Maples K R, Mason R P
Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
J Biol Chem. 1988 Feb 5;263(4):1709-12.
Uric acid has previously been shown to act as a water-soluble antioxidant. Although the antioxidant activity of uric acid has been attributed to its ability to scavenge free radicals, the one-electron uric acid oxidation product of such a scavenging reaction has not been detected. It order to determine whether a free radical metabolite of uric acid could be formed via one-electron redox processes, we oxidized uric acid with potassium permanganate, horseradish peroxidase/hydrogen peroxide, and hematin/hydrogen peroxide systems. With the use of the rapid-mixing, continuous-flow electron spin resonance technique, we were able to detect the urate anion free radical in all three radical-generating systems. Based on N15-isotopic-labeling experiments, we show that the unpaired electron of this radical is located primarily on the five-membered ring of the purine structure. We were also able to demonstrate that this radical could be scavenged by ascorbic acid.
尿酸此前已被证明可作为一种水溶性抗氧化剂。尽管尿酸的抗氧化活性归因于其清除自由基的能力，但这种清除反应的单电子尿酸氧化产物尚未被检测到。为了确定尿酸的自由基代谢产物是否可通过单电子氧化还原过程形成，我们用高锰酸钾、辣根过氧化物酶/过氧化氢和血红素/过氧化氢体系氧化尿酸。通过使用快速混合、连续流动电子自旋共振技术，我们能够在所有三个自由基产生体系中检测到尿酸根阴离子自由基。基于N15同位素标记实验，我们表明该自由基的未成对电子主要位于嘌呤结构的五元环上。我们还能够证明这种自由基可被抗坏血酸清除。
