Laulhère J P, Barcelò F, Fontecave M
Chimie Bioinorganioque, LEDSS, Université J. Fourier, URA CNRS 0332, Grenoble, France.
Biometals. 1996 Jul;9(3):303-9. doi: 10.1007/BF00817931.
The function of ferritins is to store and release ferrous iron. During oxidative iron uptake, ferritin tends to lower Fe2+ concentration, thus competing with Fenton reactions and limiting hydroxy radical generation. When ferritin functions as a releasing iron agent, the oxidative damage is stimulated. The antioxidant versus pro-oxidant functions of ferritin are studied here in the presence of Fe2+, oxygen and reducing agents. The Fe(2+)-dependent radical damage is measured using supercoiled DNA as a target molecule. The relaxation of supercoiled DNA is quantitatively correlated to the concentration of exogenous Fe2+, providing an indirect assay for free Fe2+. After addition of ferrous iron to ferritin, Fe2+ is actively taken up and asymptotically reaches a stable concentration of 1-5 microM. Comparable equilibrium concentrations are found with plant or horse spleen ferritins, or their apoferritins. After addition of ascorbate, iron release is observed using ferrozine as an iron scavenger. Rates of iron release are dependent on ascorbate concentration. They are about 10 times larger with pea ferritin than with horse ferritin. In the absence of ferrozine, the reaction of ascorbate with ferritins produces a wave of radical damage; its amplitude increases with increased ascorbate concentrations with plant ferritin; the damage is weaker with horse ferritin and less dependent on ascorbate concentrations.
铁蛋白的功能是储存和释放亚铁离子。在氧化性铁摄取过程中，铁蛋白倾向于降低Fe2+浓度，从而与芬顿反应竞争并限制羟基自由基的产生。当铁蛋白作为铁释放剂发挥作用时，会刺激氧化损伤。本文在存在Fe2+、氧气和还原剂的情况下研究了铁蛋白的抗氧化与促氧化功能。使用超螺旋DNA作为靶分子来测量Fe(2+)依赖性自由基损伤。超螺旋DNA的松弛与外源Fe2+的浓度定量相关，为游离Fe2+提供了一种间接检测方法。向铁蛋白中添加亚铁离子后，Fe2+会被主动摄取并渐近地达到1-5 microM的稳定浓度。植物或马脾铁蛋白及其脱铁铁蛋白具有相当的平衡浓度。添加抗坏血酸后，使用亚铁嗪作为铁清除剂观察到铁的释放。铁释放速率取决于抗坏血酸浓度。豌豆铁蛋白的铁释放速率约为马铁蛋白的10倍。在没有亚铁嗪的情况下，抗坏血酸与铁蛋白的反应会产生一波自由基损伤；其幅度随植物铁蛋白抗坏血酸浓度的增加而增加；马铁蛋白的损伤较弱且对抗坏血酸浓度的依赖性较小。
