Scholes T A, Hinkle P C
Biochemistry. 1984 Jul 3;23(14):3341-5. doi: 10.1021/bi00309a035.
The maximum Gibbs free energies of reverse electron transfer from succinate to NAD+ and from cytochrome c to fumarate driven by ATP hydrolysis in submitochondrial particles from beef heart were measured as a function of the Gibbs free energy of ATP hydrolysis. The ratio of the energies delta G'redox/delta G'ATP was 1.40 from succinate to NAD+ and 0.89 from cytochrome c to succinate. The ratio, equivalent to a thermodynamic P/2e-ratio, was dependent on whether the electrochemical proton gradient was primarily a membrane potential or a pH gradient for the cytochrome c to fumarate reaction. The results are consistent with H+/ATP = 3 for F1 ATPase, H+/2e- = 4 for NADH-CoQ reductase, and H+(matrix)/2e- = 2 for succinate-cytochrome c reductase.
测定了牛肉心亚线粒体颗粒中由ATP水解驱动的从琥珀酸到NAD⁺的反向电子转移以及从细胞色素c到延胡索酸的反向电子转移的最大吉布斯自由能，该自由能是ATP水解吉布斯自由能的函数。从琥珀酸到NAD⁺的能量ΔG'氧化还原/ΔG'ATP的比值为1.40，从细胞色素c到琥珀酸的比值为0.89。该比值等同于热力学P/2e⁻比值，对于细胞色素c到延胡索酸的反应，它取决于电化学质子梯度主要是膜电位还是pH梯度。结果与F1 ATP酶的H⁺/ATP = 3、NADH - 辅酶Q还原酶的H⁺/2e⁻ = 4以及琥珀酸 - 细胞色素c还原酶的H⁺(基质)/2e⁻ = 2一致。
