Lu Haiyun, Li Zhen, Hu Naifei
Department of Chemistry, Beijing Normal University, Beijing 100875, PR China.
Biophys Chem. 2003 Jul 1;104(3):623-32. doi: 10.1016/s0301-4622(03)00121-2.
The direct voltammetry and electrocatalytic properties of catalase (Cat) in polyacrylamide (PAM) hydrogel films cast on pyrolytic graphite (PG) electrodes were investigated. Cat-PAM film electrodes showed a pair of well-defined and nearly reversible cyclic voltammetry peaks for Cat Fe(III)/Fe(II) redox couples at approximately -0.46 V vs. SCE in pH 7.0 buffers. The electron transfer between catalase and PG electrodes was greatly facilitated in the microenvironment of PAM films. The apparent heterogeneous electron transfer rate constant (k(s)) and formal potential (E degrees ') were estimated by fitting square wave voltammograms with non-linear regression analysis. The formal potential of Cat Fe(III)/Fe(II) couples in PAM films had a linear relationship with pH between pH 4.0 and 9.0 with a slope of -56 mV pH(-1), suggesting that one proton is coupled with single-electron transfer for each heme group of catalase in the electrode reaction. UV-Vis absorption spectroscopy demonstrated that catalase retained a near native conformation in PAM films at medium pH. The embedded catalase in PAM films showed the electrocatalytic activity toward dioxygen and hydrogen peroxide. Possible mechanism of catalytic reduction of H(2)O(2) at Cat-PAM film electrodes was proposed.
研究了在热解石墨（PG）电极上浇铸的聚丙烯酰胺（PAM）水凝胶膜中过氧化氢酶（Cat）的直接伏安法和电催化性能。在pH 7.0缓冲液中，相对于饱和甘汞电极（SCE），Cat-PAM膜电极在约-0.46 V处显示出一对明确且近乎可逆的过氧化氢酶Fe(III)/Fe(II)氧化还原对的循环伏安峰。在PAM膜的微环境中，过氧化氢酶与PG电极之间的电子转移得到了极大促进。通过非线性回归分析拟合方波伏安图来估算表观异相电子转移速率常数（k(s)）和形式电位（E°'）。在pH 4.0至9.0之间，PAM膜中过氧化氢酶Fe(III)/Fe(II)对的形式电位与pH呈线性关系，斜率为-56 mV pH(-1)，这表明在电极反应中，过氧化氢酶的每个血红素基团的单电子转移与一个质子耦合。紫外可见吸收光谱表明，在中等pH值下，过氧化氢酶在PAM膜中保留了接近天然的构象。PAM膜中包埋的过氧化氢酶对氧气和过氧化氢表现出电催化活性。提出了Cat-PAM膜电极上催化还原H(2)O(2)的可能机制。
