菠菜叶过氧化物酶的热失活及其动力学特性OA

Fresh spinach leaves were used as raw material to extract POD,and its enzymatic properties such as optimal pH,optimal temperature,catalytic activation energy,Km and Vmax,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 Km value of the enzyme was 1.976 mmol/L and Vmax was 120.48 U when o-phenylenediamine was used as substrate.When H2O2 was used as substrate,the Km value of the enzyme was 3.573 mmol/L and Vmax 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.