Identification of a Novel Dihydrodaidzein Racemase Essential for Biosynthesis of Equol from Daidzein in Lactococcus sp. Strain 20-92

Abstract

ABSTRACT Equol is metabolized from daidzein, a soy isoflavone, by the gut microflora. In this study, we identified a novel dihydrodaidzein racemase ( l -DDRC) that is involved in equol biosynthesis in a lactic acid bacterium, Lactococcus sp. strain 20-92, and confirmed that histidine-tagged recombinant l -DDRC ( l -DDRC-His) was able to convert both the ( R )- and ( S )-enantiomers of dihydrodaidzein to the racemate. Moreover, we showed that recombinant l -DDRC-His was essential for in vitro equol production from daidzein by a recombinant enzyme mixture and that efficient in vitro equol production from daidzein was possible using at least four enzymes, including l -DDRC. We also proposed a model of the metabolic pathway from daidzein to equol in Lactococcus strain 20-92.