Serine Protease in Mice with Hereditary Muscular Dystrophy1

Abstract

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. Dystrophic muscle also contained lower specific and total activities of aldolase than normal muscle. Its myofibrillar protein was strikingly different from that of 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, α-actinin and tropomyosin disappeared completely.