Myofibrillar creatine kinase in Duchenne and avian muscular dystrophy

The presence and activity of the fraction of creatine kinase (CK) which was associated with myofibrils and located in the M line of the sarcomeres was determined in normal and dystrophic avian muscle and in normal and dystrophic (Duchenne) human muscle. Myofibrils were isolated from homogenates of muscle and washed nine times so as to remove nonmyofibrillar CK. In myofibrils from dystrophic muscle the enzyme CK was localized to the M line using immunofluorescent techniques and was enzymatically active. These results suggest that in both avian and Duchenne muscular dystrophy, there is not a myofibrillar disorder of the phosphocreatine shuttle.