Amino Acids in Life: A Prebiotic Division of Labor.

There are more than 20 amino acids used in Biology, and their utilization is enigmatic. Here, I propose that there was a prebiotic division of labor between two subsets of amino acids. The first set is the alpha-L set, which includes all the genetically encoded amino acids. These convey heritable information. The second set is all the remaining types, which includes the D-enantiomers incorporated in non-ribosomally encoded peptides and those used in signaling. These convey proximally mediated information about the environment. This division of labor became fixed early in the evolutionary history of life on the Earth.