From the prebiotic synthesis of α-amino acids towards a primitive translation apparatus for the synthesis of peptides

Abstract

The demonstration that ribosomal peptide synthesis is a ribozyme-catalyzed reaction does not establish that amino acids and peptides have been useless and/or missing in an RNA world. The prebiotic chemistry of amino acids and peptides thus remains an important field of investigation. We first review the literature on amino acid synthesis and then focus on the topic of peptide synthesis pathways. Most proposed pathways are examined in the context of the thermodynamic constraints on peptide bond formation and using yet unpublished evaluations of the free energy contents of activated intermediates. This analysis provides evidences in favor of an important role of α-amino acid N-carboxyanhydrides (NCAs) as activated peptide monomers and possibly as early free energy carriers owing to their ability to activate inorganic phosphate and nucleotides. Finally, the transition towards the emergence of the biochemical amino acid activation pathways involving amino acid-phosphoric acid mixed anhydrides via both ribosomal and non-ribosomal processes is analyzed from the perspective that life emerged through a coevolution linking amino acid and nucleotide chemistries.