Nutritive effects of d-amino acids on the silkworm, Bombyx mori

Nutritive effects of d-amino acids on the silkworm, Bombyx mori, were investigated by growth experiments using defined diets and also by analysis of free amino acids in the larval haemolymph. None of the d-forms of the usual ten essential amino acids could be utilized effectively, although d-methionine was utilized in lieu of the l-form only to a limited extent and d-histidine gave a positive but smaller effect than d-methionine. d-Proline, its l-form being semi-essential for the silkworm, was not utilized. d-Leucine, and to a lesser extent d-alanine and d-serine, were found to be somewhat toxic. Comparison of free amino acid patterns in the haemolymph of the fifth-instar larvae, which fed on diets either lacking l-forms of histidine, methionine and leucine singly or including the d-forms singly in place of these l-forms, supported the results of the growth experiments.