1997 Fiscal Year Final Research Report Summary
Probing the ubiquinol oxidatiousite of Eschenchia col ubiquinol oxidases.
| Project/Area Number |
08660136
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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 |
MIYOSHI Hideto KYOTO UNIVERSITY Graduate School of Agriculture, Associate Professor, 農学研究科, 助教授 (20190829)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Respiratory chaiu / Ubiquinone / Terminal oxidase / Structure activity relation |
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| Research Abstract |
Substrate binding sites of the Escherichia coli bo-and bd-type quinol oxidases were probed with systematically synthesized ubiquinol analogues. The apparent K_m values of ubiquinol-2derivatives to the bo-type enzyme were much lower than that of the corresponding 6-n-decyl derivatives. The isoprenoid structure is less hydrophobic than the saturated n-alkyl group with the same carbon, number, therefore, the native isoprenoid side chain appears to play a specific role in quinol binding besides simply increasing hydrophobicity of the molecule. The V_<max> values of 2-methoxy-3-ethoxy analogues were greater than that of 2-ethoxy-3-methoxy analogues irrespective of the side chain structure. This result indicates not only that a methoxy group in the 2-position is recognized more strictly than 3-position by the binding site, but also that the side chain structure does not affect binding of the quinol ring moiety. Systematic analysis of the electron-donating activities of the analogues with different substituents in the 5-position revealed that the 5-methyl group is important for the activity. In the parallel studies with the bd-type enzyme, we obtained similar observations except that almost all quinol analogues, but not ubiquinol-1, elicited a remarkable substrate inhibition at higher concentrations. These results indicate that the structurally unrelated two terminal oxidases share common structural properties for the quinol oxidation site.
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