Effect of ring substituents on the transketolase-catalyzed conversion of nitroso aromatics to hydroxamic acids.
Effect of ring substituents on the transketolase-catalyzed conversion of nitroso aromatics to hydroxamic acids.
复制标题
环取代基对转酮酶催化亚硝基芳族化合物转化为异羟肟酸的影响。
DOI：
10.1016/0006-2952(86)90634-9
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发表时间：
1986
影响因子：
5.8
通讯作者：
Corbett,BR
中科院分区：
文献类型：
--
作者：
Corbett,MD;Corbett,BR
转酮醇酶催化八种不同的芳香族C-亚硝基化合物转化为相应的N-羟乙酰衍生的异羟肟酸。还发现三种亚硝基化合物通过还原过程部分转化为芳基羟胺。发现这些代谢物的生产速率与芳环上存在的取代基的电负性相关。这些取代亚硝基底物与转酮酶和果糖-6-磷酸的反应速率顺序为：4-NO_2> 4-CF_3> 3-CF_3，未取代的> 4-Cl > 4-CH_3，4-苯基> 4-OC_2 H_5。具有强吸电子基团4-NO2、4-CF 3和3-CF 3的底物是唯一被发现作为竞争过程经历酶促还原为羟胺的底物。提出了一种机制，涉及亚硝基底物和酶的中间体“活性乙醇醛”在转酮醇酶的活性位点之间的氧化还原反应。
Transketolase catalyzed the conversion of eight different aromatic C-nitroso compounds into the corresponding N-glycolyl derived hydroxamic acids. Three of the nitroso compounds were also found to be converted in part to the arylhydroxylamines by a reductive process. A correlation was found for the rates of production of these metabolites with the electronegatives of substituent groups that were present on the aromatic ring. The rates of reaction of these substituted nitroso substrates with transketolase andd-fructose-6-phosphate were found to decrease in the order 4-NO2> 4-CF3> 3-CF3, unsubstituted > 4-Cl > 4-CH3, 4-phenyl > 4-OC2H5.N,N-Dimethyl-p-nitrosoaniline was not metabolized by transketolase under the conditions employed for the other substrates. Those substrates possessing the strong electron-withdrawing groups 4-NO2, 4-CF3and 3-CF3were the only substrates that were found to undergo enzymatic reduction to the hydroxylamines as a competing process. A mechanism was proposed that involves a redox reaction between the nitroso substrate and the enzymatic intermediate “active glycolaldehyde” at the active-site of transketolase.