title: Bifidobacterial α-galactosidase with unique carbohydrate-binding module specifically acts on blood group B antigen.
abstract: Bifidobacterium bifidum is one of the most frequently found bifidobacteria in the intestines of newborn infants. We previously reported that B. bifidum possesses unique metabolic pathways for O-linked glycans on gastrointestinal mucin (Yoshida E, Sakurama H, Kiyohara M, Nakajima M, Kitaoka M, Ashida H, Hirose J, Katayama T, Yamamoto K, Kumagai H. 2012. Bifidobacterium longum subsp. infantis uses two different β-galactosidases for selectively degrading type-1 and type-2 human milk oligosaccharides. Glycobiology. 22:361-368). The nonreducing termini of O-linked glycans on mucin are frequently covered with histo-blood group antigens. Here, we identified a gene agabb from B. bifidum JCM 1254, which encodes glycoside hydrolase (GH) family 110 α-galactosidase. AgaBb is a 1289-amino acid polypeptide containing an N-terminal signal sequence, a GH110 domain, a carbohydrate-binding module (CBM) 51 domain, a bacterial Ig-like (Big) 2 domain and a C-terminal transmembrane region, in this order. The recombinant enzyme expressed in Escherichia coli hydrolyzed α1,3-linked Gal in branched blood group B antigen [Galα1-3(Fucα1-2)Galβ1-R], but not in a linear xenotransplantation antigen (Galα1-3Galβ1-R). The enzyme also acted on group B human salivary mucin and erythrocytes. We also revealed that CBM51 specifically bound blood group B antigen using both isothermal titration calorimetry and a solid-phase binding assay, and it enhanced the affinity of the enzyme toward substrates with multivalent B antigens. We suggest that this enzyme plays an important role in degrading B antigens to acquire nutrients from mucin oligosaccharides in the gastrointestinal tracts.
authors.affiliation: Graduate School of Biostudies,  Kyoto University, Kyoto 606-8502,  Japan.
authors.forename: Takura
authors.initials: T
authors.lastname: Wakinaka
authors.forename: Masashi
authors.initials: M
authors.lastname: Kiyohara
authors.forename: Shin
authors.initials: S
authors.lastname: Kurihara
authors.forename: Akiko
authors.initials: A
authors.lastname: Hirata
authors.forename: Thida
authors.initials: T
authors.lastname: Chaiwangsri
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ohnuma
authors.forename: Tamo
authors.initials: T
authors.lastname: Fukamizo
authors.forename: Takane
authors.initials: T
authors.lastname: Katayama
authors.forename: Hisashi
authors.initials: H
authors.lastname: Ashida
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D000017:ABO Blood-Group System / Q000378:metabolism; D001644:Bifidobacterium / Q000201:enzymology*; D001789:Blood Group Antigens / Q000302:isolation & purification / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007422:Intestines / Q000382:microbiology; D008895:Milk, Human / Q000201:enzymology; D009077:Mucins / Q000737:chemistry / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000302:isolation & purification; D000519:alpha-Galactosidase / Q000235:genetics / Q000302:isolation & purification; D001616:beta-Galactosidase / Q000737:chemistry / Q000378:metabolism
chemical_list: D000017:ABO Blood-Group System; D001789:Blood Group Antigens; D009077:Mucins; D011134:Polysaccharides; D011956:Receptors, Cell Surface; C055213:saccharide-binding proteins; D000519:alpha-Galactosidase; D001616:beta-Galactosidase