Winterbourn C C, Metodiewa D
Department of Pathology, Christchurch School of Medicine, New Zealand.
Arch Biochem Biophys. 1994 Nov 1;314(2):284-90. doi: 10.1006/abbi.1994.1444.
Superoxide, generated by a xanthine oxidase/hypoxanthine system, reacts with reduced glutathione (GSH) to cause an increase in oxygen consumption and oxidized glutathione (GSSG) formation, both of which are fully inhibited by superoxide dismutase. In this study we have shown that little, if any, of the additional oxygen consumed is converted to hydrogen peroxide. We have confirmed that approximately 90% of the GSH is oxidized to GSSG, the remainder being converted to the sulfonic acid. Approximately 1.2 mol of GSSG was formed for each additional mole of oxygen consumed in the presence of GSH. The efficiency of the reaction increased with increasing GSH concentration (1-8 mM), pH, and pO2 and with decreasing superoxide generation rate. The results are consistent with a superoxide-dependent chain that does not produce hydrogen peroxide and that is terminated primarily by superoxide dismutation. We propose that this occurs via an initial reaction of superoxide with GSH to produce a sulfinyl radical rather than hydrogen transfer to give the thiyl radical. Our data suggest a rate constant for the superoxide/GSH reaction in the 10(2)-10(3) M-1s-1 range. GSH at the millimolar concentrations found intracellular should react with superoxide, but because superoxide is regenerated, it will not be an effective scavenger. Physiologically, superoxide dismutase is required to prevent chain oxidation of GSH.
由黄嘌呤氧化酶/次黄嘌呤系统产生的超氧化物与还原型谷胱甘肽（GSH）反应，导致耗氧量增加和氧化型谷胱甘肽（GSSG）生成，这两者均被超氧化物歧化酶完全抑制。在本研究中，我们已表明，额外消耗的氧气中即使有也很少转化为过氧化氢。我们已证实，约90%的GSH被氧化为GSSG，其余部分转化为磺酸。在GSH存在的情况下，每额外消耗1摩尔氧气大约会形成1.2摩尔GSSG。反应效率随GSH浓度（1 - 8 mM）、pH和pO₂的增加以及超氧化物生成速率的降低而提高。结果与一个不产生过氧化氢且主要通过超氧化物歧化终止的超氧化物依赖性链一致。我们提出，这是通过超氧化物与GSH的初始反应产生一个亚磺酰基自由基而不是通过氢转移产生硫自由基来实现的。我们的数据表明超氧化物/GSH反应的速率常数在10² - 10³ M⁻¹s⁻¹范围内。细胞内发现的毫摩尔浓度的GSH应与超氧化物反应，但由于超氧化物会再生，它不会是一种有效的清除剂。在生理上，需要超氧化物歧化酶来防止GSH的链式氧化。
