【摘要】 以新鲜菠菜叶为原料，提取菠菜叶过氧化物酶（peroxidase,POD），探讨最适pH、最适温度、反应活化能、K_m与V_max、热稳定性及热变性活化能等酶学特性，特别是热处理对其POD活性的影响及其相关动力学的研究．结果显示，以邻苯二胺作为POD的氢供体底物，H₂O₂为过氧化物底物，菠菜叶POD的最适pH为7.0，最适反应温度为30℃，反应活化能为29.49 kJ/mol．作为双底物反应，以邻苯二胺为底物时，该酶K_m值为1.976 mmol/L,V_max为120.48 U；以H₂O₂为底物时，该酶K_m值为3.573 mmol/L,V_max为133.33 U．热失活研究显示出一级失活动力学特征，Arrhenius作图得到一条斜率相当于168.47 kJ/mol的POD热变性活化能的直线．菠菜叶POD的热失活速度在55℃～60℃出现了跳跃式变化（速度常数k从-0.042变为-0.286）,60℃以后，菠菜叶POD对温度变化敏感，高温使得菠菜叶POD热不稳定部分的变性速度加快．更多还原

【Abstract】 Fresh spinach leaves were used as raw material to extract POD,and its enzymatic properties such as optimal pH,optimal temperature,catalytic activation energy,K_m and V_max,thermal stability and thermal denaturation activation energy were discussed.In particular,the influence of heat treatment on POD activity and its related kinetics were studied.The results showed that with o-phenylenediamine as the hydrogen donor substrate of POD,H₂O₂ as the peroxide substrate,the optimal pH was 7.0,the optimal reaction temperature was 30℃,and the activation energy of the catalytic reaction was 29.49 kJ/mol in spinach leaves POD.As a double substrate reaction,the K_m value of the enzyme was 1.976 mmol/L and V_max was 120.48 U when o-phenylenediamine was used as substrate.When H₂O₂ was used as substrate,the K_m value of the enzyme was 3.573 mmol/L and V_max was 133.33 U.The thermal inactivation study showed first-order inactivation kinetic characteristics,and Arrhenius plotted a straight line with a slope equivalent to 168.47 kJ/mol of POD enzyme thermal denaturation activation energy.There was a jump change （the velocity constant k being from-0.042 to-0.286） between 55℃and 60℃in the thermal inactivation rate of spinach leaves POD.After 60℃,POD in spinach leaves was sensitive to temperature change,and the denaturation rate of the thermally unstable part of POD in spinach leaves was accelerated by increasing temperature.更多还原