鹿児島大学 · 農学部 · 教授

研究キーワードglycoside hydrolases・gut microbiota・fructan metabolism・arabinan degradation・glycan structural analysis・oligosaccharide enzymes・carbohydrate biochemistry

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• Ishiwata A, Shite Y, Kitahara K, Tanaka K, Ito Y, Fujita K . Structural analysis of (2 → 1)-β-d-fructofuranosides linked to a terminal difructose dianhydride III produced by Bacteroides endo-t2025 · 担当区分： 最終著者, 責任著者 記述言語： 英語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： International Journal of Biological Macromolecules The glycoside hydrolase (GH) family 91 inulin fructotransferase (IFTase) complexes from Bacteroides ovatus and B. caccae act as endo-type IFTases targeting inulin. However, their degradation mechanism remains unclear. Herein, the exact structure of the accumulated inulin-degradation product in a culture supernatant is revealed as linear oligo-(2 → 1)-β-D-fructofuranosides linked to difructose dianhydride III (DFA III) at the reducing end. Additionally, we developed a method to quantify endo-IFTase activity by measuring DFA III released from inulin after sequential treatment with endo-IFTase and GH32 β-D-fructofuranosidase. Using this approach, we investigated the effect of varying concentrations of endo-IFTase subunits 1 and 2 and found that an equimolar mixture of the two subunits exhibited the highest enzymatic activity, indicating that the active complex forms in a 1:1 ratio. The endo-IFTase accepts fructooligosaccharide DP7 (GF6) as the shortest substrate, suggesting that the complex recognizes the region between subsites +3 and − 3. This study provides insights into the understanding of inulin degradation by Bacteroides species and elucidates the molecular mechanisms underlying prebiotic effects of inulin. DOI： 10.1016/j.ijbiomac.2025.143064 Scopus PubMed
• Lee S., Leclercq L.D., Guerardel Y., Szymanski C.M., Hurtaux T., Doering T.L., Katayama T., Fujita K., Aoki K., Aoki-Kinoshita K.F. . MicroGlycoDB: A database of microbial glycans using Semant2024 · 記述言語： 日本語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： BBA Advances Glycoconjugates are present on microbial surfaces and play critical roles in modulating interactions with the environment and the host. Extensive research on microbial glycans, including elucidating the structural diversity of the glycan moieties of glycoconjugates and polysaccharides, has been carried out to investigate the function of glycans in modulating the interactions between the host and microbes, to explore their potential applications in the therapeutic targeting of pathogenic species, and in the use as probiotics in gut microbiomes. However, glycan-related information is dispersed across numerous databases and a vast amount of literature, which makes it laborious and time-consuming to identify and gather the relevant information about microbial glycosylation. This challenge can be addressed by a comprehensive database, which could offer insight into the fundamental processes underlying glycosylation. We have developed a MicroGlycoDB database to provide integrated glycan information on important model microorganisms. The data is described using Semantic Web Technologies, which allow microbial glycan data to be represented in a structured format accessible by machines, thus facilitating data sharing and integration with other resources that catalog features such as pathways, diseases, or interactions. This semantic data based on ontologies will contribute to the discovery of new knowledge in the field of microbiology, along with the expansion of information on the glycosylation of other microorganisms. DOI： 10.1016/j.bbadva.2024.100126 Scopus PubMed
• Sasaki Y., Matsuo A., Hashiguchi M., Fujimura K., Koshino H., Tanaka K., Ito Y., Kitahara K., Ishiwata A., Fujita K. . Structural analysis of gum arabic side chains from Acacia seyal released2024 · 担当区分： 最終著者, 責任著者 記述言語： 日本語 掲載種別： 研究論文（学術雑誌） 出版者・発行元： Carbohydrate Polymers Gum arabic is widely used in the food and beverage industries for its emulsifying, stabilizing, and prebiotic effects, which promote Bifidobacterium growth. The two commercially approved varieties of gum arabic, namely, Acacia senegal gum and A. seyal gum, predominantly consist of arabinogalactan protein (AGP), albeit with different side chain modifications. We previously characterized two enzymes belonging to glycoside hydrolase (GH) family 39 in bifidobacteria involved in the release of α-D-Gal-(1→3)-α-L-Ara and β-L-Arap-(1→3)-α-L-Ara from the side chains of A. senegal gum. Although the carbohydrate structure of A. senegal gum is being increasingly explored, limited information is available on A. seyal gum. In this study, we discovered a novel GH39 β-arabino-oligosaccharide 3-O-β-L-arabinopyranosyl-α-L-arabinofuranosidase from Bifidobacterium catenulatum and revealed the accurate structure of β-L-arabino-oligosaccharides released from A. seyal gum as [β-L-Araf-(1→2)-]n-β-L-Arap-(1→3)-α-L-Araf-(1→) (n = 0–3). Growth assays and intracellular enzyme activity assessments using B. catenulatum revealed that β-L-arabino-oligosaccharides were degraded to L-arabinose by GH127 β-L-arabinofuranosidase and GH36 β-L-arabinopyranosidase. This study provides new insights into the diversity of AGP structures and the utilization mechanisms of A. seyal gum in bifidobacteria. DOI： 10.1016/j.carbpol.2024.122965 Scopus PubMed
• Ishiwata, A., Fukushima, R., Fushinobu, S., Fujita, K., Tanaka, K., Ito, Y.2023 · 記述言語： 英語

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• 新規アラビノビオース遊離酵素により解き明かすビフィズス菌のAGP分解メカニズム2019 · 研究課題/領域番号： 19K05816 2019年4月 - 2022年3月

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