Albery W J, Cass A E, Shu Z X
Department of Chemistry, Imperial College, London, UK.
Biosens Bioelectron. 1990;5(5):379-95. doi: 10.1016/0956-5663(90)80017-8.
An inhibition enzyme electrode to measure toxic gases can be constructed using the respiratory enzyme cytochrome oxidase. The rate of enzyme turnover is followed by reducing cytochrome c on a gold electrode modified with the mediator bis(4-pyridyl) disulphate. The kinetics and mechanism of the system have been measured. The electrochemical kinetics for the oxidation of cytochrome c have been studied by rotating disc voltammetry and are shown to obey the Koutecky-Levich equation. The standard electrochemical rate constant is found to be 3 x 10(-3) cms-1. At ambient oxygen concentration the orders of the current with respect to the concentration of cytochrome oxidase, cytochrome c and oxygen are found to be 1/2, 1/2 and zero respectively. These orders are consistent with the rate limiting step being the turnover of the enzyme under saturated conditions in a thin reaction layer close to the electrode. At lower oxygen concentrations a good fit between the experimental results and a theoretical model further confirms the assignation of the mechanism. The rate constants describing the oxidation and reduction of the enzyme have been measured. The pH dependence of the current has been studied.
可使用呼吸酶细胞色素氧化酶构建用于测量有毒气体的抑制酶电极。通过在经介体双（4 - 吡啶基）二硫酸盐修饰的金电极上还原细胞色素c来跟踪酶的周转速率。已测量了该系统的动力学和机理。通过旋转圆盘伏安法研究了细胞色素c氧化的电化学动力学，结果表明其服从库特基 - 列维奇方程。发现标准电化学速率常数为3×10⁻³ cm s⁻¹。在环境氧浓度下，发现电流相对于细胞色素氧化酶、细胞色素c和氧浓度的级数分别为1/2、1/2和零。这些级数与限速步骤是在靠近电极的薄反应层中饱和条件下酶的周转一致。在较低氧浓度下，实验结果与理论模型之间的良好拟合进一步证实了该机理的归属。已测量了描述酶氧化和还原的速率常数。研究了电流对pH的依赖性。
