Prasad M R, Engelman R M, Jones R M, Das D K
Department of Surgery, University of Connecticut School of Medicine, Farmington 06302.
Biochem J. 1989 Nov 1;263(3):731-6. doi: 10.1042/bj2630731.
We have examined the effects of O2-derived free radicals on oxymyoglobin, the myocardial intracellular protein involved in the storage and transport of O2. The oxyradicals generated by the xanthine/xanthine oxidase system decreased the concentration of oxymyoglobin. Based on the decreases in absorbance peaks at 581 nm and 415 nm it is estimated that out of a 10 nmol decrease in oxymyoglobin, 5 nmol appears to be oxidized to ferrimyoglobin (deoxygenation), while haem was removed from the other 5 nmol of haem protein. These processes were inhibited by both catalase alone and superoxide dismutase in combination with catalase, but not by either superoxide dismutase alone or deferoxamine. These results suggest that among H2O2, OH. and O2.-, only H2O2 causes the removal of haem and the oxidation of oxymyoglobin. Furthermore, the oxyradicals also released 3 microM free iron from oxymyoglobin, which is at least 5-fold less than the 15 nmol loss of oxymyoglobin. The loss of oxymyoglobin also preceded the release of free iron. These results indicate that oxymyoglobin oxidation and haem removal occur before the removal of free iron. Thus myoglobin appears to be highly susceptible to free radical attack, and this may represent yet another mechanism of free radical-mediated cellular injury.
我们研究了氧衍生的自由基对氧合肌红蛋白的影响，氧合肌红蛋白是参与氧气储存和运输的心肌细胞内蛋白质。黄嘌呤/黄嘌呤氧化酶系统产生的氧自由基降低了氧合肌红蛋白的浓度。根据581nm和415nm处吸光度峰值的下降估计，在氧合肌红蛋白减少10nmol中，有5nmol似乎被氧化为高铁肌红蛋白（脱氧），而另一半5nmol的血红素蛋白中的血红素被去除。单独的过氧化氢酶以及超氧化物歧化酶与过氧化氢酶联用均可抑制这些过程，但单独使用超氧化物歧化酶或去铁胺则无此作用。这些结果表明，在H2O2、OH·和O2-中，只有H2O2会导致血红素的去除和氧合肌红蛋白的氧化。此外，氧自由基还从氧合肌红蛋白中释放出3μM游离铁，这比氧合肌红蛋白损失的15nmol至少少5倍。氧合肌红蛋白的损失也先于游离铁的释放。这些结果表明，氧合肌红蛋白氧化和血红素去除发生在游离铁去除之前。因此，肌红蛋白似乎对自由基攻击高度敏感，这可能代表了自由基介导的细胞损伤的另一种机制。
