Chemical aspects of peptide bond isomerisation

Coplanarity of peptide bonds confers partitioning of peptide chains between two energetically preferred rotational states, cis and trans. Molecular heterogeneity is particularly pronounced when imino acids like proline form the peptide bond. These conformational substates are prone to isomer-specific biochemical recognition, delayed chain folding and biocatalysis of conformational interconversion attracting broad interest in medicinal chemistry and biotechnology. The present review discusses the structural features of peptide bond conformation in oligopeptides and proteins, and gives an overview of isomer ratios, interconversion rates, and catalysis.