Perspectives on the Origin of Biological Homochirality on Earth.

The origin of biological homochirality on Earth has been an important unresolved issue in the field of molecular evolution and many hypotheses have been proposed to explain this. The most prevailing view may be that of astrobiologists, in that a slight enantiomeric excess of L-amino acids in meteorites can account for the origin. However, the view ignores two important factors: amino acid racemization, and the evolution and continuity of biological systems on Earth. Therefore, on the basis of these two standpoints, the plausibility of the hypothesis that chiral-selective tRNA aminoacylation could have led to crucial homochiral protein biosynthesis should be emphasized. Recent molecular dynamic simulations have clearly elucidated the mechanisms of enantiomer-specific aminoacylation. These studies strengthen the possibility that the hypothesized chiral selection of amino acids in biological systems actually occurred at the molecular level. It is significant to raise the points because the topic so far has tended to be expressed unclearly and ambiguously and also handled as such owing to its very nature.