Calcium-activated neutral protease. Its localization in the myofibril, especially at the Z-band

Calcium-activated neutral protease (CANP) was demonstrated in myofibrils, especially at the Z-band in chicken glycerinated myofibrils, by an immunofluorescent method. The amount of CANP bound to myofibrils was approximately 4 percent of that contained in the whole muscle homogenate. No immunological difference was recognized between the myofibril-bound CANP and the soluble one when examined by Ouchterlony's immunodiffusion analysis. A possible role of myofilbril-bound CANP in the physiological turnover of the myofibrillar proteins is discussed.