以儿茶素为底物研究水蜜桃多酚氧化酶的酶学特性

以水蜜桃中主要的酚类物质儿茶素为底物,研究水蜜桃多酚氧化酶的酶学特性。研究结果表明,该酶的最适反应温度为40℃、最适反应pH值为6.5;PPO的热稳定性结果表明,60℃以下时,水蜜桃中PPO较稳定,高于70℃,其稳定性迅速下降;pH值稳定性研究结果表明,酶在pH6.0以下及9.0以上时不稳定,pH为6.0～8.0时稳定;酶抑制学研究表明,谷胱甘肽和L-半胱氨酸在较低浓度时就能对此酶促反应产生较好的抑制作用,而氟化钠和氯化钠要在高浓度下才能对酶促氧化产生抑制作用,其抑制作用由强到弱的顺序为:L-Cys>GSH>NaF>NaCl。

Characterization of polyphenol oxidase from honey peach using(+)-catechin as substrate

Polyphenol oxidase(PPO) from honey peach had been characterized using(+)-catechin which was the major endogenous polyphenol in honey peach as substrate.The results indicated that the optimum temperature was 40 ℃.For thermostability studies,the enzyme was stable below 60 ℃ and the enzyme activity decreased significantly above 70 ℃.The results also showed that the optimum pH was 6.5 and the enzyme was stable in the pH range 6.0～8.0.The inhibition studies indicated that L-cysteine and glutathione were more effective for the inhibition of peach PPO,while NaF and NaCl inhibited moderately,especially NaCl.In conclusion,the inhibition effects on the enzyme activity were as follow:L-Cys>GSH>NaF>NaCl.