Microbes produce specialized metabolites to thrive in their natural habitats. However, it is rare that a given specialized metabolite is biosynthesized via pathways with distinct intermediates and enzymes. Here, we… Click to show full abstract
Microbes produce specialized metabolites to thrive in their natural habitats. However, it is rare that a given specialized metabolite is biosynthesized via pathways with distinct intermediates and enzymes. Here, we show that the core assembly mechanism of the antibiotic indolmycin in marine gram-negative Pseudoalteromonas luteoviolacea is distinct from its counterpart in terrestrial gram-positive Streptomyces species, with a molecule that is a shunt product in the Streptomyces pathway employed as a biosynthetic substrate for a novel metal-independent N-demethylindolmycin synthase in the P. luteoviolacea pathway. To provide insight into this reaction, we solved the 1.5 Å resolution structure in complex with product and identified the active site residues. Guided by our biosynthetic insights, we then engineered the Streptomyces indolmycin producer for titer improvement. This study provides a paradigm for understanding how two unique routes to a microbial specialized metabolite can emerge from convergent biosynthetic transformations.The indolmycin biosynthetic pathway in a marine gram-negative bacterium is distinct from its counterpart in terrestrial gram-positive Streptomyces species, using a Streptomyces shunt product as a substrate for an N-demethylindolmycin synthase.
               
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