Yagi T
Biochim Biophys Acta. 1984 Nov 26;767(2):288-94. doi: 10.1016/0005-2728(84)90198-1.
Reduction process of cytochrome c3 by hydrogenase (EC 1.12.2.1) under H2 was analyzed by means of spectrophotometry. When cytochrome c3 is in equilibrium with H2 under reduced pressure, spectral abnormality in the Soret region appeared most significantly in 1/4 reduction state, less significantly at 1/2 reduction state, and disappeared at 3/4 reduction state. The spectral changes during the enzymic reduction of cytochrome c3 in H2-saturated solution traced at several wavelengths also showed spectral abnormality in the Soret region at the early stage of reaction. The first-order rate constants for the successive reduction steps from all-ferric to all-ferrous form of cytochrome c3 was estimated to be k1 = 0.061 s-1, k2 = 0.063 s-1, k3 = 0.039 s-1 and k4 = 0.014 s-1 (cytochrome c3: 2 microM; hydrogenase: 2 nM, and at 20 degrees C, pH 7.0). Strong interaction is suggested between hemes 3 and 4 (for the refined structure and heme-numbering, see Higuchi, Y., Kusunoki, M., Matsuura, Y., Yasuoka, N. and Kakudo, M. (1984) J. Mol. Biol. 172, 109-139). The first electron from hydrogenase is supposed to be transferred to these hemes and delocalized between them, and the second electron, among hemes 3, 4 and 1. The characteristic behavior in the enzymic reduction of cytochrome c3 is different from that in non-enzymic reduction.
利用分光光度法分析了氢化酶（EC 1.12.2.1）在氢气存在下对细胞色素c3的还原过程。当细胞色素c3在减压下与氢气达到平衡时，索雷特区域的光谱异常在1/4还原状态时最为明显，在1/2还原状态时不太明显，而在3/4还原状态时消失。在几个波长下追踪氢气饱和溶液中细胞色素c3的酶促还原过程中的光谱变化，反应初期索雷特区域也出现了光谱异常。细胞色素c3从全铁形式连续还原为全亚铁形式的一级速率常数估计为k1 = 0.061 s-1、k2 = 0.063 s-1、k3 = 0.039 s-1和k4 = 0.014 s-1（细胞色素c3：2 μM；氢化酶：2 nM，20℃，pH 7.0）。推测血红素3和4之间存在强相互作用（关于精细结构和血红素编号，见Higuchi, Y., Kusunoki, M., Matsuura, Y., Yasuoka, N.和Kakudo, M. (1984) J. Mol. Biol. 172, 109 - 139）。来自氢化酶的第一个电子被认为转移到这些血红素上并在它们之间离域，第二个电子则在血红素3、4和1之间离域。细胞色素c3的酶促还原过程中的特征行为与非酶促还原过程中的不同。
