DBD低温等离子体处理对多酚氧化酶活力及构象的影响

Effect of DBD Cold Plasma Treatment on Activity and Conformation of Polyphenol Oxidase

多酚氧化酶(PPO)会诱导酶促褐变,影响果蔬品质。为进一步阐释低温等离子体对PPO的作用机制,进而控制褐变,文中研究了介质阻挡放电(DBD)低温等离子体处理对PPO活力和构象的影响。结果表明:DBD低温等离子体处理时间达120和180 s时,几乎检测不到PPO的酶活力;DBD等离子体处理破坏了PPO的二级结构,α-螺旋占比从39.92%下降到9.47%,而β-折叠占比从15.32%上升到44.30%(处理180 s时)。荧光发射光谱显示,经处理后PPO的荧光强度从未处理的512.9下降到330.6,最大吸收峰有1.75 nm的红移。3D荧光光谱显示,等离子体破坏了PPO分子的多肽链骨架。原子力显微镜结果表明,DBD等离子体诱导PPO分子先聚集再解聚,从而影响酶活。DBD低温等离子体处理改变了PPO的二级、三级结构,促使蛋白氧化变性、酶活降低。文中研究为低温等离子体技术在果蔬褐变防控方面的应用提供了理论基础。

PPO(Polyphenol Oxidase)-induced enzymatic browning affects the quality of fruits and vegetables.To elucidate the mechanism of cold plasma on PPO and avoid browning,this study investigated the effect of cold plasma on PPO activity and conformation.The results showed that the enzyme activity of PPO could hardly be detected when the treatment time reached 120 s and 180 s.The active species of cold plasma destroyed the PPO secondary structures with the decrease ofα-helix(from 39.92%to 9.47%),and the increase ofβ-sheet(from 15.32%to 44.30%)(180 s).Fluorescence emission spectrum showed that after cold plasma treatment,the PPO fluorescence intensity decreased from 512.9 to 330.6,and the position of the maximum absorption peak showed a red shift of 1.75 nm.The 3D fluorescence spectra showed that the DBD plasma destroyed the polypeptide chain skeleton of the PPO molecule.Atomic force microscopy(AFM)showed that DBD plasma induced PPO molecule aggregation and then depolymerization,thus affecting the enzyme activity.In conclusion,cold plasma treatment changed the secondary and tertiary structures of PPO,and promoted the degeneration of protein oxidation and reduction of enzyme activity,providing theoretical support for the application of cold plasma in the inhibition of enzymatic browning and the maintenance of quality for fruits and vegetables.