Biotransformation of Ginsenoside Rb1 to Ginsenoside F2 by Recombinant β-glucosidase from Rat Intestinal Enterococcus gallinarum

Panax ginseng is used as a traditional medicine and functional food in several Asian countries. Intestinal bacteria play an important role in the metabolism of components and the production of bioactive metabolites following oral consumption of P. ginseng. We researched the genetic and biochemical properties of the gene encoding beta-glucosidase of rat intestinal bacteria that carries out the hydrolytic metabolic reactions. We isolated the ginsenoside-transforming Enterococcus gallinarum GM2 from rat colonic contents. After cloning the GH family 3 domain protein beta-glucosidase gene (Bgy3) from E. gallinarum, we expressed and purified recombinant Bgy3 protein and then characterized it. We used LC-MS/MS to determine the metabolic profile of ginsenoside Rbl generated by Bgy3. At pH 7.0 and 40 degrees C, Bgy3 selectively removed the outer sugars of C-20 and C-3, and it produced ginsenoside F2 from ginsenoside Rb1, with a corresponding molar conversion yield of 45%. Bgy3 was found to hydrolyze the ginsenoside Rb1 according to the following pathways: Rb1 -> gypenoside XVII -> F2, or Rb1 -> Rd -> F2. Bgy3 functions in the metabolism of ginsenoside Rb1, effectively converting it into ginsenoside F2. This study clearly elucidated the relationship between intestinal bacteria and the metabolism of ginsenoside.