Regulation of Protein and Amino Acid Degradation in Skeletal Muscle,
HARVARD MEDICAL SCHOOL BOSTON MASS DEPT OF PHYSIOLOGY
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The article reviews recent investigations on the following aspects of protein metabolism in muscle 1 In muscle the average rates of protein catabolism vary under different physiological conditions, e.g. fasting. Several factors have been found to reduce protein catabolism, including insulin, glucose, and branched chain amino acids. In addition, repeated contractions and passive tension on the muscle retard net proteolysis. 2 Muscle rapidly oxidizes 3 required amino acids - leucine, isoleucine, and valine. This process increases severalfold upon fasting, in diabetes, and after hypophysectomy. 3 Muscle releases into the circulation large amounts of alanine. This process is linked to degradation of the branched chain amino acids. Since alanine is a major precursor for glucose synthesis in liver and since liver releases branched chain amino acids selectively during gluconeogenesis, there appears to be a cycle between muscle and liver of branched chain amino acids and alanine.
- Anatomy and Physiology