Veuthey A L, Stucki J
Biophys Chem. 1987 Apr;26(1):19-28. doi: 10.1016/0301-4622(87)80003-0.
The buffering ability of the adenylate kinase reaction with respect to the phosphate potential and efficiency of oxidative phosphorylation in the presence of a fluctuating load conductance were studied by computer simulations. Fluctuations of the load conductance, i.e., of the irreversible ATP-utilizing reactions in the cell, were generated by integrating an Ornstein-Uhlenbeck diffusion process. This real or colored noise was then injected into the set of differential equations describing the rate laws for the changes of the adenine nucleotide concentrations based on a simple nonequilibrium thermodynamic model of oxidative phosphorylation. Numerical integration of this system of stochastic differential equations allowed us to investigate the influence of different parameters on the performance of this energy converter. Probability density estimates revealed that the variance of the efficiency about its optimal value was significantly reduced by the adenylate kinase reaction. It was found that the buffering ability of this enzyme is restricted to a specific frequency domain of the fluctuations of the load conductance. This frequency filtering was confirmed by substituting the random fluctuations of the load conductance by simple sinusoidal perturbations. All these studies revealed that for each domain of frequencies of the load perturbations there exists an optimal activity of the adenylate kinase which minimizes deviations from optimal efficiency of oxidative phosphorylation.
通过计算机模拟研究了腺苷酸激酶反应对磷酸盐电位的缓冲能力以及在负载电导波动情况下氧化磷酸化的效率。负载电导的波动，即细胞中不可逆的ATP利用反应的波动，是通过对奥恩斯坦-乌伦贝克扩散过程进行积分产生的。然后，基于氧化磷酸化的简单非平衡热力学模型，将这种真实噪声或有色噪声注入到描述腺嘌呤核苷酸浓度变化速率定律的微分方程组中。对这个随机微分方程组进行数值积分，使我们能够研究不同参数对这种能量转换器性能的影响。概率密度估计表明，腺苷酸激酶反应显著降低了效率围绕其最优值的方差。发现该酶的缓冲能力仅限于负载电导波动的特定频域。通过用简单的正弦扰动代替负载电导的随机波动，证实了这种频率滤波。所有这些研究表明，对于负载扰动的每个频率域，都存在一个腺苷酸激酶的最佳活性，它能使氧化磷酸化的效率偏离最优值的程度最小化。
