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Articles by H Ashida
Total Records ( 4 ) for H Ashida
  H Ashida , A Miyake , M Kiyohara , J Wada , E Yoshida , H Kumagai , T Katayama and K. Yamamoto

Bifidobacteria are predominant bacteria present in the intestines of breast-fed infants and offer important health benefits for the host. Human milk oligosaccharides are one of the most important growth factors for bifidobacteria and are frequently fucosylated at their non-reducing termini. Previously, we identified 1,2--l-fucosidase (AfcA) belonging to the novel glycoside hydrolase (GH) family 95, from Bifidobacterium bifidum JCM1254 (Katayama T, Sakuma A, Kimura T, Makimura Y, Hiratake J, Sakata K, Yamanoi T, Kumagai H, Yamamoto K. 2004. Molecular cloning and characterization of Bifidobacterium bifidum 1,2--l-fucosidase (AfcA), a novel inverting glycosidase (glycoside hydrolase family 95). J Bacteriol. 186:4885–4893). Here, we identified a gene encoding a novel 1,3–1,4--l-fucosidase from the same strain and termed it afcB. The afcB gene encodes a 1493-amino acid polypeptide containing an N-terminal signal sequence, a GH29 -l-fucosidase domain, a carbohydrate binding module (CBM) 32 domain, a found-in-various-architectures (FIVAR) domain and a C-terminal transmembrane region, in this order. The recombinant enzyme was expressed in Escherichia coli and was characterized. The enzyme specifically released 1,3- and 1,4-linked fucosyl residues from 3-fucosyllactose, various Lewis blood group substances (a, b, x, and y types), and lacto-N-fucopentaose II and III. However, the enzyme did not act on glycoconjugates containing 1,2-fucosyl residue or on synthetic -fucoside (p-nitrophenyl--l-fucoside). The afcA and afcB genes were introduced into the B. longum 105-A strain, which has no intrinsic -l-fucosidase. The transformant carrying afcA could utilize 2'-fucosyllactose as the sole carbon source, whereas that carrying afcB was able to utilize 3-fucosyllactose and lacto-N-fucopentaose II. We suggest that AfcA and AfcB play essential roles in degrading 1,2- and 1,3/4-fucosylated milk oligosaccharides, respectively, and also glycoconjugates, in the gastrointestinal tracts.

  Y Tani , T Funatsu , H Ashida , M Ito , S Itonori , M Sugita and K. Yamamoto

Hirsutella rhossiliensis, a nematophagous fungus belonging to the Ascomycota, is resistant to aureobasidin A (AbA). In this fungus, the biosynthetic pathway leading to mannosylinositolphosphoceramides, which is inhibited by AbA, was not detected. Instead, this fungus contains neutral complex glycosphingolipids (GSLs) and monoglycosylceramides. Except for monoglycosylceramides, neutral GSLs share a neogala-series core structure, Galβ1–6Galβ1-Cer. Among the GSLs of H. rhossiliensis, three novel GSLs with terminal Man and Glc residues on the sugar chain were elucidated. We analyzed GSL structure using compositional sugar, fatty acid, and sphingoid analyses, methylation analysis, matrix-assisted laser desorption ionization time-of-flight/mass spectrometry (MALDI-TOF MS), and 1H nuclear magnetic resonance spectroscopy (NMR). The following structures were determined: Man1–3Galβ1–6Galβ1–6Galβ1-Cer; Glc1–2Galβ1–6Galβ1–6Galβ1-Cer; and Man1–3Galβ1–6(Glc1–4)Galβ1–6Galβ1-Cer. In the ceramides, the fatty acids were predominantly saturated h24:0-acids and the sphingoids were predominately t18:0- or t18:1-sphingoids. In contrast, the ceramides of Glcβ1-Cer contained d18:2- and d19:2-sphingoids. These findings indicate the presence of a novel biosynthetic pathway of neogala-series GSLs in fungi.

  M Miwa , T Horimoto , M Kiyohara , T Katayama , M Kitaoka , H Ashida and K. Yamamoto

Bifidobacteria are predominant in the intestines of breast-fed infants and offer health benefits to the host. Human milk oligosaccharides (HMOs) are considered to be one of the most important growth factors for intestinal bifidobacteria. HMOs contain two major structures of core tetrasaccharide: lacto-N-tetraose (Galβ1-3GlcNAcβ1-3Galβ1-4Glc; type 1 chain) and lacto-N-neotetraose (Galβ1-4GlcNAcβ1-3Galβ1-4Glc; type 2 chain). We previously identified the unique metabolic pathway for lacto-N-tetraose in Bifidobacterium bifidum. Here, we clarified the degradation pathway for lacto-N-neotetraose in the same bifidobacteria. We cloned one β-galactosidase (BbgIII) and two β-N-acetylhexosaminidases (BbhI and BbhII), all of which are extracellular membrane-bound enzymes. The recombinant BbgIII hydrolyzed lacto-N-neotetraose into Gal and lacto-N-triose II, and furthermore the recombinant BbhI, but not BbhII, catalyzed the hydrolysis of lacto-N-triose II to GlcNAc and lactose. Since BbgIII and BbhI were highly specific for lacto-N-neotetraose and lacto-N-triose II, respectively, they may play essential roles in degrading the type 2 oligosaccharides in HMOs.

  R Suzuki , T Katayama , M Kitaoka , H Kumagai , T Wakagi , H Shoun , H Ashida , K Yamamoto and S. Fushinobu

Endo--N-acetylgalactosaminidase (endo--GalNAc-ase), a member of the glycoside hydrolase (GH) family 101, hydrolyses the O-glycosidic bonds in mucin-type O-glycan between -GalNAc and Ser/Thr. Endo--GalNAc-ase from Bifidobacterium longum JCM1217 (EngBF) is highly specific for the core 1-type O-glycan to release the disaccharide Galβ1-3GalNAc (GNB), whereas endo--GalNAc-ase from Clostridium perfringens (EngCP) exhibits broader substrate specificity. We determined the crystal structure of EngBF at 2.0 Å resolution and performed automated docking analysis to investigate possible binding modes of GNB. Mutational analysis revealed important residues for substrate binding, and two Trp residues (Trp748 and Trp750) appeared to form stacking interactions with the β-faces of sugar rings of GNB by substrate-induced fit. The difference in substrate specificities between EngBF and EngCP is attributed to the variations in amino acid sequences in the regions forming the substrate-binding pocket. Our results provide a structural basis for substrate recognition by GH101 endo--GalNAc-ases and will help structure-based engineering of these enzymes to produce various kinds of neo-glycoconjugates.

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