D-Amino acids as source of non-specific nitrogen for growth of rats.

Abstract

SummaryRats fed a diet containing physiological amounts of essential L-amino acids but lacking non-essential amino acids grew at a slow rate. Growth rate was increased by increasing concentration of all essential amino acids. Feeding a mixture of DL-amino acids in comparable amounts resulted in growth retardation of animals. Growth inhibition produced by the racemic mixture was traced to an isoleucine deficiency resulting from inclusion of DL-isoleucine, which was actually a mixture of all 4 isomers, thus effectively diluting the active isomer. Substitution of L-isoleucine or a mixture of L- and D allo-isoleucine for the racemic compound in the DL mixture entirely overcame inhibition and produced growth comparable to that obtained with L-amino acids. The experiments provide evidence that D-amino acids can be effectively used as source of nitrogen for biosynthesis of non-essential amino acids.