Serine protease in mice with hereditary muscular dystrophy.

The activities of serine protease, cathepsin B1, ornithine aminotransferase, and aldolase in skeletal muscles of mice with hereditary muscular dystrophy and their normal litter mates were studied. In dystrophic muscle, the specific and total activities of serine protease were much higher than in normal muscle, and the specific activities, but not the total activities, of cathepsin B1 and ornithine aminotransferase were twice those in normal muscle, and several new fragments, which are normally formed by limited proteolysis, were found in dystrophic muscle. When myofibrillar proteins of normal and dystrophic muscles were incubated with highly purified serine protease, their myosin, alpha-actinin and tropomyosin disappeared completely.