Possible mechanism for origin of chiral specificity during origins of life.

We have earlier (Origins of Life 10 (1980), 15-30) proposed a conformational theory for the origin of nucleic acid-directed adaptor-mediated ordered and proliferative synthesis of proteins and hence origin of life. Conjunction of L-amino acids and beta-D-ribonucleotides emerges as a natural consequence of a template fitting interaction in this theory of the origin of the genetic decoding apparatus. Here we propose an interesting new concept for the origin of chiral specificity, by showing that two autonomously developing systems of protein-synthesizing machinery, one manufacturing L-peptides (L-system) and the other, D-peptides (D-system) could have arisen and during early stages of evolution L-system could have developed a killer enzyme to destroy the D-system, causing the presently existing chiral specificity in all the evolved organisms on Earth. It would be interesting to look for such 'killer enzymes' in the present-day organisms. Of course, the existence of D-amino acid-containing antibiotics gives some credence to this theory.