Discovery of a Single Monooxygenase that Catalyzes Carbamate Formation and Ring Contraction in the Biosynthesis of the Legonmycins

Pyrrolizidine alkaloids (PAs) are a group of natural products with important biological activities. The discovery and characterization of the multifunctional FAD‐dependent enzyme LgnC is now described. The enzyme is shown to convert indolizidine intermediates into pyrrolizidines through an unusual ring expansion/contraction mechanism, and catalyze the biosynthesis of new bacterial PAs, the so‐called legonmycins. By genome‐driven analysis, heterologous expression, and gene inactivation, the legonmycins were also shown to originate from non‐ribosomal peptide synthetases (NRPSs). The biosynthetic origin of bacterial PAs has thus been disclosed for the first time. Enzym‐Solo: Die Legonmycine, neue bakterielle Pyrrolizidin‐Alkaloide, werden von einer nicht‐ribosomalen Peptidsynthetase produziert. Das multifunktionelle, FAD‐enthaltende Enzym LgnC katalysiert die Umsetzung der Indolizidin‐Intermediate zu Pyrrolizidinen durch Carbamatbildung gefolgt von Hydrolyse, decarboxylierender Ringkontraktion und Hydroxylierung als wichtige Stufen der Legonmycin‐Biosynthese.