Directed biosynthesis of the designer peptidyl nucleoside antibiotics featuring a simplified azetidine-containing moiety

Fungal and fungal-like pathogen infections pose escalating threats to the global one-health, thus underscoring the urgent need to reverse this trend by accelerating the development of novel antifungal drugs. Polyoxin (POL), a group of structurally related nucleoside antibiotics, is an eco-friendly fungicide targeting fungal cell wall biosynthesis. However, the chemical diversity and therapeutic potential of this antibiotic has remained underexplored. Here, we report the rational design of a series of POL analogs that feature a simplified azetidine-containing moiety, and we have further realized the directed biosynthesis of them using an industrial POL producer as cell factory. Notably, three analogs (POL-A X , POL-H X , and POL-K X ), featuring a l -A2CA ( l -azetidine-2-carboxylic acid) moiety, exhibit enhanced inhibitory activity against Candida albicans and even the oomycete plant pathogen Phytophthora sojae . Moreover, systematic molecular docking analyses reveal that the three POL analogs can be better accommodated to the active pocket of the chitin synthases, directly contributing to the improved inhibitory activity of the designer POL analogs. The study provides the basis for the rational access of next-generation agents targeting chitin biosynthesis.