In vitro protein synthesis using D-amino acids and its evolutionary significance

The in vitro incorporations of D-Trp or -Ala into peptides were investigated using a crude system. Although none of aminoacylation to the former was observed under the present condition, the latter was utilized for peptide synthesis at the same rate as the opposite enantiomer. The results of analyzing the peptides showed that the peptides, which were synthesized with either D-, L- or DL-Ala as the substrate, were composed of mostly similar molecular size. The study of incorporations of radioisotopes (14C-D- and 3H-L-Ala) into peptides also indicated that D-Ala was by no means inferior to L-Ala for the substrate. Basing upon the present experiment, the evolutionary significance for utilizing D-amino acids is discussed.