Report on my visit to the Institute for Integrated Radiation and Nuclear Science, Kyoto University in 2018

Abstract

The homochirality of the L-amino acids is fundamental for the development and maintenance of life. Therefore, in the past D-amino acids were considered only as unnatural molecules in life science and there has been little knowledge on the function of D-amino acids in mammals. However, these atypical amino acids were recently found in various higher organisms, including human in the form of free amino acids, peptides, and proteins. Free Dserine, D-alanine and D-aspartate may function as a synaptic modulator in the mammalian brain. In particular, D-aspartate may play a role as a novel neuronal messenger in the maturation and differentiation of the central nervous system. On the other hand, in peptides, Damino acids are well established as essential amino acids conferring biological activities on opioid peptides and neuropeptides. Consistently with their emerging biological interest and biomedical translational value, very recent improvements in analytical chemistry, which detect amino acid enantiomers at the femtomole level, demonstrated that these atypical amino acids are no longer "unnatural" molecules in living organisms.