2004 Fiscal Year Final Research Report Summary
Structural and functional analysis of intermolecular Diels-Alderase
| Project/Area Number |
15370040
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Structural biochemistry
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
TANAKA Isao Hokkaido Univ., Grad.School of Sci., Prof., 大学院・理学研究科, 教授 (70093052)
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| Co-Investigator(Kenkyū-buntansha) |
YAO Min Hokkaido Univ., Grad.School of Sci., Inst., 大学院・理学研究科, 助手 (40311518)
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| Project Period (FY) |
2003 – 2004
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| Keywords | Diels-Alder reaction / natural Diels-Alderase / reaction mechanism / multi-step catalyst / secondary metabolite / macrophomate synthase / LUMO energy |
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| Research Abstract |
Diets-Alder reaction is a cycloaddition whose mechanism involves the overlap of the pi-orbitals of the two unsaturated systems in which an alkene (dienophile) adds to a 1,3-diene to form a 6-membered ring. The reaction is synthetically very useful because it forms cyclic products with high regio-and stereoselectivity under mild conditions. To investigate the catalytic mechanism of the natural Diels-Alderase, we initiated the crystal structure analysis of macrophomate synthase (MPS). Firstly we presented the X-ray crystal structure of this multifunctional enzyme. This is the first atomic resolution structure of the natural Diels-Alderase. The active site reveals several unexpected features for catalyzing the Diets-Alder reaction, including the existence of the residues for making catalytically important hydrogen bonds to the 2-pyrone. The electron-withdrawing groups at C3 and C5 of the 2-pyrone increase the reactivity of diene and moreover, the coordination of Lewis acid or the hydrogen bonding of solvent and catalytic residues in active site with the carbonyl groups effectively decreases the LUMO energy of the diene, resulting in an increase of the reactivity. We can see the advantage of natural enzymes compared to artificial catalytic antibodies ; the products of a first reaction catalyzed by these enzymes are trapped in an active site, overlapping of pi-orbitals with other moiety for a [4+2] reaction and forming two new carbon-carbon bonds. This type of natural Diels-Alderases has obvious advantage to utilize highly reactive substrate that is not stable in reaction medium.
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