Distribution and metabolism of neuroexcitatory amino acids in aquatic organisms

研究了47种海藻和28种海洋动物不同组织中n -甲基- d、l-天冬氨酸（NMA）、kainic酸（KA）和软骨藻酸（DA） 3种神经兴奋性氨基酸的含量。在海藻中，几种蓝藻科和红藻科藻类中检测到极少量的NMA，但在褐藻科藻类中未检测到NMA。在3种中检测到KA，在4种中检测到DA，均属于红藓科（陶门，红藓科）。在rhodomelacean藻类中，就本研究而言，KA和DA仅在日本西南岛屿（德野岛和冲绳本岛）采集的几个特定物种中检测到。值得注意的是，KA和DA的分布都被严格限制在亚热带有限地区的有限种类的某些藻类中。在海洋动物中，在4种海洋双壳类动物中均发现了NMA，在东京湾采集的1只螃蟹中发现了DA，但在所有动物中均未检测到KA。低兴奋性氨基酸长期剂量的影响应从卫生角度进行研究。研究了血壳刺花中NMDA的生理作用，探讨了NMDA与生理环境条件的关系。NMDA在饥饿、渗透压、厌氧条件下没有变化，但在光照和黑暗条件下急剧下降。这表明NMDA作为一种神经递质在双壳类动物中具有重要的作用。血壳示踪实验未证实d -天冬氨酸生物合成NMDA的途径。因此，我们应该检查另一种生物合成途径。

Contents of three neuroexcitatory amino acids, N-methyl-D,L-aspartic acid (NMA), kainic acid (KA) and domoic acid (DA) were investigated in 47 marine algae species and various tissues of 28 marine animals. In marine algae, NMA was detected in very small amounts in several marine algae belonging to Chlorophyceae and Rhodophyceae, but not in algae belonging to Phaeophyceae. KA was detected in three species and DA was detected in four species all belonging to the family Rhdomelaceae (Ceramiales, Rhodophyceae). Among rhodomelacean algae, as far as investigated in this study, KA and DA were detected only in the several particular species collected only in South West Islands of Japan (Tokunoshima Island and Okinawa Main Island). It is noteworthy that the distribution of both KA and DA was strictly restricted within some algae of limited species of limited subtropical area. In marine animals, NMA was found in four species of marine bivalves all belonging to the family Arcidae, DA was found in only one crab collected in Tokyo bay, but KA was not detected in all animal species analyzed. Effect of long term dose of low excitatory amino acids should be investigated from hygienic view point.Concerning the physiological roll of NMDA in blood shell Scapharca broughtonii, the relation of NMDA and physiological and environmental condition was investigated. NMDA did not change by starvation, osmotic pressure, anaerobic condition, but drastically decreased during light and dark circumstance. This would be indicated that NMDA have some important roll as a neurotransmitter in the Arcidae bivalves.Biosynthetic pathway of NMDA from D-aspartic acid was not confirmed by tracer experiment of blood shell. We should therefore check another biosynthetic pathway.