title: Glycoside hydrolase family 13 α-glucosidases encoded by Bifidobacterium breve UCC2003; A comparative analysis of function, structure and phylogeny.
abstract: Bifidobacterium breve is a noted inhabitant and one of the first colonizers of the human gastro intestinal tract (GIT). The ability of this bacterium to persist in the GIT is reflected by the abundance of carbohydrate-active enzymes that are encoded by its genome. One such family of enzymes is represented by the α-glucosidases, of which three, Agl1, Agl2 and MelD, have previously been identified and characterized in the prototype B. breve strain UCC2003. In this report, we describe an additional B. breve UCC2003-encoded α-glucosidase, along with a B. breve UCC2003-encoded α-glucosidase-like protein, designated here as Agl3 and Agl4, respectively, which together with the three previously described enzymes belong to glycoside hydrolase (GH) family 13. Agl3 was shown to exhibit hydrolytic specificity towards the α-(1→6) linkage present in palatinose; the α-(1→3) linkage present in turanose; the α-(1→4) linkages found in maltotriose and maltose; and to a lesser degree, the α-(1→2) linkage found in sucrose and kojibiose; and the α-(1→5) linkage found in leucrose. Surprisingly, based on the substrates analyzed, Agl4 did not exhibit biologically relevant α-glucosidic activity. With the presence of four functionally active GH13 α-glucosidases, B. breve UCC2003 is capable of hydrolyzing all α-glucosidic linkages that can be expected in glycan substrates in the lower GIT. This abundance of α-glucosidases provides B. breve UCC2003 with an adaptive ability and metabolic versatility befitting the transient nature of growth substrates in the GIT.
authors.affiliation: APC Microbiome Institute, University College Cork, Western Road, Cork, Ireland; School of Microbiology, University College Cork, Western Road, Cork, Ireland.
authors.forename: Emer D
authors.initials: ED
authors.lastname: Kelly
authors.affiliation: APC Microbiome Institute, University College Cork, Western Road, Cork, Ireland.
authors.forename: Francesca
authors.initials: F
authors.lastname: Bottacini
authors.affiliation: School of Microbiology, University College Cork, Western Road, Cork, Ireland.
authors.forename: John
authors.initials: J
authors.lastname: O'Callaghan
authors.affiliation: APC Microbiome Institute, University College Cork, Western Road, Cork, Ireland.
authors.forename: Mary O'Connell
authors.initials: MO
authors.lastname: Motherway
authors.affiliation: APC Microbiome Institute, University College Cork, Western Road, Cork, Ireland; School of Microbiology, University College Cork, Western Road, Cork, Ireland.
authors.forename: Kerry Joan
authors.initials: KJ
authors.lastname: O'Connell
authors.affiliation: APC Microbiome Institute, University College Cork, Western Road, Cork, Ireland; Teagasc Food Research Centre Moorepark, Fermoy, Ireland.
authors.forename: Catherine
authors.initials: C
authors.lastname: Stanton
authors.affiliation: APC Microbiome Institute, University College Cork, Western Road, Cork, Ireland; School of Microbiology, University College Cork, Western Road, Cork, Ireland. Electronic address: d.vansinderen@ucc.ie.
authors.forename: Douwe
authors.initials: D
authors.lastname: van Sinderen
mesh_terms: D001644:Bifidobacterium / Q000145:classification* / Q000201:enzymology* / Q000235:genetics*; D004187:Disaccharides / Q000378:metabolism; D010802:Phylogeny; D000520:alpha-Glucosidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D004187:Disaccharides; D000520:alpha-Glucosidases
keywords: Carbohydrate metabolism; Maltose; Palatinose; Prebiotic; Probiotic; Sucrose and/or sucrose analogs