The Amino Acids Required for Growth in Mice and the Availability of their Optical Isomers

Abstract

Moderate growth was obtained in mice fed mixtures of twenty purified amino acids as the source of protein nitrogen. Both optical forms of methionine and phenylalanine, but only the natural forms of valine, leucine, isoleucine, and threonine, could be utilized for this purpose. The rate of growth was not retarded by the removal of arginine. Evidently, therefore, the mouse is able to synthesize arginine at a fairly rapid rate. Slow growth occurred when the source of protein nitrogen was limited to the seven amino acids named above and lysine, tryptophane, and histidine. Hence, none of the ten amino acids omitted from the latter mixture could have been absolutely indispensable.