title: Identification and functional expression of genes encoding flavonoid O- and C-glycosidases in intestinal bacteria.
abstract: Gut bacteria play a crucial role in the metabolism of dietary flavonoids and thereby influence the bioactivity of these compounds in the host. The intestinal Lachnospiraceae strain CG19-1 and Eubacterium cellulosolvens are able to deglycosylate C- and O-coupled flavonoid glucosides. Growth of strain CG19-1 in the presence of the isoflavone C-glucoside puerarin (daidzein 8-C-glucoside) led to the induction of two proteins (DfgC, DfgD). Heterologous expression of the encoding genes (dfgC, dfgD) in Escherichia coli revealed no C-deglycosylating activity in the resulting cell extracts but cleavage of flavonoid O-glucosides such as daidzin (daidzein 7-O-glucoside). The recombinant DfgC and DfgD proteins were purified and characterized with respect to their quaternary structure, substrate and cofactor specificity. The products of the corresponding genes (dfgC, dfgD) from E. cellulosolvens also catalysed the O-deglycosylation of daidzin following their expression in E. coli. In combination with three recombinant proteins encoded by adjacent genes in E. cellulosolvens (dfgA, dfgB, dfgE), DfgC and DfgD from E. cellulosolvens catalysed the deglycosylation of the flavone C-glucosides homoorientin (luteolin 6-C-glucoside) and isovitexin (apigenin 6-C-glucoside). Even intact cells of E. coli expressing the five E. cellulosolvens genes cleaved these flavone C-glucosides and, also, flavonoid O-glucosides to the corresponding aglycones.
authors.affiliation: Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, Nuthetal, D-14558, Germany.
authors.forename: Annett
authors.initials: A
authors.lastname: Braune
authors.affiliation: Analytics Group, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, Nuthetal, D-14558, Germany.
authors.forename: Wolfram
authors.initials: W
authors.lastname: Engst
authors.affiliation: Department of Gastrointestinal Microbiology, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, Nuthetal, D-14558, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Blaut
mesh_terms: D001419:Bacteria / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007422:Intestines / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D005419:Flavonoids; D006026:Glycoside Hydrolases