芡实多酚氧化酶的酶学性质

Enzymatic Properties of Polyphenol Oxidase from Gordon Euryale Seed

以紫花苏芡和紫花刺芡种仁为原料制备粗酶液,研究多酚氧化酶(PPO)酶学性质。结果表明:紫花苏芡和紫花刺芡PPO最适作用条件均为温度45℃和pH 6.5;铁离子和亚铁离子对芡实PPO酶活性具有较强的促进作用,钙离子低质量浓度时抑制酶活性,较高质量浓度时使酶活性反弹,没有表现出明显的激活作用,铝离子有一定的促进作用,铜离子低质量浓度对酶活性有促进作用,高质量浓度有抑制作用;有机酸柠檬酸、草酸、抗坏血酸和EDTA、还原剂亚硫酸氢钠和硫代硫酸钠对紫花苏芡和紫花刺芡PPO酶活性都有抑制作用。

Dehulled kernels of two varieties ofEuryaleferox Slisb, Zihua Suqian and Zihua Ciqian from respectively Suzhou and Hongze, Jiangsu province of China, were used as raw materials to prepare and characterize crude polyphnol oxidase （PPO） extract. The results showed that PPO enzymes from both verities of gordon euryale had the highest activity at 45 ℃ and pH 6.5. Ferric and ferrous ions were highly effective in promoting PPO activity. Calcium inhibited PPO activity at low concentrations, but not at high concentrations. Aluminum ion and copper ion at low concentrations activated PPO activity, while high levels of copper ions inhibited it. PPOs were inhibited by organic acids, like citric acid, oxalic acid, ascorbic acid, and ethylenediaminetetraacetic acid （EDTA）, and the reductants sodium bisulfate and sodium thiosulfate.