1991 Fiscal Year Final Research Report Summary
The molecular mechanism of electron transfer in mitochondria beta-oxidation
| Project/Area Number |
01570046
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
General physiology
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| Research Institution | Kumamoto University |
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Principal Investigator |
NISHINA Yasuzo Kumamoto University Medical School, Assoc. Prof., 医学部, 助教授 (50112553)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Kyosuke Kumamoto University Medical School, Joshu, 医学部, 助手 (80205905)
SHIGA Kiyoshi Kumamoto University Medical School, Prof., 医学部, 教授 (40028527)
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| Project Period (FY) |
1989 – 1991
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| Keywords | Flavoprotein / Raman Spectra / Acyl-CoA / FAD |
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| Research Abstract |
(1) Resonance Raman (RR) spectra of the complex of medium-chain acyl-CoA dehydrogenase with acetoacetyl-CoA and of the purple complex formed upon the addition of octanoyl-CoA to the dehydrogenase were obtained. The RR results confirm that the purple complex is a charge-transfer complex between the reduced enzyme and octenoyl-CoA derived from octanoyl-CoA. The large contribution of ionic resonance structure, C(2)=C(l)-O^-, for the ligands in both complexes, can be explained by the existence of an electrophilic group near the 0 atom of the C(l)=O group of the ligands and the electrostatic interaction between the group and the 0 atom of. ligand. This electrostatic interaction probably lowers the pKa value of a substrate at C(2)-H in an early step of reductive half reaction, facilitating the abstraction of alpha-proton.
(2) The association process of FAD and apo-electron-transferring flavoprotein (apoETF) was investigated. Kinetic studies suggest the existence of two different forms of apoETF, as represented in the following reaction scheme : A^* A, A + FAD HoloETF, where "A^*" and "A" are the different forms of apoETF. Anions induced the conversion from"A^*' to "A" ; the order of the effectiveness was I^- - Br^- > Cl^- > F^-. Glycerol also induced the conversion. The elution pattern of apoETF on a molecular sieve chromatography was changed by addition of salts or glycerol ; this change was due to the conversion from 'A^*" to "A" by the added solutes. "A^*" form was eluted out more rapidly than "A" form, indicating that "A^*" form exists in a relatively loose conformation than "A" form. The far-UV CD studies support this conclusion.
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