Studies on the D-alanine in the aquatic animals

近年来，在许多水生动物体内检测到高水平的游离d -丙氨酸，但对游离d -丙氨酸积累的生化机制知之甚少。本研究旨在积累更多关于d -丙氨酸在水生动物中的分布的信息。对日本对虾（Penaeus japonicus）尾肌80%乙醇提取物中d -丙氨酸和l -丙氨酸等氨基酸进行了分析。所有虾尾肌总丙氨酸水平均为4 ~ 20 μmol/g，但D-丙氨酸与总丙氨酸的浓度比（D/D+L）为0.42 ~ 0.47，与换壳周期相同。甘氨酸含量显著，分别为87 ~ 195μmol/g。牛磺酸和丙氨酸在无脊椎动物中含量丰富，相对较低。脱皮前虾游离氨基酸总量（225 ~ 324μmol/g）增加。谷氨酰胺、脯氨酸和精氨酸在蜕皮前的虾中也有所增加。另一方面，脱壳后虾的甘氨酸含量增加。以l -丙氨酸和d -丙氨酸为底物，对poecllonotus、T. nlphobles、T. pardahs和T. rubrlpes的肝脏和卵巢粗酶溶液中丙氨酸消旋酶活性进行了测定。所有标本肝脏中均有D-to-L方向的活性。这种活动在T类动物中最为强烈，其次是Taklfugu poecilonotus和T. pardalis。黄花田鼠子房丙氨酸消旋酶仅在D-to-L方向表现出极低的活性，而红田鼠子房则没有。这些结果表明，河豚可以利用饲料中的d -丙氨酸残留物。

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.