脉冲强光对多酚氧化酶活性及结构特性的影响

为探究脉冲强光(IPL)对果蔬内源酶活性的抑制效果及相关机理,采用分光光度法研究了IPL处理对多酚氧化酶(PPO)活性的影响,并通过ANS荧光探针法、内源荧光光谱法、凝胶电泳及圆二色(CD)光谱等方法探讨了不同能量IPL处理对PPO结构特性的影响。结果表明,PPO活性随着IPL单次脉冲能量、脉冲次数的增加及脉冲板间距的减小而降低。IPL处理后,PPO表面疏水性及游离巯基含量上升,色氨酸荧光强度下降,最佳发射波长红移,α-螺旋含量下降,β型结构含量上升。同时,凝胶电泳结果显示,PPO蛋白氧化降解。综上,IPL处理可改变PPO二级和三级结构,促使蛋白氧化变性,酶活性下降。本研究结果为IPL技术在抑制食品中内源酶活性及其相关机理的研究提供了一定的理论依据。

Effect of Intense Pulsed Light on Polyphenol Oxidase Activity and Structure Properties

To explore the inhibitory effect and related inactivation mechanism of intense pulsed light (IPL) on the endogenous enzyme activity in fruits and vegetables, the effect of IPL treatment on the activity of polyphenol oxidase (PPO) was investigated by spectrophotometry, and the structure properties of PPO under different IPL treatment was also analyzed by ANS fluorescent probe, intrinsic ?uorescence spectroscopy, gel electrophoresis and circular dichroism (CD) spectra. The results showed that PPO activity decreased with the increase of single pulsed energy, pulse times and the reduction of pulse distance. After IPL treatment, the optimal emission wavelength of PPO was red-shifted, and the surface hydrophobicity, the content of free sulfhydryl and β-structure were increased, while the intrinsic fluorescence intensity and the content of α-helix were decreased. Meanwhile, the electrophoresis pattern showed that oxidative degradation of PPO protein occurred. The above results indicated IPL treatment could change the secondary and tertiary structure of PPO, promote protein oxidative degeneration, and decrease the enzyme activity. This study provides a theoretical basis for the study of IPL technology in inhibiting endogenous enzyme activity and reveals related inactivation mechanisms.