title: Different modes of inhibition for organic acids on polyphenoloxidase.
abstract: 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.
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China. Electronic address: liuwei@ncu.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Xiong
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
authors.forename: Liqiang
authors.initials: L
authors.lastname: Zou
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
authors.forename: Junping
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, China.
authors.forename: Junzhen
authors.initials: J
authors.lastname: Zhong
mesh_terms: D004156:Catechol Oxidase / Q000737:chemistry*; D002934:Cinnamates / Q000737:chemistry*; D019343:Citric Acid / Q000737:chemistry*; D008293:Malates / Q000737:chemistry*; D008968:Molecular Conformation; D062105:Molecular Docking Simulation; D017433:Protein Structure, Secondary
chemical_list: D002934:Cinnamates; D008293:Malates; C029010:cinnamic acid; D019343:Citric Acid; C030298:malic acid; D004156:Catechol Oxidase
keywords: Conformation; Inhibitory mode; Molecular docking; Organic acid; Polyphenoloxidase; pH