Specific inhibition of calpain (calcium-dependent cysteine protease). Plays a key role in postmortem tenderization of meat and have been proposed to be involved in muscle protein degradation in living tissue. Additional isoforms seem to exist. Each of the four flexible inhibitory domains can inhibit one calcium-bound calpain molecule by occupying both sides of the active site. The N-terminus is blocked. The disease is caused by variants affecting the gene represented in this entry. Belongs to the protease inhibitor I27 (calpastatin) family. Contaminating sequence. Potential poly-A sequence.