Patel R P, Svistunenko D A, Darley-Usmar V M, Symons M C, Wilson M T
Department of Biological and Chemical Sciences, University of Essex, Colchester, UK.
Free Radic Res. 1996 Aug;25(2):117-23. doi: 10.3109/10715769609149916.
The formation and reactivity of ferryl haemoglobin (and myoglobin), which occurs on addition of H2O2, has been proposed as a mechanism contributing to oxidative stress associated with human diseases. However, relatively little is known of the reaction between hydrogen peroxide and human haemoglobin. We have studied the reaction between hydrogen peroxide and purified (catalase free) human metHbA. Addition of H2O2 resulted in production of both ferryl haem iron (detected by optical spectroscopy) and an associated protein radical (detected by EPR spectroscopy). Titrating metHbA with H2O2 showed that maximum ferryl levels could be obtained at a 1:1 stoichiometric ratio of haem to H2O2. No oxygen was evolved during the reaction, indicating that human metHbA does itself not possess catalytic activity. The protein radicals obtained in this reaction reached a steady state concentration, during hydrogen peroxide decomposition, but started to decay once the hydrogen peroxide had been completely exhausted. The presence of catalase, at concentrations around 10(4) fold lower than metHb, increased the apparent stoichiometry of the reaction to 1 mol metHb: approximately 20 mol H2O2 and abolished the protein radical steady state. The biological implications for these results are discussed.
在添加过氧化氢时会形成高铁血红蛋白（和肌红蛋白）并具有反应活性，这一过程被认为是导致与人类疾病相关的氧化应激的一种机制。然而，关于过氧化氢与人类血红蛋白之间的反应，人们了解得相对较少。我们研究了过氧化氢与纯化的（不含过氧化氢酶）人高铁血红蛋白A之间的反应。添加过氧化氢会导致产生高铁血红素铁（通过光谱学检测）和一种相关的蛋白质自由基（通过电子顺磁共振光谱检测）。用过氧化氢滴定高铁血红蛋白A表明，在血红素与过氧化氢的化学计量比为1:1时可获得最大高铁水平。反应过程中没有氧气释放，这表明人高铁血红蛋白本身不具有催化活性。在过氧化氢分解过程中，该反应中获得的蛋白质自由基达到稳定状态浓度，但一旦过氧化氢完全耗尽，就开始衰减。过氧化氢酶的存在，其浓度比高铁血红蛋白低约10^4倍，将反应的表观化学计量比提高到1摩尔高铁血红蛋白：约20摩尔过氧化氢，并消除了蛋白质自由基的稳定状态。本文讨论了这些结果的生物学意义。
