谷胱甘肽还原马心铁细胞色素c的动力学及机制

Kinetics and mechanism of the reduction of horse heart ferricytochrome c by glutathione.

作者信息

Everse J, Kujundzic N

出版信息

Biochemistry. 1979 Jun 12;18(12):2668-73. doi: 10.1021/bi00579a037.

Abstract

A detailed investigation of the reduction of cytochrome c by glutathione has shown that the reaction proceeds through several steps. A rapid combination of the reducing agent with the cytochrome leads to the formation of a glutathione-cytochrome intermediate in which the glutathione most likely interacts with the edge of the heme moiety. The electron transfer takes place in a subsequent slower step. Since cytochrome c(III) exists in two conformational forms at neutral pH [Kujundzic, N., & Everse, J. (1978) Biochem. Biophys. Res. Commun. 82, 1211], the reduction of cytochrome c by glutathione may be represented by cyt c(III) + GS- reversible K1 cyt c(III) ... GS- reversible k1 products cyt c*(III) + GS- reversible K2 cyt c*(III) ... GS- reversible k2 products At 25 degrees C, pH 7.5, and an ionic strength of 1.0 (NaCl), k1 = 1.2 X 10(-3) S-1, k2 = 2.0 X 10(-3) S-1, k1 = 2.9 X 10(3) M-1, and K2 = 5.3 X 10(3) M-1. The reaction is catalyzed by trisulfides, and second-order rate constants of 4.55 X 10(3) and 7.14 X 10(3) M-1 S-1 were obtained for methyl trisulfide and cysteine trisulfide, respectively.

摘要

对谷胱甘肽还原细胞色素c的详细研究表明，该反应通过几个步骤进行。还原剂与细胞色素的快速结合导致形成谷胱甘肽 - 细胞色素中间体，其中谷胱甘肽很可能与血红素部分的边缘相互作用。电子转移在随后较慢的步骤中发生。由于细胞色素c(III)在中性pH下以两种构象形式存在[库君季奇，N.，& 埃弗斯，J.（1978年）《生物化学与生物物理研究通讯》82，1211]，谷胱甘肽还原细胞色素c的过程可表示为：细胞色素c(III)+谷胱甘肽硫醚可逆K1 细胞色素c(III)…谷胱甘肽硫醚可逆k1 产物细胞色素c*(III)+谷胱甘肽硫醚可逆K2 细胞色素c*(III)…谷胱甘肽硫醚可逆k2 产物在25℃、pH 7.5和离子强度为1.0（氯化钠）的条件下，k1 = 1.2×10⁻³ s⁻¹，k2 = 2.0×10⁻³ s⁻¹，K1 = 2.9×10³ M⁻¹，K2 = 5.3×10³ M⁻¹。该反应由三硫化物催化，甲基三硫化物和半胱氨酸三硫化物的二级速率常数分别为4.55×10³ 和7.14×10³ M⁻¹ s⁻¹。