Biosynthesis of Fluorinated Aromatic Polyketides Through Directed Evolution of Fused Type III Polyketide Synthase

ABSTRACT Aromatic polyketides have gained significant attention as prominent plant‐derived polyphenol molecules in recent years owing to their multi‐faceted therapeutic potentials against a variety of diseases. However, the introduction of unique fluorine atoms into the core structure of aromatic polyketides has received limited exploration thus far. In this study, a series of new‐to‐nature fluorinated aromatic polyketides, including resveratrol, naringenin chalcone, bisnoyangonin, and benzalactone, were obtained from readily available fluoro‐tyrosines in E. coli via a multi‐enzyme cascade pathway. A series of combinational optimization strategies, including metabolic regulations, double protein fusion (4CL::III‐PKS and MatB::III‐PKS), and directed evolution of the rate‐limiting enzymes, were conducted to improve the production of fluoro‐aromatic polyketides, thus enhancing the titers to >200 mg/L from an initial ∼10 mg/L. When both sides of the phenolic hydroxyl group of 4‐coumaroyl‐CoA contain fluorine atoms, a novel catalytic pathway of STS and CHS in synthesizing methyl ketone structures is unlocked, namely the “ proximal fluorine‐induced III‐PKS catalytic truncation ”. Further post‐functionalizations by enzymatic glycosylation reaction and chemocatalytic Friedel–Crafts‐type reaction provided the corresponding fluorinated derivatives of polyphenolic natural products (piceid and arahypin).