Studies on the D-alanine in the aquatic animals

点击翻译按钮获取中文摘要

Recently, high levels of fee D-alanine were detected in the many aquatic animals, but a little information has been available about the biochemical mechanisms of free D-alanine accumulation. The present studies were planned to accumulate more information on the distribution of D-alanine in aquatic animals.D-and L-alanine and the other amino acids were analyzed in the 80% ethanol extracts from the tail muscles of cultured Kurum shrimp Penaeus japonicus during intermolt cycle. Total alanine levels were 4〜20 μmol/g in the tail muscles of all the shrimp analyzed, although concentration ratio of D-alanine to total alanine (D/D+L), which were 0.42〜0.47, were as the same as during intermolt cycle. Significant amount of glycine was detected, amounting to 87〜195μmol/g, respectively. Taurine and alanine, they are abundant in invertebrates, were comparatively lower. Total of free amino acids (225〜324μmol/g) increased in the premolt shrimps. Glutamine, prorine and argine also increased in the premolt shrimps. On the other hand, glycine increased in the postmolt shrimps.Alanine racemase activities were examined on the crude enzyme solutions from the liver and ovary of Takifugu poecllonotus, T. nlphobles, T. pardahs and T. rubrlpes, using L-alanine or D-alanine as substrates. The activity in the only D-to-L direction is found in liver of all specimens. The activity is most strong in T nlphobles, following Taklfugu poecilonotus and T. pardalis. The ovary of T. niphobles showed week activity of alanine racemase in only D-to-L direction, but not T. rubripes. These results suggest that puffers can use D-alanine remains in feed.