著者

Shinya Fushinobu Masafumi Hidaka Andressa M. Hayashi Takayoshi Wakagi Hirofumi Shoun Motomitsu Kitaoka

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

vol.58, no.3, pp.91-97, 2011 (Released:2011-09-07)

参考文献数

29

被引用文献数

5 9

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Azasugars are known as potent inhibitors of glycoside hydrolases. In this study, we examined the inhibition of Cellvibrio gilvus cellobiose phosphorylase (CBP) by four azasugars (isofagomine, 1-deoxynojirimycin, castanospermine and calystegine B2) and a non-azasugar (glucono-1,5-lactone). Isofagomine strongly inhibited CBP, whereas 1-deoxynojirimycin, castanospermine, and glucono-1,5-lactone exhibited moderate or weak inhibition. Calystegine B2 did not inhibit CBP. Kinetic analysis in the presence of sulfate indicated that it is an extremely weak competitive inhibitor against phosphate. Moreover, crystal structures of CBP complexed with isofagomine or 1-deoxynojirimycin were determined, revealing molecular recognition of the glucosidase inhibitors by the phosphorolytic enzyme. These inhibitors are bound at subsite −1 and form several hydrogen bonds with the protein and anion (phosphate or sulfate). The strong inhibition by isofagomine is probably due to an electrostatic interaction between its endocyclic amino group and phosphate.

著者

Motomitsu Kitaoka

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

pp.jag.JAG-2022_0012, (Released:2022-12-17)

被引用文献数

5

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We created a Microsoft Excel file, Enzyme_Kinetics_Calculator, which includes macro programs that automatically calculates kinetic parameters for typical kinetic equations of enzymatic reactions, accompanied by their standard errors, by minimizing the residual sum of squares thereof. The [S]–v plot is automatically drawn with the theoretical lines and, similarly, the 1/[S]-1/v plot in the case of linear theoretical lines. Enzyme_Kinetics_Calculator is available as a supplementary file for this paper (see J. Appl. Glycosci. Web site).

著者

Shuntaro Machida Katsuichi Saito Mamoru Nishimoto Motomitsu Kitaoka

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

pp.jag.JAG-2021_0012, (Released:2022-02-25)

被引用文献数

1

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Lacto-N-biose I (LNB) is supposed to represent the bifidus factor in human milk oligosaccharides, and can be practically produced from sucrose and GlcNAc using four bifidobacterial enzymes, 1,3-β-galactosyl-N-acetylhexosamine phosphorylase, sucrose phosphorylase, UDP-glucose-hexose 1-phosphate uridylyltransferase, and UDP-glucose 4-epimerase, recombinantly produced by Escherichia coli. Here the production of LNB by the same enzymatic method without using genetically modified enzymes to consider the use of LNB for a food ingredient was reported. All four enzymes were produced as the intracellular enzymes of Bifidobacterium strains. The mixture of the crude extracts contained all four enzymes, with other enzymes interfering with the LNB production, namely, phosphoglucomutase, fructose 6-phosphate phosphoketolase, and glycogen phosphorylase. The first two interfering enzymes were selectively inactivated by heat treatment at 47 °C for 1 h in the presence of pancreatin, and glycogen phosphorylase was disabled by hydrolyzing its possible acceptor molecules using glucoamylase. Finally, 91 % of GlcNAc was converted into LNB in the 100-mL reaction mixture containing 300 mM GlcNAc.

著者

Kiyohiko Igarashi Satoshi Kaneko Motomitsu Kitaoka Masahiro Samejima

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

vol.67, no.2, pp.51-57, 2020-05-20 (Released:2020-05-20)

参考文献数

40

被引用文献数

2

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Cellobiose dehydrogenase (CDH) is a flavocytochrome catalyzing oxidation of the reducing end of cellobiose and cellooligosaccharides, and has a key role in the degradation of cellulosic biomass by filamentous fungi. Here, we use a lineup of glucose/xylose-mixed β-1,4-linked disaccharides and trisaccharides, enzymatically synthesized by means of the reverse reaction of cellobiose phosphorylase and cellodextrin phosphorylase, to investigate the substrate recognition of CDH. We found that CDH utilizes β-D-xylopyranosyl-(1→4)-D-glucopyranose (Xyl-Glc) as an electron donor with similar Km and kcat values to cellobiose. β-D-Glucopyranosyl-(1→4)-D-xylopyranose (Glc-Xyl) shows a higher Km value, while xylobiose does not serve as a substrate. Trisaccharides show similar behavior; i.e., trisaccharides with cellobiose and Xyl-Glc units at the reducing end show similar kinetics, while the enzyme was less active towards those with Glc-Xyl, and inactive towards those with xylobiose. We also use docking simulation to evaluate substrate recognition of the disaccharides, and we discuss possible molecular mechanisms of substrate recognition by CDH.

著者

Kazuhiro Chiku Mami Wada Haruka Atsuji Arisa Hosonuma Mitsuru Yoshida Hiroshi Ono Motomitsu Kitaoka

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

pp.jag.JAG-2018_0002, (Released:2018-11-05)

被引用文献数

6

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We evaluated the stabilities of kojibiose and sophorose when heated under neutral pH conditions. Kojibiose and sophorose epimerized at the C-2 position of glucose on the reducing end, resulting in the production of 2-O-α-D-glucopyranosyl-D-mannose and 2-O-β-D-glucopyranosyl-D-mannose, respectively. Under weak alkaline conditions, kojibiose was decomposed due to heating into its mono-dehydrated derivatives, including 3-deoxy-2,3-unsaturated compounds and bicyclic 3,6-anhydro compounds. Following these experiments, we propose a kinetic model for the epimerization and decomposition of kojibiose and sophorose by heat treatment under neutral pH and alkaline conditions. The proposed model shows a good fit with the experimental data collected in this study. The rate constants of a reversible epimerization of kojibiose at pH 7.5 and 90 °C were (1.6 ± 0.1) × 10−5 s−1 and (3.2 ± 0.2) × 10−5 s−1 for the forward and reverse reactions, respectively, and were almost identical to those [(1.5 ± 0.1) × 10−5 s−1 and (3.5 ± 0.4) × 10−5 s−1] of sophorose. The rate constant of the decomposition reaction for kojibiose was (4.7 ± 1.1) × 10−7 s−1 whereas that for sophorose [(3.7 ± 0.2) × 10−6 s−1] was about ten times higher. The epimerization reaction was not significantly affected by the variation in the buffer except for a borate buffer, and depended instead upon the pH value (concentration of hydroxide ions), indicating that epimerization occurred as a function of the hydroxide ion. These instabilities are an extension of the neutral pH conditions for keto-enol tautomerization that are often observed under strong alkaline conditions.

著者

Motomitsu Kitaoka

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

vol.64, no.4, pp.99-107, 2017-11-20 (Released:2017-11-20)

参考文献数

18

被引用文献数

8

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3-Keto-levoglucosan (3ketoLG) has been postulated to be the product of a reaction catalyzed by levoglucosan dehydrogenase (LGDH), a bacterial enzyme involved in the metabolism of levoglucosan (LG). To investigate the LG metabolic pathway catalyzed by LGDH, 3ketoLG is needed. However, 3ketoLG has not been successfully isolated from the LGDH reaction. This study investigated the ability of pyranose oxidase to convert LG into 3ketoLG by oxidizing the C3 hydroxyl group. During the oxidation of LG, 3ketoLG was spontaneously crystallized in the reaction mixture. Starting with 500 mM LG, the isolation yield of 3ketoLG was 80 %. Nuclear magnetic resonance analyses revealed that a part of 3ketoLG dimerized in aqueous solution, explaining its poor solubility. Even under normal conditions, 3ketoLG was unstable in aqueous solution, with a half-life of 16 h at pH 7.0 and 30 °C. The decomposition proceeded through β-elimination of the C–O bonds at both C1 and C5, as evidenced by decomposition products. This instability explains the difficulty in obtaining 3ketoLG via the LGDH reaction.