Life is made up from biomolecules with one-handed structure. L-dominant exclusive choice of enantiomeric type in optical amino acid isomers raises important issues concerning life science. This report discusses why it is essential for life to be made up of homochiral molecule. A mechanism that selects homochiral molecules lies in enzyme stereoselectivity, and therefore the studying of it will be important to solve a problem on origin of life and an enigma of life’s birth. This report concludes there is no life without homochirality.
In general, enzymes are essential molecules for maintaining of life and are composed of various amino acids. The amino acids synthesized chemically contain both D- and L-amino acids, but enzymes contain exclusively L-amino acids in their peptide chains. This fact leed to the origin of life, and many theories were mentioned but anyway both D- and L- amino acids co-existed at the beginning of the forming of the earth. Accordingly, D-amino acids exist more than 50 milion years ago in nature, but the existence of D-amino acids have been ignored until the analytical methods for D-amino acids develope. Recently, much attention has been payed for the relationship between D-amino acid in food and their function in life.
In this work, I will describe D-amino acid in food, especially in sake, and discuss about occurrence, production mechanism, and function of D-amino acid in sake. I analyzed D- and L-amino acids contents of 141 kind of sake by combination of 3 diffenrent chiral derivertization methods for high-performance liquid chromatography. I analyzed the relationship betwee D- or L-amino acid content and taste of sake using principle component analysis. I found that D-amino acid content of sake increased when it was produced with Kimoto. The lactic acid bacteria contained Kimoto produced extracellularly D-alanine, D-aspartic acid, and D-glutamic acid. Principle component analysis revealed that D-alanine, D-aspartic acid, and D-glutamic acid in sake increased umami and total evaluation of sake. This new function of D-amino acid in food will make various functional foods and contribute to human health in daily life.