Effect of a serine protease on isolated myofibrils

Morphological changes occurred in myofibrils prepared from the glycerinated psoas muscle of rabbit during incubation with a serine protease crystallized from rat skeletal muscle. Two notable phenomena were observed: (1) loss of the Z band in the early stage of incubation and (2) complete disappearance of the A band after swelling of the myofibrils. The results indicate that the serine protease has an action on myofibrils different from that of Ca2+-dependent neutral protease.