The reactions of hydrogen peroxide with bovine cytochrome c oxidase
The reactions of hydrogen peroxide with bovine cytochrome c oxidase
复制标题
DOI：
10.1016/s0005-2728(99)00105-x
复制
发表时间：
2000-01-03
影响因子：
4.3
通讯作者：
Rich, PR
中科院分区：
文献类型：
--
作者：
Jünemann, S;Heathcote, P;Rich, PR
已知氧化的细胞色素c氧化酶与两个过氧化氢分子反应，连续形成607 nm的“过氧”和580 nm的“铁基”物质。这些化合物被广泛用作催化循环的等效P和F中间体的模型化合物。然而，在pH 6.0-9.0范围内与H_2O_2反应的动力学分析揭示了更复杂的情况。特别地，随着pH降低，可以通过与单一H2 O2反应形成580-nm的化合物。这个物种，被称为F-，在光谱上与F相似但不完全相同这些反应与以前报道的大肠杆菌（T. Brittain，R.H.利特尔角Greenwood，N.J. Watmough，FEES Lett. 399（1996）21-25），其中建议F-。是直接从P.然而，在牛氧化酶F-。即使在低pH值下，CO/O-2处理产生的607-nm形式P-M的样品中也没有出现，尽管根据光谱特性和与H2 O2反应的动力学，这种形式显示出与H2 O2衍生的P态P-H相同。此外，降低在高pH下产生的P-M或P-H样品的pH导致F-。仅在几分钟的时间内形成。结果表明，P和F-。不是在一个快速的，pH值依赖的平衡，而是由不同的途径形成，不能以简单的方式相互转换，它们之间的关键区别在于它们的质子化模式。(C)2000 Elsevier Science B. V.保留所有权利。
Oxidised cytochrome c oxidase is known to react with two molecules of hydrogen peroxide to form consecutively 607 nm 'Peroxy' and 580-nm 'Ferryl' species. These are widely used as model compounds for the equivalent P and F intermediates of the catalytic cycle. However, kinetic analysis of the reaction with H2O2 ill the PH range 6.0-9.0 reveals a more complex situation. In particular, as the pH is lowered, a 580-nm compound can be formed by reaction with a single H2O2. This species, termed F-., is spectrally similar, but not identical, to F. The reactions are equivalent to those previously reported for the bo type quinol oxidase from Escherichia coli (T. Brittain, R.H. Little, C. Greenwood, N.J. Watmough, FEES Lett. 399 (1996) 21-25) where it was proposed that F-. is produced directly from P. However, in the bovine oxidase F-. does not appear in samples of the 607-nm form, P-M, produced by CO/O-2 treatment, even at low pH, although this form is shown to be identical to the H2O2-derived P state, P-H, on the basis of spectral characteristics and kinetics of reaction with H2O2. Furthermore, lowering the pH of a sample of P-M or P-H generated at high pH results in F-. formation only on a minutes time scale. It is concluded that P and F-. are not in a rapid, pH-dependent equilibrium, but instead are formed by distinct pathways and cannot interconvert in a simple manner, and that the crucial difference between them lies in their patterns of protonation. (C) 2000 Elsevier Science B.V. All rights reserved.