Cyclic peptide production using a macrocyclase with enhanced substrate promiscuity and relaxed recognition determinantsElectronic supplementary information (ESI) available: Experimental section, Fig. S1-S60 and Tables S1-S3. See DOI: 10.1039/c7cc05913b

Macrocyclic peptides have promising therapeutic potential but the scaling up of their chemical synthesis is challenging. The cyanobactin macrocyclase PatG mac is an efficient tool for production but is limited to substrates containing 6-11 amino acids and at least one thiazoline or proline. Here we report a new cyanobactin macrocyclase that can cyclize longer peptide substrates and those not containing proline/thiazoline and thus allows exploring a wider chemical diversity. The cyanobactin macrocyclase (OscG mac ) has high substrate promiscuity and can be used for making libraries of highly diverse cyclic peptides.