State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
Food Chem. 2016 May 15;199:439-46. doi: 10.1016/j.foodchem.2015.12.034. Epub 2015 Dec 9.
It is still unclear whether the inhibitory effect of organic acid on polyphenoloxidase (PPO) is due to the reversible inhibition or decrease of pH. In this study, cinnamic acid, citric acid and malic acid inhibited PPO in different modes. Results showed that the inhibition by cinnamic acid resulted from reversible inhibition, while the decrease of pH was the main cause for citric acid and malic acid. The kinetic results showed that cinnamic acid reversibly inhibited PPO in a mixed-type manner. Fluorescence emission spectra indicated that cinnamic acid might interact with PPO and quench its intrinsic fluorescence, while the decrease of the fluorescence intensity induced by citric acid or malic acid was due to the acid-pH. Cinnamic acid bound to PPO and induced the rearrangement of secondary structure. Molecular docking result revealed cinnamic acid inserted into the hydrophobic cavity of PPO by forming π-π stacking.
目前尚不清楚有机酸对多酚氧化酶（PPO）的抑制作用是由于可逆抑制还是 pH 值降低。在这项研究中，肉桂酸、柠檬酸和苹果酸以不同的方式抑制了 PPO。结果表明，肉桂酸的抑制作用源于可逆抑制，而柠檬酸和苹果酸则主要是由于 pH 值降低所致。动力学结果表明，肉桂酸以混合抑制的方式可逆地抑制 PPO。荧光发射光谱表明，肉桂酸可能与 PPO 相互作用并猝灭其内在荧光，而柠檬酸或苹果酸引起的荧光强度降低则是由于酸-pH 值。肉桂酸与 PPO 结合并诱导其二级结构重排。分子对接结果表明，肉桂酸通过形成π-π 堆积插入到 PPO 的疏水性腔中。
