Abstract：
In this study, inactivation of mushroom polyphenol oxidase (PPO) by low intensity direct current (DC) electric field and its molecular mechanism were investigated. In the experiments under 3 V/cm, 5 V/cm, 7 V/cm and 9 V/cm electric fields, PPOs were all completely inactivated after different exposure times. Under 1 V/cm, a residual activity of 11.88 % remained. The inactivation kinetics confirms to Weibull model. Under 1-7 V/cm, n value closes to a constant about 1.3. The structural analysis of PPO under 3 V/cm and 5 V/cm by fluorescence emission spectroscopy and molecular dynamics (MD) simulation showed that the tertiary structure was slightly changed with increased radius of gyration, higher potential energy and rate of C-alpha fluctuation. After exposure to the electric field, most of the hydrophobic tryptophan (TRP) residues turned to the hydrophilic surface, resulting the fluorescence red-shifted and quenched. Molecular docking indicated that the receptor binding domain of catechol in PPO was changed. PPO under electric field was MD simulated the first time, revealing the changing mechanism of the electric field itself on PPO, a binuclear copper enzyme, which has a metallic center. All these suggest that the low intensity DC electric field would be a promising option for enzymatic browning inhibition or even enzyme activity inactivation.
摘要：
在这项研究中,研究了低强度直流（DC）电场对蘑菇多酚氧化酶（PPO）的失活及其分子机理。在3V/cm下的实验中，5V/cm,7V/cm和9V/cm电场，PPO在不同的暴露时间后全部完全失活。低于1V/cm,残留活性为11.88%。失活动力学证实了Weibull模型。在1-7V/cm以下，n值接近约1.3的常数。通过荧光发射光谱和分子动力学（MD）模拟对3V/cm和5V/cm下PPO的结构进行分析，结果表明，随着回转半径的增加，其三级结构略有变化。较高的势能和C-α波动率。暴露于电场后,大部分疏水色氨酸（TRP）残基转向亲水表面，导致荧光红移和猝灭。分子对接表明PPO中儿茶酚的受体结合域发生了改变。首次对电场下的PPO进行了MD模拟，揭示电场本身对PPO的变化机制，一种双核铜酶，它有一个金属中心。所有这些表明，低强度直流电场将是酶促褐变抑制甚至酶活性失活的有希望的选择。
