Lesanavičius Mindaugas, Seo Daisuke, Čėnas Narimantas
Department of Xenobiotics Biochemistry, Institute of Biochemistry of Vilnius University, Saulėtekio 7, LT-10257 Vilnius, Lithuania.
Division of Material Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan.
Antioxidants (Basel). 2022 May 19;11(5):1000. doi: 10.3390/antiox11051000.
ferredoxin:NADP oxidoreductase (FNR) belongs to a novel group of thioredoxin reductase-type FNRs with partly characterized redox properties. Based on the reactions of FNR with the 3-acetylpyridine adenine dinucleotide phosphate redox couple, we estimated the two-electron reduction midpoint potential of the FAD cofactor to be -0.285 V. 5-Deaza-FMN-sensitized photoreduction revealed -0.017 V separation of the redox potentials between the first and second electron transfer events. We examined the mechanism of oxidation of FNR by several different groups of nonphysiological electron acceptors. The / values of quinones and aromatic -oxides toward FNR increase with their single-electron reduction midpoint potential. The lower reactivity, mirroring their lower electron self-exchange rate, is also seen to have a similar trend for nitroaromatic compounds. A mixed single- and two-electron reduction was characteristic of quinones, with single-electron reduction accounting for 54% of the electron flux, whereas nitroaromatics were reduced exclusively via single-electron reduction. It is highly possible that the FADH· to FAD oxidation reaction is the rate-limiting step during the reoxidation of reduced FAD. The calculated electron transfer distances in the reaction with quinones and nitroaromatics were close to those of and FNRs, thus demonstrating their similar "intrinsic" reactivity.
NADP氧化还原酶（FNR）属于一类新型的硫氧还蛋白还原酶型FNR，其氧化还原特性部分已得到表征。基于FNR与3-乙酰吡啶腺嘌呤二核苷酸磷酸氧化还原对的反应，我们估计FAD辅因子的双电子还原中点电位为-0.285V。5-脱氮-FMN敏化光还原显示，第一和第二电子转移事件之间的氧化还原电位分离为-0.017V。我们研究了几种不同组的非生理性电子受体对FNR的氧化机制。醌类和芳香族环氧化物对FNR的/值随其单电子还原中点电位的增加而增加。硝基芳香族化合物的反应性较低，反映出它们较低的电子自交换速率，也呈现出类似的趋势。醌类的特征是单电子和双电子还原混合，单电子还原占电子通量的54%，而硝基芳香族化合物仅通过单电子还原进行还原。在还原型FAD的再氧化过程中，FADH·到FAD的氧化反应极有可能是限速步骤。与醌类和硝基芳香族化合物反应中计算出的电子转移距离与[具体物质1]和[具体物质2]FNR的接近，从而证明了它们相似的“固有”反应性。
