Ribosomally produced peptides that contain d-amino acids have been isolated from a number of vertebrate and invertebrate sources. In each case, the d-amino acids are introduced by a posttranslational modification of a parent peptide containing only amino acids of the l-configuration. The only known enzyme to catalyze such a reaction is the peptide epimerase (also known as peptide isomerase) from the venom of the funnel web ...
