title: A family 3 glycosyl hydrolase of Dickeya dadantii 3937 is involved in the cleavage of aromatic glucosides.
abstract: Dickeya dadantii is a phytopathogenic bacterium secreting a large array of plant-cell-wall-degrading enzymes that participate in the infection and maceration of the host plant tissue. Sequencing of the D. dadantii 3937 genome predicted several genes encoding potential glycosidases. One of these genes, bgxA, encodes a protein classified in family 3 of glycosyl hydrolases. Inactivation of bgxA and the use of a gene fusion revealed that this gene is not essential for D. dadantii pathogenicity but that it is expressed during plant infection. The bgxA expression is induced in the presence of glycosidic or non-glycosidic aromatic compounds, notably ferulic acid, cinnamic acid, vanillic acid and salicin. The BgxA enzyme has a principal β-d-glucopyranosidase activity and a secondary β-d-xylopyranosidase activity (ratio 70 : 1). This enzyme activity is inhibited by different aromatic glycosides or phenolic compounds, in particular salicin, arbutin, ferulic acid and vanillic acid. Together, the induction effects and the enzyme inhibition suggest that BgxA is mostly involved in the cleavage of aromatic β-glucosides. There is evidence of functional redundancy in the D. dadantii β-glucoside assimilation pathway. In contrast to other β-glucoside assimilation systems, involving cytoplasmic phospho-β-glucosidases, the cleavage of aromatic glucosides in the periplasmic space by BgxA may avoid the release of a toxic phenolic aglycone into the cytoplasm while still allowing for catabolism of the glucose moiety.
authors.affiliation: Université de Lyon, Microbiologie Adaptation et Pathogénie, CNRS UMR5240, INSA-Lyon, Université Lyon 1, Domaine Scientifique de la Doua, Villeurbanne F-69622, France.|Université Mentouri de Constantine, 25000 Constantine, Algeria.
authors.forename: Sana
authors.initials: S
authors.lastname: Charaoui-Boukerzaza
authors.affiliation: Université de Lyon, Microbiologie Adaptation et Pathogénie, CNRS UMR5240, INSA-Lyon, Université Lyon 1, Domaine Scientifique de la Doua, Villeurbanne F-69622, France.
authors.forename: Nicole
authors.initials: N
authors.lastname: Hugouvieux-Cotte-Pattat
mesh_terms: D018651:Cichorium intybus / Q000382:microbiology; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism; D020869:Gene Expression Profiling; D050939:Gene Fusion; D055786:Gene Knockout Techniques; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism*; D018515:Plant Leaves / Q000382:microbiology; D015533:Transcriptional Activation
chemical_list: D004791:Enzyme Inhibitors; D006027:Glycosides; D006026:Glycoside Hydrolases