Introduction of α-N-methylated non-proteinogenic amino acids into peptides can improve their biological activities, membrane permeability and proteolytic stability. This is commonly achieved, in nature and in the lab, by assembling pre-methylated amino acids. The more appealing route of methylating amide bonds is challenging. Biology has evolved an α-N-automethylating enzyme, OphMA, which acts on the amide bonds of peptides fused to its C-terminus. Due to the ribosomal biosynthesis of its substrate, the activity of this enzyme towards peptides with non-proteinogenic amino acids has not been addressed. An engineered OphMA, intein-mediated protein ligation and solid-phase peptide synthesis have allowed us to demonstrate the methylation of amide bonds in the context of non-natural amides. This approach may have application in the biotechnological production of therapeutic peptides.
Peptide backbone methylation is a highly desired modification. Using split intein, synthetic peptides and an engineered variant of the methylase, fOphMA2, it was possible to enzymatically methylate amide bonds involving non‐natural amino acids. This has application in the biotechnological production of therapeutic peptides.
Keywords: RiPPs; cyclic peptide; non-proteinogenic amino acids; split intein; α-N-methylation.
© 2021 The Authors. Angewandte Chemie published by Wiley-VCH GmbH.