青蒿多酚氧化酶的酶学特性研究

Enzymatic Properties of Polyphenol Oxidase in Artemisia carvifolia

以新鲜青蒿为材料,考察不同温度、pH值、底物浓度、激活剂、抑制剂对青篙多酚氧化酶（polyphenol oxidase,PPO）活性的影响。结果表明:温度和pH值对酶活性的影响均存在一个最适值,分别为40℃和6.8;在一定底物浓度范围内,酶促反应速率随底物浓度的增加而增大,其米氏常数（Km）为0.0154mol/L,最大反应速率（Vmax）为125U/min;MgCl2、SDS对青蒿PPO活性有一定激活作用,当MgCl2浓度为0.9mmol/L、SDS浓度为8mmol/L时,青蒿PPO活性分别高出对照组30.3%和45.3%;当VC质量浓度为0.03g/L、柠檬酸质量浓度为1.2g/L、PVP质量浓度为20g/L时抑制率分别为70.4%、83.7%、77.6%;NaHS03在0.010.08mmol/L的浓度范围内对青蒿PPO抑制作用缓慢上升。

The study was performed to explore the effects of temperature,pH,substrate concentration,activator,and inhibitor on PPO activity of Artemisia apiacea.Experimental results showed that the optimal pH and temperature for PPO activity were 40 °C and 6.8,respectively.The Michaelis constant(Km) was 0.015 4 mol/L and Vmax was 125 U/min,which was increased along with an increase in substrate concentration in a certain range.As compared with the control,MgCI2 and SDS activated PPO activity by 30.3%and 45.3%when added at a concentration of 0.9 and 8 mmol/L,respectively.VC,citric acid and PVP inhibited the enzyme activity by 70.4%,83.7%and 77.6%when used at a concentration of 0.03,1.2 and20g/L,respectively.The inhibition of NaHSO3 on PPO activity rose slowly with increasing concentration from 0.01 to 0.08 mmol/L.