Monobactam formation in sulfazecin by a nonribosomal peptide synthetase thioesterase

摘要

The N-sulfonated monocyclic beta-lactam ring characteristic of the monobactams confers resistance to zinc metallo-beta-lactamases and affords the most effective class to combat carbapenem-resistant enterobacteria (CRE). Here we report unprecedented nonribosomal peptide synthetase activities, wherein an assembled tripeptide is N-sulfonated in trans before direct synthesis of the beta-lactam ring in a noncanonical, cysteine-containing thioesterase domain. This means of azetidinone synthesis is distinct from the three others known in nature.