CANP1,CANPL1,SPG76,muCANP,muCL,calpain 1,Signal Transduction,Cell Biology & Developmental Biology,Apoptosis,Ubiquitin,Immunology & Inflammation,T Cell Receptor Signaling Pathway,Neuroscience,Calcium Signaling,Neurodegenerative Diseases,Amyloid Plaque and Neurofibrillary Tangle Formation in Alzheimer's Disease,CAPN1