Motomitsu Kitaoka

National Food Research Institute, Ibaragi, Ōsaka, Japan

Are you Motomitsu Kitaoka?

Claim your profile

Publications (150)405.18 Total impact

  • Yuan Liu, Mamoru Nishimoto, Motomitsu Kitaoka
    [Show abstract] [Hide abstract]
    ABSTRACT: Three sugar 1-phosphates that are donor substrates for phosphorylases were produced at the gram scale from phosphoenolpyruvic acid and the corresponding sugars by the combined action of pyruvate kinase and the corresponding anomeric kinases in good yields. These sugar 1-phosphates were purified through two electrodialysis steps. α-d-Galactose 1-phosphate was finally isolated as crystals of dipotassium salts. α-d-Mannose 1-phosphate and 2-acetamido-2-deoxy-α-d-glucose 1-phosphate were isolated as crystals of bis(cyclohexylammonium) salts.
    Carbohydrate Research 10/2014; · 1.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The Bifidobacterium genus harbours several health promoting members of the gut microbiota. Bifidobacteria display metabolic specialization by preferentially utilizing dietary or host derived β-galactosides. This study investigates the biochemistry and structure of a glycoside hydrolase family 42 (GH42) β-galactosidase from the probiotic Bifidobacterium animalis subsp. lactis Bl-04 (BlGal42A). BlGal42A displays a preference for undecorated β1-6 and β1-3 linked galactosides and populates a phylogenetic cluster with close bifidobacterial homologues implicated in the utilization of N-acetyl substituted β1-3 galactosides from human milk and mucin. A long loop containing an invariant tryptophan in GH42, proposed to bind substrate at subsite +1, is identified here as specificity signature within this clade of bifidobacterial enzymes. Galactose binding at the subsite −1 of the active site induced conformational changes resulting in an extra polar interaction and the ordering of a flexible loop that narrows the active site. The amino-acid sequence of this loop provides an additional specificity signature within this GH42 clade. The phylogenetic relatedness of enzymes targeting β1-6 and β1-3 galactosides likely reflects structural differences between these substrates and β1-4 galactosides, containing an axial galactosidic bond. These data advance our molecular understanding of the evolution of sub-specificities that support metabolic specialization in the gut niche.
    Molecular Microbiology 10/2014; · 5.03 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 2-O-α-Glucosylglycerol phosphorylase (GGP) from Bacillus selenitireducens catalyzes both the reversible phosphorolysis of 2-O-α-glucosylglycerol (GG) and the hydrolysis of β-D-glucose 1-phosphate (βGlc1P). GGP belongs to the glycoside hydrolase (GH) family 65 and can efficiently and specifically produce GG. However, its structural basis has remained unclear. In this study, the crystal structures of GGP complexed with glucose and with the glucose analogue isofagomine and glycerol were determined. Subsite -1 of GGP is similar to those of other GH65 enzymes, maltose phosphorylase and kojibiose phosphorylase, whereas subsite +1 is largely different and is well designed for GG recognition. An automated docking analysis was performed to complement these crystal structures, βGlc1P being docked at an appropriate position. To investigate the importance of residues at subsite +1 in the bifunctionality of GGP, we constructed mutants at these residues. Y327F and K587A did not show detectable activities for either reverse phosphorolysis or βGlc1P hydrolysis. Y572F also showed significantly reduced activities for both of these reactions. In contrast, W381F showed significantly reduced reverse phosphorolytic activity but retained βGlc1P hydrolysis. The mode of substrate recognition and the reaction mechanisms of GGP were proposed based on these analyses. Specifically, an extensive hydrogen bond network formed by Tyr-327, Tyr-572, Lys-587, and water molecules contributes to fixing the acceptor molecule in both reverse phosphorolysis (glycerol) and βGlc1P hydrolysis (water) for a glycosyl transfer reaction. This study will contribute to the development of a large-scale production system of GG by facilitating the rational engineering of GGP.
    Journal of Biological Chemistry 05/2014; · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 4-O-β-d-Mannosyl-d-glucose phosphorylase (MGP), found in anaerobes, converts 4-O-β-d-mannosyl-d-glucose (Man-Glc) to α-d-mannosyl phosphate and d-glucose. It participates in mannan metabolism with cellobiose 2-epimerase (CE), which converts β-1,4-mannobiose to Man-Glc. A putative MGP gene is present in the genome of the thermophilic aerobe Rhodothermus marinus (Rm) upstream of the gene encoding CE. Konjac glucomannan enhanced production by R. marinus of MGP, CE, and extracellular mannan endo-1,4-β-mannosidase. Recombinant RmMGP catalyzed the phosphorolysis of Man-Glc through a sequential bi–bi mechanism involving ternary complex formation. Its molecular masses were 45 and 222 kDa under denaturing and nondenaturing conditions, respectively. Its pH and temperature optima were 6.5 and 75 °C, and it was stable between pH 5.5–8.3 and below 80 °C. In the reverse reaction, RmMGP had higher acceptor preferences for 6-deoxy-d-glucose and d-xylose than R. albus NE1 MGP. In contrast to R. albus NE1 MGP, RmMGP utilized methyl β-d-glucoside and 1,5-anhydro-d-glucitol as acceptor substrates.
    Bioscience Biotechnology and Biochemistry 04/2014; 78(2):263-270. · 1.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We characterized recombinant Lin1839 protein (Lin1839r) belonging to glycoside hydrolase family 94 from Listeria innocua. Lin1839r catalyzed the synthesis of a series of 1,2-β-oligoglucans (Sopn: n denotes degree of polymerization) using sophorose (Sop2) as the acceptor and α-d-glucose 1-phosphate (Glc1P) as the donor. Lin1839r recognized glucose as a very weak acceptor substrate to form polymeric 1,2-β-glucan. The degree of polymerization of the 1,2-β-glucan gradually decreased with long-term incubation to generate a series of Sopns. Kinetic analysis of the phosphorolytic reaction towards sophorotriose revealed that Lin1839r followed a sequential Bi Bi mechanism. The kinetic parameters of the phosphorolysis of sophorotetraose and sophoropentaose were similar to those of sophorotriose, although the enzyme did not exhibit significant phosphorolytic activity on Sop2. These results indicate that the Lin1839 protein is a novel inverting phosphorylase that catalyzes reversible phosphorolysis of 1,2-β-glucan with a degree of polymerization of ≥3. We propose 1,2-β-oligoglucan: phosphate α-glucosyltransferase as the systematic name and 1,2-β-oligoglucan phosphorylase as the short name for this Lin1839 protein.
    PLoS ONE 03/2014; 9(3):e92353. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The glycoside hydrolase family (GH) 65 is a family of inverting phosphorylases that act on α-glucosides. A GH65 protein (Bsel_2816) from Bacillus selenitireducens MLS10 exhibited inorganic phosphate (Pi)-dependent hydrolysis of kojibiose at the rate of 0.43 s(-1). No carbohydrate acted as acceptor for the reverse phosphorolysis using β-d-glucose 1-phosphate (βGlc1P) as donor. During the search for a suitable acceptor, we found that Bsel_2816 possessed hydrolytic activity on βGlc1P with a k cat of 2.8 s(-1); moreover, such significant hydrolytic activity on sugar 1-phosphate had not been reported for any inverting phosphorylase. The H2 (18)O incorporation experiment and the anomeric analysis during the hydrolysis of βGlc1P revealed that the hydrolysis was due to the glucosyl-transferring reaction to a water molecule and not a phosphatase-type reaction. Glycerol was found to be the best acceptor to generate 2-O-α-d-glucosylglycerol (GG) at the rate of 180 s(-1). Bsel_2816 phosphorolyzed GG through sequential Bi-Bi mechanism with a k cat of 95 s(-1). We propose 2-O-α-d-glucopyranosylglycerol: phosphate β-d-glucosyltransferase as the systematic name and 2-O-α-d-glucosylglycerol phosphorylase as the short name for Bsel_2816. This is the first report describing a phosphorylase that utilizes polyols, and not carbohydrates, as suitable acceptor substrates.
    PLoS ONE 01/2014; 9(1):e86548. · 3.53 Impact Factor
  • Ryota Fujii, Motomitsu Kitaoka, Kiyoshi Hayashi
    [Show abstract] [Hide abstract]
    ABSTRACT: We describe a simple and easy protocol to introduce random mutations into plasmid DNA: error-prone rolling circle amplification. A template plasmid is amplified via rolling circle amplification with decreased fidelity in the presence of MnCl2 and is used to transform a host strain resulting in a mutant library with several random point mutations per kilobase through the entire plasmid. The primary advantage of this method is its simplicity. This protocol does not require the design of specific primers or thermal cycling. The reaction mixture can be used for direct transformation of a host strain. This method allows rapid preparation of randomly mutated plasmid libraries, enabling wider application of random mutagenesis.
    Methods in Molecular Biology 01/2014; 1179:23-9. · 1.29 Impact Factor
  • Ryota Fujii, Motomitsu Kitaoka, Kiyoshi Hayashi
    [Show abstract] [Hide abstract]
    ABSTRACT: Although proteins can be artificially improved by random insertion and deletion mutagenesis methods, these procedures are technically difficult. Here we describe a simple method called random insertional-deletional strand exchange mutagenesis (RAISE). This method is based on gene shuffling and can be used to introduce a wide variety of insertions, deletions, and substitutions. RAISE involves three steps: DNA fragmentation, attachment of a random short sequence, and reconstruction. This yields unique mutants and can be a powerful technique for protein engineering.
    Methods in Molecular Biology 01/2014; 1179:151-8. · 1.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We characterized Teth514_1788 and Teth514_1789, belonging to glycoside hydrolase family 130, from Thermoanaerobacter sp. X-514. These two enzymes catalyzed the synthesis of 1,2-β-oligomannan using β-1,2-mannobiose and d-mannose as the optimal acceptors, respectively, in the presence of the donor α-d-mannose 1-phosphate. Kinetic analysis of the phosphorolytic reaction toward 1,2-β-oligomannan revealed that these enzymes followed a typical sequential Bi Bi mechanism. The kinetic parameters of the phosphorolysis of 1,2-β-oligomannan indicate that Teth514_1788 and Teth514_1789 prefer 1,2-β-oligomannans containing a DP ≥3 and β-1,2-Man2, respectively. These results indicate that the two enzymes are novel inverting phosphorylases that exhibit distinct chain-length specificities toward 1,2-β-oligomannan. Here, we propose 1,2-β-oligomannan:phosphate α-d-mannosyltransferase as the systematic name and 1,2-β-oligomannan phosphorylase as the short name for Teth514_1788 and β-1,2-mannobiose:phosphate α-d-mannosyltransferase as the systematic name and β-1,2-mannobiose phosphorylase as the short name for Teth514_1789.
    PLoS ONE 01/2014; 9(12):e114882. · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In-vitro synthesis of (1→3)-β-D-glucan was performed using laminaribiose phosphorylase obtained by an extraction of Euglena gracilis with sucrose phosphorylase. The synthetic product was a linear (1→3)-β-D-glucan with a narrow distribution of degree of polymerization (DP) centered on DP=30. X-ray diffraction and electron microscopy revealed that the glucan molecules obtained were self-organized as highly crystalline hexagonal lamellae. This synthetic product has quite high structural homogeneity at every level from primary to higher-order structure, which is a great advantage for the detailed analyses of physiological functions of (1→3)-β-D-glucan.
    International journal of biological macromolecules 12/2013; · 2.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Glycoside hydrolase family 42 (GH42) includes β-galactosidases catalyzing the release of galactose from the non-reducing end of different β-D-galactosides. Health-promoting probiotic bifidobacteria, which are important members of the human gastrointestinal tract microbiota, produce GH42 enzymes enabling utilization of β-galactosides exerting prebiotic effects. However, insight into the specificity of individual GH42 enzymes with respect to substrate monosaccharide composition, glycosidic linkage and degree of polymerization is lagging. Kinetic analysis of natural and synthetic substrates resembling various milk and plant galactooligosaccharides, distinguishes the three GH42 members, Bga42A, Bga42B, and Bga42C, encoded by the probiotic Bifidobacterium longum subsp. infantis ATCC 15697, and revealed the glycosyl residue at subsite +1 and its linkage to the terminal galactose at subsite-1 to be key specificity determinants. Bga42A thus prefers the β1-3-galactosidic linkage from human milk and other β1-3- and β1-6-galactosides with glucose or galactose situated at subsite +1. By contrast Bga42B very efficiently hydrolyses 4-galactosyllactose (Galβ1-4Galβ1-4Glc) as well as 4-galactobiose (Galβ1-4Gal) and 4-galactotriose (Galβ1-4Galβ1-4Gal). The specificity of Bga42C resembles that of Bga42B, but the activity was one order of magnitude lower. Based on enzyme kinetics, gene organization and phylogenetic analyses Bga42C is proposed to act in the metabolism of arabinogalactan-derived oligosaccharides. The distinct kinetic signatures of the three GH42 enzymes correlate to unique sequence motifs denoting specific clades in a GH42 phylogenetic tree providing novel insight into GH42 subspecificities. Overall the data illustrate the metabolic adaptation of bifidobacteria to the β-galactoside rich gut niche and emphasize the importance and diversity of β-galactoside metabolism in probiotic bifidobacteria.
    Glycobiology 11/2013; · 3.75 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Galacto-N-biose/lacto-N-biose I phosphorylase (GLNBP) is the key enzyme in the enzymatic production of lacto-N-biose I. For the purpose of industrial use, we improved the thermostability of GLNBP by evolutionary engineering in which five substitutions in the amino acid sequence were selected from a random mutagenesis GLNBP library constructed using error-prone polymerase chain reaction. Among them, C236Y and D576V mutants showed considerably improved thermostability. Structural analysis of C236Y revealed that the hydroxyl group of Tyr236 forms a hydrogen bond with the carboxyl group of E319. The C236Y and D576V mutations together contributed to the thermostability. The C236Y/D576V mutant exhibited 20°C higher thermostability than the wild type.
    Protein Engineering Design and Selection 09/2013; · 2.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A novel phosphorylase was characterized as new member of glycoside hydrolase family 94 from the cellulolytic bacterium Xanthomonas campestris and the fungus Neurospora crassa. The enzyme catalyzed reversible phosphorolysis of cellobionic acid. We propose 4-O-β-d-glucopyranosyl-d-gluconic acid: phosphate α-d-glucosyltransferase as the systematic name and cellobionic acid phosphorylase as the short names for the novel enzyme. Several cellulolytic fungi of the phylum Ascomycota also possess homologous proteins. We, therefore, suggest that the enzyme plays a crucial role in cellulose degradation where cellobionic acid as oxidized cellulolytic product is converted into α-d-glucose 1-phosphate and d-gluconic acid to enter glycolysis and the pentose phosphate pathway, respectively.
    FEBS letters 09/2013; · 3.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We discovered a potassium ion-dependent trehalose phosphorylase (Bsel_1207) belonging to glycoside hydrolase family 65 from halophilic Bacillus selenitireducens MLS10. Under high potassium ion concentrations, the recombinant Bsel_1207 produced in Escherichia coli existed as an active dimeric form that catalyzed the reversible phosphorolysis of trehalose in a typical sequential bi bi mechanism releasing β-d-glucose 1-phosphate and d-glucose. Decreasing potassium ion concentrations significantly reduced thermal and pH stabilities, leading to formation of inactive monomeric Bsel_1207.
    FEBS letters 09/2013; · 3.54 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A gene cluster involved in N-glycan metabolism was identified in the genome of B. thetaiotaomicron VPI-5482. This gene cluster encodes a major facilitator superfamily transporter, a starch utilization system-like transporter consisting of a TonB-dependent oligosaccharide transporter and an outer membrane lipoprotein, 4 glycoside hydrolases (α-mannosidase, β-N-acetylhexosaminidase, exo-α-sialidase, and endo-β-N-acetylglucosaminidase), and a phosphorylase (BT1033) with unknown function. It was demonstrated that BT1033 catalyzed the reversible phosphorolysis of β-1,4-D-mannosyl-N-acetyl-D-glucosamine in a typical sequential bi-bi mechanism. These results indicate that BT1033 plays a crucial role as a key enzyme in the N-glycan catabolism where β-1,4-D-mannosyl-N-acetyl-D-glucosamine is liberated from N-glycans by sequential glycoside hydrolase-catalyzed reactions, transported into the cell, and intracellularly converted into α-D-mannose 1-phosphate and N-acetyl-D-glucosamine. In addition, intestinal anaerobic bacteria such as B. fragilis, B. helcogenes, B. salanitronis, B. vulgatus, Prevotella denticola, P. dentalis, P. melaninogenica, Parabacteroides distasonis, and Alistipes finegoldii were also suggested to possess the similar metabolic pathway for N-glycans. A notable feature of the new metabolic pathway for N-glycans is the more efficient use of ATP-stored energy, in comparison with the conventional pathway where β-mannosidase and ATP-dependent hexokinase participate, because it is possible to directly phosphorylate the D-mannose residue of β-1,4-D-mannosyl-N-acetyl-D-glucosamine to enter glycolysis. This is the first report of a metabolic pathway for N-glycans that includes a phosphorylase. We propose 4-O-β-D-mannopyranosyl-N-acetyl-D-glucosamine: phosphate α-D-mannosyltransferase as the systematic name and β-1,4-D-mannosyl-N-acetyl-D-glucosamine phosphorylase as the short name for BT1033.
    Journal of Biological Chemistry 08/2013; 288(38). · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Infant-gut associated bifidobacteria possess species-specific enzymatic sets to assimilate human milk oligosaccharides (HMOs), and lacto-N-biosidase (LNBase) is a key enzyme that degrades lacto-N-tetraose (LNT, Galβ1-3GlcNAcβ1-3Galβ1-4Glc), the main component of HMOs, to lacto-N-biose I (Galβ1-3GlcNAc) and lactose. We have previously identified LNBase activity in Bifidobacterium bifidum and some strains of B. longum subsp. longum (B. longum). Subsequently, we isolated a glycoside hydrolase family 20 (GH20) LNBase from B. bifidum; however, the genome of the LNBase(+)-strain of B. longum contains no GH20 LNBase homolog. Here, we reveal that locus_tags BLLJ_1505 and BLLJ_1506 constitute LNBase from B. longum JCM1217. The gene products, designated LnbX and LnbY, respectively, showed no sequence similarity to previously characterized proteins. The purified enzyme, which consisted of LnbX only, hydrolyzed via a retaining mechanism the GlcNAcβ1-3Gal linkage in LNT, lacto-N-fucopentaose I (Fucα1-2Galβ1-3GlcNAcβ1-3Galβ1-4Glc), and sialyllacto-N-tetraose a (Neu5Acα2-3Galβ1-3GlcNAcβ1-3Galβ1-4Gal); the latter two are not hydrolyzed by GH20 LNBase. Among the chromogenic substrates examined, the enzyme acted on p-nitrophenyl (pNP)-β-lacto-N-bioside I (Galβ1-3GlcNAcβ-pNP) and GalNAcβ1-3GlcNAcβ-pNP. GalNAcβ1-3GlcNAcβ-linkage has been found in O-mannosyl glycans of α-dystroglycan. Therefore, the enzyme may serve as a new tool for examining glycan structures. In vitro refolding experiments revealed that LnbY and metal ions (Ca2+ and Mg2+) are required for proper folding of LnbX. The LnbX and LnbY homologs have been found only in B. bifidum, B. longum, and a few gut microbes, suggesting that the proteins have evolved in specialized niches.
    Journal of Biological Chemistry 07/2013; · 4.60 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Proteins belonging to the glycoside hydrolase family 63 (GH63) are found in bacteria, archaea, and eukaryotes. Although the eukaryotic GH63 proteins have been identified as processing α-glucosidase I, the substrate specificities of the bacterial and archaeal GH63 proteins are not clear. Here, we converted a bacterial GH63 enzyme, Escherichia coli YgjK, to a glycosynthase to probe its substrate specificity. Two mutants of YgjK (E727A and D324N) were constructed, and both mutants showed glycosynthase activity. The reactions of E727A with β-D-glucosyl fluoride and monosaccharides showed that the largest amount of glycosynthase product accumulated when galactose was employed as an acceptor molecule. The crystal structure of E727A complexed with the reaction product indicated that the disaccharide bound at the active site was 2-O-α-D-glucopyranosyl-α-D-galactopyranose (Glc12Gal). A comparison of the structures of E727A-Glc12Gal and D324N-melibiose showed that there were largely two types of conformations, which were the open and closed forms. The structure of YgjK adopted the closed form when the subsite -1 was occupied by glucose. These results suggest that sugars containing the Glc12Gal structure are the most likely candidates for natural substrates of YgjK. This article is protected by copyright. All rights reserved.
    FEBS Journal 07/2013; · 3.99 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Phosphorylases are one group of carbohydrate active enzymes involved in the cleavage and formation of glycosidic linkages together with glycoside hydrolases and sugar nucleotide-dependent glycosyltransferases. Noticeably, the catalyzed phosphorolysis is reversible, making phosphorylases suitable catalysts for efficient synthesis of particular oligosaccharides from a donor sugar 1-phosphate and suitable carbohydrate acceptors with strict regioselectivity. Although utilization of phosphorylases for oligosaccharide synthesis has been limited because only few different enzymes are known, recently the number of reported phosphorylases has gradually increased, providing the variation making these enzymes useful tools for efficient synthesis of diverse oligosaccharides.
    Current opinion in chemical biology 02/2013; · 8.30 Impact Factor
  • Journal of Applied Glycoscience. 01/2013; 60(3):141-146.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Lacto-N-biose I (LNB) is a potential factor for the selective growth of bifidobacteria. We previously reported that the species of bifidobacteria predominant in infant intestines might use LNB. We aimed to assess the prebiotic properties of LNB in comparison to other oligosaccharides using an in vitro fermentation system. Stool samples from formula-fed infants were inoculated with media containing a sole carbon source of 1% LNB, lactulose, raffinose, galactooligosaccharide, or mannanoligosaccharides. LNB significantly increased the total bifidobacterial population similarly to other oligosaccharides, but induced a significantly higher level of Bifidobacterium bifidum in comparison to other oligosaccharides. Furthermore, significantly lower concentrations of lactic acid and significantly higher concentrations of acetic acid were produced in cultures containing LNB in comparison to cultures that contained other oligosaccharides. In conclusion, LNB might have a beneficial effect on the fecal microbiota of infants and is a potential prebiotic for application in infant foods or supplements.
    Anaerobe 12/2012; · 2.36 Impact Factor

Publication Stats

2k Citations
405.18 Total Impact Points


  • 2001–2014
    • National Food Research Institute
      Ibaragi, Ōsaka, Japan
  • 2013
    • Technical University of Denmark
      • Department of Systems Biology
      København, Capital Region, Denmark
  • 2012–2013
    • Niigata University
      • Faculty of Agriculture
      Niahi-niigata, Niigata, Japan
    • National Agriculture and Food Research Organization
      Tsukuba, Ibaraki, Japan
  • 2008–2011
    • Ishikawa Prefectural University
      Ноноичи, Ishikawa, Japan
    • Kinki University
      Ōsaka, Ōsaka, Japan
    • Mie University
      • Graduate School of Bioresources
      Tsu-shi, Mie-ken, Japan
  • 2010
    • Kyoto University
      • Graduate School of Biostudies
      Kyoto, Kyoto-fu, Japan
  • 2009
    • Morinaga Milk Industry Co., Ltd.
      Edo, Tōkyō, Japan
  • 2004–2009
    • The University of Tokyo
      • • Faculty and Graduate School of Agriculture and Life Sceince
      • • Department of Biotechnology
      Tokyo, Tokyo-to, Japan
  • 2000
    • Agriculture, Forestry and Fisheries Research Council
      Tsukuba, Ibaraki, Japan
  • 1998–1999
    • Iowa State University
      Ames, Iowa, United States