Utilization of D-Amino Acids for Growth by Drosophila melanogaster Larvae

Abstract

The capacity of Drosophila melanogaster larvae to utilize the D-forms of the essential amino acids for growth in place of their L-isomers was examined. D-Phenylalanine, D-methionine, and D-histidine, in decreasing order, were the only D-amino acids which were readily used for growth by larvae. The D-forms of arginine, lysine, and valine stimulated larval growth when fed with suboptimal quantities of their L-isomers. D-Isoleucine and D-threonine had little, if any, effect on larval growth. At the levels tested, D-leucine and D-tryptophan inhibited the growth of D. melanogaster larvae. Feeding either glycine, L-cystine, or L-tyrosine in a diet containing the L-isomers of the essential amino acids and L-glutamic acid stimulated larval growth. Larvae appear capable of using D-cystine for growth in place of L-cystine. The ability of D. melanogaster larvae, Tetrahymena pyriformis, and the rat to utilize D-amino acids for growth was compared. Points of evolutionary interest were discussed.