The effect of pH on the activity, thermokinetics and inhibition of polyphenol oxidase from peach
The effect of pH on the activity, thermokinetics and inhibition of polyphenol oxidase from peach
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DOI：
10.1007/s13197-015-1822-3
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发表时间：
2015-04
期刊：
影响因子：
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通讯作者：
Liang Liu;Shao-qian Cao;X. Qi;Zhengfeng Yang
中科院分区：
文献类型：
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作者：
Liang Liu;Shao-qian Cao;X. Qi;Zhengfeng Yang
本研究重点研究了pH值对以(+)-儿茶素为底物的蜜露桃果肉中多酚氧化酶(PPO)的活性、热动力学和抑制作用的影响。 PPO 活性的最适 pH 值约为 6.5–7.0，最适温度取决于 pH 值，pH 6.8 时为 40 °C，pH 4.0 时为 30 °C。在 4°C 储存期间，该酶在 6.0–8.0 的 pH 范围内保持稳定。然而，PPO 的热动力学参数（D、z、k、Ea）表明，在热处理过程中，该酶在 pH 6.8 下比在 pH 6.0 和 pH8.0 下稳定得多。此外，结果还表明，与其他 pH 值相比，该酶在 pH 6.8 时对温度变化更敏感。抑制研究表明，L-半胱氨酸和谷胱甘肽对该酶的抑制非常有效，而 NaF 在 pH 6.8 时具有中等抑制作用。然而，这些抑制剂的抑制能力具有pH依赖性，酸性介质可以大大提高NaF对桃浆PPO的抑制能力。
This study focused on the effect of pH on the activity, thermokinetics and inhibition of polyphenol oxidase (PPO) from honeydew peach pulp with (+)-catechin as the substrate. The optimum pH for the PPO activity was around 6.5–7.0, and the optimum temperature was pH dependent and it was 40 °C at pH 6.8 while 30 °C at pH 4.0. The enzyme was stable in the pH range of 6.0–8.0 during the storage at 4 °C. However, the thermokinetics parameters (D, z, k, Ea) of PPO suggested that the enzyme was much more stable at pH 6.8 than at pH 6.0 and pH8.0 during the thermal treatments. Moreover, the results also indicated that the enzyme was more sensitive to the change of temperature at pH 6.8 than at the others pH. The inhibition study indicated that L-cysteine and glutathione were highly effective for the inhibition of the enzyme while NaF inhibited moderately at pH 6.8. However, the inhibition abilities of those inhibitors were pH dependent, and acidic medium could greatly increase the inhibition ability of NaF for peach pulp PPO.