| Project/Area Number |
20K05875
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 38050:Food sciences-related
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| Research Institution | Ryukoku University (2021-2022)
Kyoto University (2020) |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Project Status |
Completed (Fiscal Year 2022)
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| Budget Amount *help |
¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
Fiscal Year 2022: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2021: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2020: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
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| Keywords | taste / sweet / atomic resolution / X-ray crystallography / 甘味 / ｐH変化 / 構造解析 / 甘味タンパク質 / 熱安定性 / ｐH / リシン残基 / 温度因子 / タンパク質 / 構造変化 / 耐熱性 / 甘味発現 / 苦味抑制 / 受容体複合体モデル |
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| Outline of Research at the Start |
タンパク質系甘味料であるソーマチンは強い甘味を呈すると共に、苦味抑制等の特有な機能を有するが、その甘味発現機構や味質改善機構は明らかとなっていない。ソーマチンと相同性の高い「ソーマチン様タンパク質」が植物に広く存在するが、その他多くの植物由来ソーマチン様タンパク質は、甘味や苦味抑制作用を示さず、食品素材としての利用は進んでいない。
本研究では、まず甘味発現に必須なアミノ酸側鎖のフレキシブルな構造を、生理的温度下かつ原子レベルで明らかにする。次に受容体複合体モデルを用いて、甘味性と耐熱性を高めるほか、苦味抑制の解明にも活用し、新規機能性タンパク質の創出を目指す。
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| Outline of Final Research Achievements |
The sweetness of thaumatin remains when heating under acidic conditions, but it disappears when heating at a pH above 7. To assess this phenomenon more in detail, X-ray crystal structures analysis and the melting temperature (Tm) of thaumatin were examined. The Tm of thaumatin at pH 4 was substantially reduced when compared to pH 6, suggesting thermal unfolding of thaumatin at pH 4 was occurred in lower temperature than at pH 6. The structural comparisons among different pH values revealed overall B-factor value of structure at pH 4 was indeed higher than those at pH 6 and 8, but the relative B-factor values for most lysine residues tended to decrease on lowering the pH. These results suggested that structure at pH 4 becomes more flexible and feasible to be unfolding than at pH 6.and 8, but reduction of relative flexibility of the specific lysine residues might play important roles to prevent thermal aggregation under acidic conditions, thereby maintain sweetness.
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| Academic Significance and Societal Importance of the Research Achievements |
原子レベルでの構造解析により、ソーマチンの熱安定性や、熱凝集に寄与する構造要因を明らかにすることで、その他多くの食品タンパク質に対しても、構造安定性の強化や熱凝集性を抑制できる手法を構築し、新規植物由来の食品素材の開発に繋げたい。
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