不同类型细胞色素c与铁氰化物的氧化还原反应比较。

Biochim Biophys Acta. 1981 Jan 14;634(1):93-104. doi: 10.1016/0005-2728(81)90130-4.

The dynamic behavior of various types of cytochromes c in the redox reaction with iron hexacyanides was studied using a temperature-jump method in order to elucidate the molecular mechanism of the redox reaction of cytochromes with their oxidoreductants. Transmittance after the temperature jump changed through a single exponential decay for all cytochromes investigated. Under a constant concentration of anion, the redox reaction of various types of cytochrome c with iron hexacyanides was analyzed according to the scheme: (see formula in text) where C(III) and C(II) are ferric and ferrous cytochromes, respectively, Fe(III) and Fe(II) are ferri- and ferrocyanides, respectively, C(III) . Fe(II) is the ferricytochrome-ferrocyanide complex and C(II) . Fe(III) is the ferrocytochrome-ferricyanide complex. When step B is slower than the other two steps A and C, tau-1 can be represented approximately as (see formula in text) where the bar over the variables denotes the equilibrium value. In a large excess of ferrocyanide against cytochrome, we can estimate kappa 2, kappa-2, K1 and K3 independently. In the case of horse cytochrome c at 18 degrees C in 0.1 M phosphate buffer at pH 7 with 0.3 M KNO3, the estimated parameters are kappa 2 = 100 +/- 50 S-1, kappa-2 = (3.5 +/- 1.0) . 10(3) S-1, K1 = 15 +/- 7 M-1 and K3 = (8.5 +/- 1.5). 10(-4) M. From the same experiments for seven cytochromes (cytochrome c from horse, tuna, Candida krusei, Saccharomyces oviformis, Rhodospirillum rubrum cytochrome c2, Spirulina platensis cytochrome c-554 and Thermus thermophilus cytochrome c-552), the following results can be deduced. (1) Each parameter defined in the scheme above (kappa 2, kappa-2, K1, K3) diverged beyond the error range. Above all, kappa 2 values of cytochromes c-554 and c-552 are as large as 1 . 10(4) S-1 and much larger than those for the other cytochromes (to 50 approx. 700 S-1). (2) The variance of kappa 2K1 and kappa-2/K3 are relatively less than the variances of individual parameters (kappa 2, kappa-2, K1 and K3), which suggests that the values of kappa 2K1 and kappa-2/K3 have been conserved during the course of evolution.

为阐明细胞色素与其氧化还原酶之间氧化还原反应的分子机制，采用温度跃变方法研究了各种类型细胞色素c与铁氰化物氧化还原反应中的动力学行为。对于所有研究的细胞色素，温度跃变后的透光率通过单指数衰减变化。在阴离子浓度恒定的情况下，根据以下反应式分析各种类型的细胞色素c与铁氰化物的氧化还原反应：（见原文公式）其中C(III)和C(II)分别是高铁细胞色素和亚铁细胞色素，Fe(III)和Fe(II)分别是铁氰化物和亚铁氰化物，C(III).Fe(II)是高铁细胞色素 - 亚铁氰化物复合物，C(II).Fe(III)是亚铁细胞色素 - 铁氰化物复合物。当步骤B比其他两个步骤A和C慢时，τ - 1可近似表示为（见原文公式）其中变量上方的横线表示平衡值。在亚铁氰化物相对于细胞色素大量过量的情况下，我们可以独立估计κ2、κ - 2、K1和K3。在18℃下，于pH 7的0.1 M磷酸盐缓冲液中，含0.3 M KNO3的马细胞色素c的情况下，估计的参数为κ2 = 100 ± 50 S-1，κ - 2 = (3.5 ± 1.0).10(3) S-1，K1 = 15 ± 7 M-1，K3 = (8.5 ± 1.5).10(-4) M。通过对七种细胞色素（马、金枪鱼、克鲁斯假丝酵母、卵形酵母、深红红螺菌细胞色素c2、钝顶螺旋藻细胞色素c - 554和嗜热栖热菌细胞色素c - 552的细胞色素c）进行相同实验，可得出以下结果。(1) 上述反应式中定义的每个参数（κ2、κ - 2、K1、K3）的差异超出误差范围。最重要的是，细胞色素c - 554和c - 552的κ2值高达1.10(4) S-1，远大于其他细胞色素的κ2值（约50至700 S-1）。(2) κ2K1和κ - 2/K3的方差相对小于各个参数（κ2、κ - 2、K1和K3）的方差，这表明κ2K1和κ - 2/K3的值在进化过程中得以保留。