Stucki J W, Lehmann L H, Mani P
Biophys Chem. 1984 Mar;19(2):131-45. doi: 10.1016/0301-4622(84)85014-0.
The transient response of mitochondrial ATP production towards perturbations was studied by analyzing the trajectories leading from arbitrary initial conditions of the adenine nucleotide pool to the final steady state. These trajectories were calculated from differential equations based on linear relations between flows and thermodynamic forces of the adenylate kinase system including oxidative phosphorylation. The motion of the system along the trajectories consists of two phases: (1) a rapid phase leading from initial states to a common relaxation curve; and (2) a slow phase leading along the relaxation curve to the final steady state. The first phase corresponds to a motion close to the loci of constant adenylic energy charge. In line with this observation is the finding that the energy charge is a constant of motion of the adenylate kinase reaction. The second phase corresponds to a motion along a relaxation curve characterized by minimal Lyapunov exponents in the concentration space of the adenine nucleotides. Thus, both phases of the transient kinetics can be approximated in terms of thermodynamic functions to a high degree of precision. Incubations with isolated rat liver mitochondria were in excellent agreement with the theoretical predictions. In summary, these studies show that the adenylate kinase system not only optimizes the efficiency of oxidative phosphorylation through thermodynamic buffering but, in addition, also deeply influences the transient response of the whole system.
通过分析从腺嘌呤核苷酸池的任意初始条件到最终稳态的轨迹，研究了线粒体ATP产生对扰动的瞬态响应。这些轨迹是根据基于包括氧化磷酸化在内的腺苷酸激酶系统的流量与热力学力之间线性关系的微分方程计算得出的。系统沿轨迹的运动包括两个阶段：（1）从初始状态到共同弛豫曲线的快速阶段；（2）沿弛豫曲线到最终稳态的缓慢阶段。第一阶段对应于接近恒定腺苷酸能量电荷轨迹的运动。与此观察结果一致的是，能量电荷是腺苷酸激酶反应的运动常数。第二阶段对应于沿弛豫曲线的运动，该弛豫曲线在腺嘌呤核苷酸浓度空间中具有最小的李雅普诺夫指数。因此，瞬态动力学的两个阶段都可以在很大程度上用热力学函数近似。用分离的大鼠肝线粒体进行的孵育与理论预测非常吻合。总之，这些研究表明，腺苷酸激酶系统不仅通过热力学缓冲优化氧化磷酸化的效率，而且还深刻影响整个系统的瞬态响应。
