Essential amino acids of the prawn.

The essential amino acids of the prawn Penaeus japonicus were investigated by a radio-isotopic method using [3H] acetate, the incorporation of radioactivity into the constituent amino acids of protein fraction was examined by column chromatography on Amberlite IR-120, followed by the radioactivity measurement. Radioactivity was unambiguously incorporated inot aspartic acid, serine, glutamic acid, praline, glycine, alanine, and cysteic acid. These amino acids were suspected to be unnecessary for the prawn. On the other hand, little or no radioactivity was incorporated into valine, methionine, isoleucine, leucine, pheylalanine, lysine, histidine, arginine, ghreonine, and tryptophan. We inferred that these 10 amino acids are not synthesized de novo and are probably essential for the growth of the prawn. Tyrosine was thought to be formed from the ingested phenylalanine.