Various mechanisms in cyclopeptide production from precursors synthesized independently of non-ribosomal peptide synthetases.

An increasing number of cyclopeptides have been discovered as products of ribosomal synthetic pathway. The biosynthetic study of these cyclopeptides has revealed interesting new mechanisms for cyclization. This review highlighted the recent discoveries in cyclization mechanisms for cyclopeptides synthesized independently of non-ribosomal peptide synthetases, including endopeptidase-catalyzed cyclization, intein-mediated cyclization, and peptide synthetase-catalyzed cyclization. This information may help to design hybrid ribosomal and non-ribosomal biosynthetic systems to produce novel cyclopeptides with various bioactivities.