Abstract
1. 1. Activity of endogenous proteases in the muscles of various vertebrates was measured over a wide pH range. Three distinct regions of autolysis was found at acid, neutral and alkaline pH range. The activity in the latter pH was observed only in rat. mouse, and to a smaller extent in dog and human skeletal muscles. 2. 2. In the rat muscle the amount and size of peptides formed during autolysis as well as distribution of autolytic activity in the subcellular fractions was determined. 3. 3. Proteases working at acid pH range and localized in lyzosomes seem to degrade chiefly soluble sarcoplasmic and not myofibrillar proteins. 4. 4. Autolytic activity at alkaline pH is present in 0–600 g fractions. This protease degrades all myofibrillar proteins. Its activity is inhibited almost completely by diisopropyl-fluorophosphate and soy-bean trypsin inhibitor, partially by l-I-tosylamidophenylethylchloromethylketone and by injection of rats with the preparation “48/80”. All the results indicate that the alkaline protease is a chymotrypsin-like protease of mast-cell origin. 5. 5. The results suggest that at neutral pH range another proteolytic system is active in muscle. although its activity is rather low.
Published Version
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