| Project/Area Number |
07660134
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Bioproduction chemistry/Bioorganic chemistry
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
KANO Kenji Kyoto Univ., Fac.Agriculture, Associate Professor, 農学部, 助教授 (10152828)
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| Co-Investigator(Kenkyū-buntansha) |
IKEDA Tokuji Kyoto Univ., Fac.Agriculture, Professor, 農学部, 教授 (40026422)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1996: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1995: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Quinonoid Cofactor / Quinoproteins / Catalytic Amine Oxidation / Redox Potentials / Ortho-quinones / Voltammetry / Column Electrolytic Spectroscopy / アミン酸化触媒反応 / キノプロティン / 電子状態 / 電子移動 |
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| Research Abstract |
1 Physicochemical and spectroscopic properties of tryptophan tryptophylquinone (TTQ), a cofactor bacterial methylamine dehydrogenase, have been elucidated in view of redox and acid-base reactions and semiquinone radical electronic structure. Reactivity of TTQ toward ammonia, as a substrate analog, has been also investigated. Significance of these physicochemical and structural properties have been detailed in relation with its function in the enzymatic reaction.
2 Column-electrolytic spectroscopy has been developed in order to obtain spectroelectrochemical property of quinones and related molecules. This method has been successfully applied to the thermodynamic analysis of the five-step electron transfer of a quinohemoprotein, alcohol dehydrogenase.
3 Several model compounds of topa quinone, a cofactor of copper amine oxidases, were synthesized. Detailed kinetic analysis has been performed concerning quinone-catalyzed amine oxidation using TTQ and TPQ model compounds as well as pyrroloqu
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inoline quinone (PQQ). A reaction intermediate radical generated during the catalytic reaction has been characterized using electron spin resonance spectroscopy. All these results strongly support a transamination mechanism.
4 Relation between the catalytic activity and electronic structure of quinones suggests the significance of ortho-quinone structures in expression of the catalytic amine oxidation activity. Tautomerization of free TPQ model compounds between ortho-and para-quinone-type electronic structures is responsible for their relatively low catalytic activity in the amine oxidation compared with TTQ and PQQ as rigorous ortho-quinones. On the other hand, it has been found that semiquinone radicals participates is autoxidation of reduced quinones.
5 On the basis of these results, roles of Cu (II) is proposed as a transient intramolecular electron acceptor in copper amine oxidases to enhance the reactivity toward dioxygen through the generation of the imino-TPQ semiquinone and as a weak ligand in TPQ-containing amine oxidases to make the TPQ cofactor to bear an ortho-quinone-type electronic structure. Less
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