Pichorner H, Metodiewa D, Winterbourn C C
Department of Pathology, Christchurch School of Medicine, New Zealand.
Arch Biochem Biophys. 1995 Nov 10;323(2):429-37. doi: 10.1006/abbi.1995.0064.
Enzymatically generated tyrosyl radicals are effectively scavenged by reduced glutathione (GSH), thereby generating glutathione thiyl radicals and superoxide radicals, subsequently. Here, we have used horseradish peroxidase to generate tyrosyl radicals and investigated the fate of the superoxide radicals. At low GSH concentrations (with a maximum effect at 250 microM) a major reaction was between superoxide and the phenoxyl radical leading to a tyrosine peroxide. Formation of the peroxide was confirmed using a peroxide-specific colorimetric assay and detection of a new HPLC-peak. Its formation was inhibited by superoxide dismutase (SOD). The peroxide decomposed slowly in a reaction that was accelerated by GSH to give a new chromatographic peak. Increasing the GSH concentration decreased the amount of tyrosine peroxide formed and caused increases in rates of oxygen uptake and GSH oxidation. These increases were not seen in the presence of SOD and are consistent with GSH scavenging superoxide and leading to oxygen-dependent chain oxidation of GSH. Both pathways are undesirable for the cell and are effectively suppressed only if GSH as a radical scavenger acts in concert with SOD.
还原型谷胱甘肽（GSH）能有效清除酶促产生的酪氨酸自由基，从而生成谷胱甘肽硫自由基和超氧自由基。在此，我们利用辣根过氧化物酶生成酪氨酸自由基，并研究了超氧自由基的归宿。在低GSH浓度下（250微摩尔时效果最佳），超氧自由基与苯氧自由基之间的主要反应会生成酪氨酸过氧化物。使用过氧化物特异性比色法和检测新的高效液相色谱峰证实了过氧化物的形成。超氧化物歧化酶（SOD）可抑制其形成。过氧化物在GSH加速的反应中缓慢分解，产生一个新的色谱峰。增加GSH浓度会减少形成的酪氨酸过氧化物量，并导致氧气摄取速率和GSH氧化速率增加。在SOD存在的情况下未观察到这些增加，这与GSH清除超氧自由基并导致GSH的氧依赖性链氧化一致。这两条途径对细胞都是不利的，只有当作为自由基清除剂的GSH与SOD协同作用时，才能有效抑制它们。
