Electrochemical evaluation of the reaction rate between methyl viologen mediator and diaphorase enzyme for the electrocatalytic reduction of NAD+ and digital simulation for its voltammetric responses
Electrochemical evaluation of the reaction rate between methyl viologen mediator and diaphorase enzyme for the electrocatalytic reduction of NAD+ and digital simulation for its voltammetric responses
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DOI：
10.1016/s0022-0728(99)00074-1
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发表时间：
1999-04-29
影响因子：
4.5
通讯作者：
Kang, C
中科院分区：
文献类型：
--
作者：
Kim, S;Yun, SE;Kang, C
研究了黄递酶对NAD(+)的电催化还原作用。用甲基紫精作为电极和酶之间的电子转移媒介。用循环伏安法在金-汞齐电极上测定了NAD(+)还原的催化波，在负电位下背景电流很小。在扫描速度较慢、甲基紫精浓度较低、NAD(+)浓度较高的条件下，电极反应转变为电化学催化(EC‘)反应，可获得稳定的电流。由电流-[MV2+]斜率估算出还原甲基紫精与氧化黄递酶反应的双分子速率常数为7.50×10~(-3)M~(-1)S(-1)。电流对酶浓度平方根的另一个斜率也给出了接近的值，为6.7×10~3M~(-1)S(-1)。在计算速率常数时，考虑了不是一一对应时的化学计量因子。利用估算的反应速率常数，对所提出的反应机理进行了数字模拟，并与实验获得的伏安图进行了比较。结果表明，反应速率常数的估算方法和所提出的反应机理适用于酶催化的电化学反应。(C)1999 Elsevier Science S.A.保留所有权利。
The electrocatalytic reduction of NAD(+) using diaphorase enzyme was studied. Methyl viologen was used as an electron transfer mediator between an electrode and the enzyme. A catalytic wave for the reduction of NAD(+) when all the species were in the solution was measured with cyclic voltammetry at a gold-amalgam electrode which showed low background currents at negative potentials. Steady-state currents could be obtained under the conditions of slow scan rate, low methyl viologen concentration, and high NAD(+) concentration as the electrode reaction was converted to an electrochemical-catalytic (EC') reaction. The bimolecular rate constant for the reaction of the reduced methyl viologen with the oxidized diaphorase was estimated as 7.5 x 10(3) M-1 s(-1) from the slope of the current versus [MV2+] plot. Another slope of the current against the square root of the enzyme concentration also gave a close value of 6.7 x 103 M-1 s(-1). In the calculation of the rate constant, the stoichiometric factor when it is not one-to-one was considered. With the evaluated rate constant, digital simulation using the suggested reaction mechanism was compared with the experimentally obtained voltammograms. Satisfactory agreement indicates that the evaluation methods of the rate constant and the suggested mechanism are appropriate for the mediated enzyme-catalyzed electrochemical reactions. (C) 1999 Elsevier Science S.A. All rights reserved.