Ca-activated neutral protease and its inhibitors: in vitro effect on intact myofibrils

SDS gel electrophoresis of troponin and myosin extracted from chicken myofibrils pretreated with Ca-activated neutral protease showed a pattern similar to that observed in the muscles of patients with Duchenne muscular dystrophy, that is, a decrease in troponin-I and troponin-C with relative preservation of troponin-T and degradation of the heavy chain of myosin. Also, alpha-actinin and troponin-C were released from myofibrils. Two inhibitors of Ca-activated neutral protease, leupeptin and E-64, inhibited the degradative action of Ca-activated neutral protease on intact myofibrils in vitro.