Wen Yi-Ting, Liang Yu-Qin, Chai Wei-Ming, Wei Qi-Ming, Yu Zi-Yi, Wang Lin-Jun
College of Life Science and Key Laboratory of Functional Small Organic Molecule, Ministry of Education, Jiangxi Normal University, Nanchang, China.
J Food Biochem. 2021 Dec;45(12):e13995. doi: 10.1111/jfbc.13995. Epub 2021 Nov 3.
Tyrosinase (polyphenol oxidase) is the key enzyme of enzymatic browning in fruits and vegetables. In this research, the impact of ascorbic acid on tyrosinase and its anti-browning effect on fresh-cut Fuji apple were investigated. Ascorbic acid had a dual effect on tyrosinase with a half inhibitory concentration (IC ) of 13.40 ± 0.05 µM. Fluorescence assay demonstrated that ascorbic acid interacted with tyrosinase in a dynamic contaction caused by Förster's resonance energy transfer (FRET) and induced a conformational change of the enzyme. Thermodynamic analysis, copper interaction, and molecular docking further confirmed that ascorbic acid could chelate the copper ions located in active center and interact with amino acid residues of tyrosinase via hydrophobic interaction. In addition, ascorbic acid prevented the browning of fresh-cut apples by increasing APX activity and inhibiting PPO and POD activities which reduce the oxidation of total phenolics and flavonoids. PRACTICAL APPLICATIONS: The present study demonstrated that ascorbic acid had a strong inhibitory activity against tyrosinase (IC = 13.40 ± 0.05 µM) and anti-browning activity against fresh-cut Fuji apple. It could delay the browning degree of apple juice, increase APX activity, inhibit PPO and POD activities, and reduce the oxidation of total phenolics and flavonoids. These findings provided a basis for the feasible application of ascorbic acid on the preservation of fruits.
酪氨酸酶（多酚氧化酶）是水果和蔬菜酶促褐变的关键酶。本研究考察了抗坏血酸对酪氨酸酶的影响及其对鲜切富士苹果的抗褐变作用。抗坏血酸对酪氨酸酶具有双重作用，其半抑制浓度（IC₅₀）为13.40±0.05 μM。荧光分析表明，抗坏血酸与酪氨酸酶通过Förster共振能量转移（FRET）发生动态相互作用，并诱导酶的构象变化。热力学分析、铜离子相互作用及分子对接进一步证实，抗坏血酸可螯合位于活性中心的铜离子，并通过疏水相互作用与酪氨酸酶的氨基酸残基相互作用。此外，抗坏血酸通过提高APX活性、抑制PPO和POD活性来防止鲜切苹果褐变，从而减少总酚类和黄酮类的氧化。实际应用：本研究表明，抗坏血酸对酪氨酸酶具有较强的抑制活性（IC₅₀ = 13.40±0.05 μM），对鲜切富士苹果具有抗褐变活性。它可以延缓苹果汁的褐变程度，提高APX活性，抑制PPO和POD活性，并减少总酚类和黄酮类的氧化。这些发现为抗坏血酸在水果保鲜中的可行应用提供了依据。
