Distribution of free D-amino acids in the tissues of crustaceans

Free D-amino acids were determined in the tissues of crustaceans, three macrurans and four brachyurans, using reversed-phase ion-pair HPLC after derivatization with (+)-1-(9-fluorenyl)ethyl chloroformate. Of several D-amino acids detected, D-alanine was the most abundant and widely distributed among every tissue of crustacean species determined. The content of D-alanine in the muscle of these crustaceans ranged from 3.2 to 16.8 mu mol/g wet weight. The percentage of D-alanine to total alanine reached 31.7% on average. The second predominant D-amino acid was D-arginine which was less than 2 mu mol/g and accounted for less than 10% of the total arginine. Acidic amino acids, D-aspartate and D-glutamate, were present only in the tissues of macrurans and the contents were less than 1 mu mol/g. The percentage of D-aspartate to total aspartate, however, varied from 12 to 70%. Several other D-amino acids were also detected in small quantities and low percentages.