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Probing the ubiquinol oxidatiousite of Eschenchia col ubiquinol oxidases.

探讨大肠埃希氏菌泛醇氧化酶的泛醇氧化位点。

基本信息

批准号：
08660136
负责人：
MIYOSHI Hideto
金额：
$ 1.6万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08660136/
关键词：
Respiratory chaiu Ubiquinone Terminal oxidase Structure activity relation

项目摘要

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.

用系统合成的泛喹酚类似物探索了大肠杆菌BO和BD型喹酚氧化酶的底物结合部位。泛喹酚-2衍生物对BO-型酶的表观K_m值远低于相应的6-正癸基衍生物。与具有相同碳数的饱和正烷基相比，类异戊二烯结构的疏水性较小，因此，天然的类异戊二烯侧链除了简单地增加分子的疏水性外，似乎在与苯二酚的结合中发挥了特殊的作用。无论侧链结构如何，2-甲氧基-3-乙氧基类似物的V&lt；max&gt；值均大于2-乙氧基-3-甲氧基类似物。这一结果不仅表明2-位上的甲氧基比3-位上的甲氧基更能被结合部位识别，而且侧链结构不影响对苯二酚环部分的结合。对5-位不同取代基的类似物的给电子活性进行了系统的分析，发现5-甲基对活性有重要影响。在与BD型酶的平行研究中，我们获得了类似的观察结果，除了几乎所有的喹酚类似物，但不是泛喹酚-1，在较高浓度下引起显著的底物抑制。这些结果表明，结构上不相关的两个末端氧化酶具有相同的结构性质，即对苯二酚的氧化点。