Origin of D-Amino-acids in Microbial Peptides: Rule of α-Epimerization

RECENT surveys 1–3 of the structural relationships of peptide antibiotics and other peptides of microbial origin have revealed that the biosynthesis of these compounds differs 1,2 from that of proteins and does not involve the nucleic acid based genetic code. Some contrary evidence, the isolation of a messenger-RNA for synthesis of gramicidin S , has been withdrawn 4 . Nevertheless, some common features between proteins and microbial peptides can also be recognized. Such a common feature could be that both originate from amino-acids of the L-configuration 5,6 . Indeed, we have evidence that the D-amino-acid residues are derived from L-amino-acids.