Cairns C B, Walther J, Harken A H, Banerjee A
Department of Surgery, University of Colorado Health Science Center, Denver 80262, USA.
Am J Physiol. 1998 May;274(5):R1376-83. doi: 10.1152/ajpregu.1998.274.5.R1376.
Mitochondria cannot maximize energy production, efficiency, and the cellular ATP phosphorylation potential all at the same time. The theoretical and observed determinations of coupling of oxidative phosphorylation in mitochondria from rat liver, heart, and brain were compared using classical and nonequilibrium thermodynamic measures. Additionally, the optimal thermodynamic efficiency and flow ratios were determined for control of the two energy-converting complexes of the respiratory chain: complex I (NADH), which reflects the integrated cellular pathway, and complex II (FADH2), the predominantly tricarboxylic acid (TCA) cycle pathway. For all three organs, the cellular respiratory pathway was more tightly coupled than the TCA pathway and resulted in a greater optimal efficiency. Liver mitochondria are the most thermodynamically efficient at ATP production using oxidative phosphorylation. Heart and brain mitochondrial systems utilize more oxygen, but can produce ATP at a faster rate than liver systems. Per the theory of economic degrees of coupling, isolated rat liver mitochondrial systems are designed for the economic production of ATP for use in cellular processes. In the brain, the mitochondrial TCA cycle pathway promotes the maximal maintenance of the cellular energy state for cellular viability, whereas in the heart the TCA cycle pathway maximizes the production of ATP. The coupling of oxidative phosphorylation not only can be expected to change with substrate availability but may also reflect an ontogenetic response of mitochondria to fit specific organ roles in the rat.
线粒体无法同时将能量产生、效率以及细胞ATP磷酸化潜力最大化。使用经典和非平衡热力学方法，对大鼠肝脏、心脏和大脑线粒体中氧化磷酸化偶联的理论测定值与观测值进行了比较。此外，还确定了呼吸链中两个能量转换复合体（复合体I（NADH），反映细胞整体代谢途径；复合体II（FADH2），主要参与三羧酸（TCA）循环途径）的最佳热力学效率和流量比。对于所有这三个器官，细胞呼吸途径的偶联比TCA途径更紧密，并且具有更高的最佳效率。肝脏线粒体在利用氧化磷酸化产生ATP方面具有最高的热力学效率。心脏和大脑的线粒体系统消耗更多氧气，但产生ATP的速度比肝脏系统更快。根据经济偶联度理论，分离的大鼠肝脏线粒体系统旨在经济地产生ATP以供细胞过程使用。在大脑中，线粒体TCA循环途径促进细胞能量状态的最大维持以确保细胞活力，而在心脏中，TCA循环途径使ATP的产生最大化。氧化磷酸化的偶联不仅预期会随着底物可用性的变化而改变，还可能反映线粒体对大鼠特定器官功能的个体发育响应。
