Amino acid-activating enzymes in muscle

Abstract

The "cell-sap" fraction of mouse skeletal muscle incorporated labeled pyrophosphate into adenosine triphosphate in the presence of L-amino acids. Leucine and tryptophan were most effective. Most L-amino acids were active. The relative activities of the individual amino acids were roughly the same when a similar preparation from human skeletal muscle was used. Muscle cell sap from mice with hereditary muscular dystrophy showed on the average less incorporation/mg of protein, although there was large individual variation. The mean percentage incorporation/mg of protein/15 min. was 16.1 and 10.2 respectively for normal and dystrophic mice.