南国梨多酚氧化酶的研究

摘要

Fresh Nanguo pear as raw material, catechol as substrate, using spectrophotometric study of south-ern pear enzymatic characteristics of polyphenol oxidase. The results showed that:pH and temperature had a significant effect on fresh Nanguo pear PPO activity and the optimum pH was 6.8, fresh pear PPO optimum temperature was 40℃. Further study of the inhibitor of ascorbic acid, citric acid, sodium bisulfite, L-cys-teine, EDTA-2Na and various metal salts [CuSO4, CaCl2, Na2SO4, Al(NO3)3, CdCl2, HgCl2, MnCl2] effect of southern pear PPO, where 0.1 mmol/L of ascorbic acid on fresh pear PPO activity was significantly inhibited by up to 50 %. Nanguo pear PPO enzymatic catalytic substrate catechol reaction kinetics and the Michaelis-Menten equation height accord, R2=0.998, its kinetic equation 1/[V]=0.002/[S]+0.019, maximum reaction rate Vmax to 52.632 U/min,the Michaelis constant Km of 0.010 5 mol/L.%以新鲜南国梨果实为原料，邻苯二酚为底物，采用分光光度法研究南国梨多酚氧化酶的酶学特性。结果表明：pH和温度对新鲜南国梨PPO活性有明显的影响，最适pH为6.8，新鲜南国梨PPO最适温度为40℃。进一步研究了抑制剂抗坏血酸、柠檬酸、亚硫酸氢钠、L-半胱氨酸、EDTA-2Na和各种金属盐[CuSO4、CaCl2、Na2SO4、Al（NO3）3、CdCl2、HgCl2、MnCl2]对南国梨PPO的影响，其中0.1 mmol/L的抗坏血酸对新鲜南国梨PPO活性有明显抑制作用高达50%。南国梨PPO催化底物邻苯二酚的酶促反应动力学与米氏方程高度符合，R2=0.998，其动力学方程为1/[V]=0.002/[S]+0.019，最大反应速率Vmax为52.632 U/min，米氏常数Km为0.0105 mol/L。