Review

The current status of calpain research is summarized on the basis of the most recent results. The main points are as follows. (i) Calpain constitutes a large family. (ii) Ca2+ ions cause the dissociation of calpain into subunits and the resulting free 80 kDa subunit is the active form of the enzyme. This dissociation corresponds to the activation of calpain. (iii) Some powerful clues have been obtained that will be helpful for analyzing the physiological function.