The efficiencies of the component steps of oxidative phosphorylation. II. Experimental determination of the efficiencies in mitochondria and examination of the equivalence of membrane potential and pH gradient in phosphorylation.
The efficiencies of the component steps of oxidative phosphorylation. II. Experimental determination of the efficiencies in mitochondria and examination of the equivalence of membrane potential and pH gradient in phosphorylation.
复制标题
氧化磷酸化各组成步骤的效率。
DOI：
10.1016/0003-9861(86)90427-3
复制
发表时间：
1986
影响因子：
3.9
通讯作者：
Gunter,TE
中科院分区：
文献类型：
--
作者：
Jensen,BD;Gunter,KK;Gunter,TE
在随附的文章中（TE Gunter和BD詹森，1986 Arch.Biochem.Biophys. 248，289-304），描述了一种用于测量氧化磷酸化过程的各个步骤的效率的方法。应用这种方法的情况下，状态3磷酸化在大鼠肝线粒体的结果在这里报道。在梯度产生、泄漏和磷酸化步骤的能量使用（或功率使用）速率以表格形式报告为效率和能量使用因子。梯度生成和磷酸化步骤的耦合度的极限也被确定，并且在当前的测量条件下，发现这些耦合度相当接近于1。这些数据可以用来表明，同时符合热力学定律和现有数据的化学计量参数n H O（在这种情况下，从琥珀酸盐到氧的电荷/2 e −比）、n H P（H+ ATP比）和n H T（在底物-产物传输过程中转移的质子数）的唯一集合是8，3，1和6，3，0。对于分析的对照数据，磷酸化步骤的效率平均为80%，其与n H O和n H T无关。如果n H O为8（琥珀酸对氧），电化学质子梯度产生效率的平均值约为91%。由于非常少的功率（能量）然后将被留下以通过一些其他耦合手段与磷酸化并联耦合，这将使电化学质子梯度处于功率流的直接路径中，并将其识别为过程中的“一个”中间体。这表明任何其他中间体都应被视为与电化学质子梯度“串联”。已采用丁酸盐和丙酸盐试剂以允许在pH梯度和膜电位范围内进行研究。丁酸盐和丙酸盐都降低了电化学质子梯度的产生效率并增加了质子泄漏。通过丁酸盐调节pH梯度和膜电位值，可以看出，pH梯度用于磷酸化的效率与膜电位用于磷酸化的效率之比为1.08±0.38。
In the accompanying article (TE Gunter and BD Jensen, 1986 Arch. Biochem. Biophys. 248, 289–304), a method is described for measuring the efficiencies of individual steps of the process of oxidative phosphorylation. The results of applying this method to the case of state 3 phosphorylation in rat liver mitochondria are reported here. The rate of energy use (or power use) at the gradient generation, leakage, and phosphorylation steps are reported as efficiencies and energy use factors in tabular form. The limits of the degrees of coupling of the gradient generation and phosphorylation steps are also determined and under the current conditions of measurement these degrees of coupling are found to be quite close to unity. The data can be used to show that the only sets of the stoichiometric parameters n H O (the charge/2e− ratio in this case from succinate to oxygen), n H P (the H+ ATP ratio), and n H T (number of protons translocated during substrate-product transport) which are simultaneously consistent with both the laws of thermodynamics and with the current data are 8, 3, 1, and 6, 3, 0. The efficiency of the phosphorylation step which is independent of n H O and n H T averages 80% for the control data analyzed. If n H O is 8 (succinate to oxygen), the average value of the efficiency of generation of the electrochemical proton gradient is approximately 91 percent. Since very little power (energy) would then be left over to be coupled in parallel to phosphorylation through some other means of coupling, this would place the electrochemical proton gradient in the direct path of power flow and identify it as “an” intermediate in the process. This would suggest that any other intermediate should be considered as being “in series” with the electrochemical proton gradient. The agents butyrate and propionate have been employed to permit investigation over a range of pH gradient and membrane potential. Both butyrate and propionate decrease the efficiency of generation of the electrochemical proton gradient and increase proton leakage. In addition, butyrate activates electron transport whereas propionate inhibits it. By using butyrate to modify the values of pH gradient and membrane potential, it can be shown that the ratio of the efficiency with which the pH gradient is used in phosphorylation to that with which the membrane potential is used is 1.08±0.38.