Understanding how antibiotic-producing bacteria deal with highly reactive chemicals will ultimately guide therapeutic strategies to combat the increasing clinical resistance crisis. Here, we uncovered a distinctive self-defense strategy featured by a secreted oxidoreductase NapU to perform extracellularly oxidative activation and conditionally overoxidative inactivation of a matured prodrug in naphthyridinomycin (NDM) biosynthesis from Streptomyces lusitanus NRRL 8034. It was suggested that formation of NDM first involves a nonribosomal peptide synthetase assembly line to generate a prodrug. After exclusion and prodrug maturation, we identified a pharmacophore-inactivated intermediate, which required reactivation by NapU via oxidative C-H bond functionalization extracellularly to afford NDM. Beyond that, NapU could further oxidatively inactivate the NDM pharmacophore to avoid self-cytotoxicity if they coexist longer than necessary. This discovery represents an amalgamation of sophisticatedly temporal and spatial shielding mode conferring self-resistance in antibiotic biosynthesis from Gram-positive bacteria.
Keywords: natural product biosynthesis; secreted enzyme; self-protection; tetrahydroisoquinoline alkaloids; warhead.