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The Experts below are selected from a list of 168 Experts worldwide ranked by ideXlab platform

Motomitsu Kitaoka - One of the best experts on this subject based on the ideXlab platform.

Peng George Wang - One of the best experts on this subject based on the ideXlab platform.

Hayden Thompson - One of the best experts on this subject based on the ideXlab platform.

Mamoru Nishimoto - One of the best experts on this subject based on the ideXlab platform.

  • Open–close structural change upon ligand binding and two magnesium ions required for the catalysis of N-Acetylhexosamine 1-kinase
    Biochimica et biophysica acta, 2015
    Co-Authors: Mayo Sato, Mamoru Nishimoto, Motomitsu Kitaoka, Takatoshi Arakawa, Young-woo Nam, Shinya Fushinobu

    Infant gut-associated bifidobacteria possess a metabolic pathway to utilize lacto-N-biose (Gal-β1,3-GlcNAc) and galacto-N-biose (Gal-β1,3-GalNAc) from human milk and glycoconjugates specifically. In this pathway, N-Acetylhexosamine 1-kinase (NahK) catalyzes the phosphorylation of GlcNAc or GalNAc at the anomeric C1 position with ATP. Crystal structures of NahK have only been determined in the closed state. In this study, we determined open state structures of NahK in three different forms (apo, ADP complex, and ATP complex). A comparison of the open and closed state structures revealed an induced fit structural change defined by two rigid domains. ATP binds to the small N-terminal domain, and binding of the N-Acetylhexosamine substrate to the large C-terminal domain induces a closing conformational change with a rotation angle of 16°. In the nucleotide binding site, two magnesium ions bridging the α-γ and β-γ phosphates were identified. A mutational analysis indicated that a residue coordinating both of the two magnesium ions (Asp228) is essential for catalysis. The involvement of two magnesium ions in the catalytic machinery is structurally similar to the catalytic structures of protein kinases and aminoglycoside phosphotransferases, but distinct from the structures of other anomeric kinases or sugar 6-kinases. These findings help to elucidate the possible evolutionary adaptation of substrate specificities and induced fit mechanism.

  • Identification of amino acid residues that determine the substrate preference of 1,3-β-galactosyl-N-Acetylhexosamine phosphorylase
    Journal of Molecular Catalysis B: Enzymatic, 2012
    Co-Authors: Mamoru Nishimoto, Masahiro Nakajima, Shinya Fushinobu, Masafumi Hidaka, Motomitsu Kitaoka

    Abstract Three amino acid residues of 1,3-β-galactosyl- N -acetylhexosamine phosphorylase (GalHexNAcP) were assigned as the determinants of substrate preference for galacto- N -biose (GNB) and lacto- N -biose I (LNB) based on the three-dimensional structure of the protein. Mutants of GalHexNAcP from Bifidobacterium longum , which acts similarly on both GNB and LNB, were constructed and characterized. V162T mutation led to an increase in the selectivity on GNB. P161S and S336A mutations independently enhanced the selectivity on LNB. The alignment of amino acid sequences suggests that the activities of most homologous sequences are predictable by comparing the corresponding three residues.

  • Characterization of β-1,3-galactosyl-N-Acetylhexosamine phosphorylase from Propionibacterium acnes
    Applied Microbiology and Biotechnology, 2009
    Co-Authors: Masahiro Nakajima, Mamoru Nishimoto, Motomitsu Kitaoka

    Homologs of the β-1,3-galactosyl- N -acetylhexosamine phosphorylase (GalHexNAcP) gene ( gnpA ) were cloned from the genomic DNA of Propionibacterium acnes JCM6425 and P. acnes JCM6473, showing 99.9% and 97.9% nucleotide sequence identity, respectively, with the ppa0083 gene from the genome-sequenced P. acnes KPA171202. No gnpA gene was detected in the genomic DNA of type strain P. acnes ATCC25746. The recombinant enzyme from P. acnes JCM6425 (GnpA) showed approximately 70 times higher specific activity of phosphorolysis on galacto- N -biose (Galβ1→3GalNAc, GNB) than that on lacto- N -biose I (Galβ1→3GlcNAc). K _m value for GnpA on GNB was high, but GnpA did not exhibit activity on any derivatives of GNB examined. These results indicate that GnpA is GalHexNAcP which should be classified as galacto- N -biose phosphorylase. The large k _cat value of GnpA on GalNAc suggests that GnpA would be a useful catalyst for the synthesis of GNB.

  • identification of n acetylhexosamine 1 kinase in the complete lacto n biose i galacto n biose metabolic pathway in bifidobacterium longum
    Applied and Environmental Microbiology, 2007
    Co-Authors: Mamoru Nishimoto, Motomitsu Kitaoka

    We have determined the functions of the enzymes encoded by the lnpB, lnpC, and lnpD genes, located downstream of the lacto-N-biose phosphorylase gene (lnpA), in Bifidobacterium longum JCM1217. The lnpB gene encodes a novel kinase, N-Acetylhexosamine 1-kinase, which produces N-Acetylhexosamine 1-phosphate; the lnpC gene encodes UDP-glucose hexose 1-phosphate uridylyltransferase, which is also active on N-Acetylhexosamine 1-phosphate; and the lnpD gene encodes a UDP-glucose 4-epimerase, which is active on both UDP-galactose and UDP-N-acetylgalactosamine. These results suggest that the gene operon lnpABCD encodes a previously undescribed lacto-N-biose I/galacto-N-biose metabolic pathway that is involved in the intestinal colonization of bifidobacteria and that utilizes lacto-N-biose I from human milk oligosaccharides or galacto-N-biose from mucin sugars.

Wanyi Guan - One of the best experts on this subject based on the ideXlab platform.