title: Effect of ultrasound combined with malic acid on the activity and conformation of mushroom (Agaricus bisporus) polyphenoloxidase.
abstract: Polyphenoloxidase (PPO) plays an important role in the browning of vegetables, fruits and edible fungi. The effects of ultrasound, malic acid, and their combination on the activity and conformation of mushroom (Agaricus bisporus) PPO were studied. The activity of PPO decreased gradually with the increasing of malic acid concentrations (5-60mM). Neither medium concentrations (10, 20, 30mM) malic acid nor individual ultrasound (25kHz, 55.48W/cm(2)) treatment could remarkably inactivate PPO. However, the inactivation during their combination was more significant than the sum of ultrasound inactivation and malic acid inactivation. The inactivation kinetics of PPO followed a first-order kinetics under the combination of ultrasound and malic acid. The conformation of combination treated PPO was changed, which was reflected in the decrease of α-helix, increase of β-sheet contents and disruption of the tertiary structure. Results of molecular microstructure showed that ultrasound broke large molecular groups of PPO into small ones. Moreover, combined treatment disrupted the microstructure of PPO and molecules were connected together.
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: 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
authors.affiliation: State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang, 330047, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
mesh_terms: D000364:Agaricus / Q000201:enzymology*; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005656:Fungal Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008293:Malates / Q000494:pharmacology; D018625:Microscopy, Atomic Force; D011487:Protein Conformation / Q000187:drug effects; D017433:Protein Structure, Secondary / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects; D014465:Ultrasonics
chemical_list: D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D008293:Malates; C030298:malic acid; D004156:Catechol Oxidase
keywords: Conformation; Inactivation; Malic acid; Microstructure; Polyphenoloxidase; Ultrasound