| Project/Area Number |
08660136
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Bioproduction chemistry/Bioorganic chemistry
|
|---|
| Research Institution | KYOTO UNIVERSITY |
|---|
Principal Investigator |
MIYOSHI Hideto KYOTO UNIVERSITY Graduate School of Agriculture, Associate Professor, 農学研究科, 助教授 (20190829)
|
|---|
| Project Period (FY) |
1996 – 1997
|
| Project Status |
Completed (Fiscal Year 1997)
|
| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
|---|
| Keywords | Respiratory chaiu / Ubiquinone / Terminal oxidase / Structure activity relation |
|---|
| 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.
|
