Discovery of an ene-reductase for initiating flavone and flavonol catabolism in gut bacteria

Nat Commun. 2021 Feb 4;12(1):790. doi: 10.1038/s41467-021-20974-2.


Gut microbial transformations of flavonoids, an enormous class of polyphenolic compounds abundant in plant-based diets, are closely associated with human health. However, the enzymes that initiate the gut microbial metabolism of flavones and flavonols, the two most abundant groups of flavonoids, as well as their underlying molecular mechanisms of action remain unclear. Here, we discovered a flavone reductase (FLR) from the gut bacterium, Flavonifractor plautii ATCC 49531 (originally assigned as Clostridium orbiscindens DSM 6740), which specifically catalyses the hydrogenation of the C2-C3 double bond of flavones/flavonols and initiates their metabolism as a key step. Crystal structure analysis revealed the molecular basis for the distinct catalytic property of FLR. Notably, FLR and its widespread homologues represent a class of ene-reductases that has not been previously identified. Genetic and biochemical analyses further indicated the importance of FLR in gut microbial consumption of dietary and medicinal flavonoids, providing broader insight into gut microbial xenobiotic transformations and possible guidance for personalized nutrition and medicine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / metabolism*
  • Bacterial Proteins / ultrastructure
  • Clostridiales / enzymology
  • Clostridiales / genetics
  • Crystallography, X-Ray
  • Flavones / metabolism*
  • Flavonols / metabolism*
  • Gastrointestinal Microbiome / physiology*
  • Oxidoreductases / genetics
  • Oxidoreductases / isolation & purification
  • Oxidoreductases / metabolism*
  • Oxidoreductases / ultrastructure
  • Phylogeny
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / ultrastructure


  • Bacterial Proteins
  • Flavones
  • Flavonols
  • Recombinant Proteins
  • Oxidoreductases

Supplementary concepts

  • Flavonifractor plautii