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Articles by M Kiyohara
Total Records ( 3 ) for M Kiyohara
  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.

  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.

  M Kiyohara , K Sakaguchi , K Yamaguchi , T Araki and M. Ito
 

β-1,3-Xylanase from Vibrio sp. strain AX-4 (XYL4) is a modular enzyme composed of an N-terminal catalytic module belonging to glycoside hydrolase family 26 and two putative carbohydrate-binding modules (CBMs) belonging to family 31 in the C-terminal region. To investigate the functions of these three modules, five deletion mutants lacking individual modules were constructed. The binding assay of these mutants showed that a repeating unit of the CBM was a non-catalytic β-1,3-xylan-binding module, while the catalytic module per se was not likely to contribute to the binding activity when insoluble β-1,3-xylan was used for the assay. The repeating CBMs were found to specifically bind to insoluble β-1,3-xylan, but not to β-1,4-xylan, Avicel, β-1,4-mannan, curdlan, chitin or soluble glycol-β-1,3-xylan. Both the enzyme and the binding activities for insoluble β-1,3-xylan but not soluble glycol-β-1,3-xylan were enhanced by NaCl in a concentration-dependent manner, indicating that the CBMs of XYL4 bound to β-1,3-xylan through hydrophobic interaction. This property of the CBMs was successfully applied to the purification of a recombinant XYL4 from the cell extracts of Escherichia coli transformed with the xyl4 gene and the detection of β-1,3-xylan-binding proteins including β-1,3-xylanase from the extract of a turban shell, Turbo cornutus.

 
 
 
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