Weikang Tang,Ling Zhang,Qinfei Chen,Mengqi Han,Chan Chen,Wenbin Liu
Tyrosinase is pivotal for melanin formation . Measuring monophenolase activity is of great importance for both fundamental research and industrial applications. For the first time, a backpropagation (BP) artificial neural network with three-dimensional fluorescence spectroscopy was applied for the real-time determination of tyrosinase monophenolase activity. Principal component analysis (PCA) was utilized for the dimension reduction of three-dimensional fluorescence data. The four principal components served as inputs for the neural network. Network parameters were optimized using a genetic algorithm (GA). BP learning algorithm was applied to train the network model to determine tyrosine levels in a binary mixture containing tyrosine and L -DOPA without any chemical separation. The time course of tyrosine consumption by monophenolase was determined to calculate the initial velocity of the enzymatic reaction. The limit of detection of the monophenolase assay was 0.0615 U·mL −1 . This combined strategy of PCA, GAs, and BP artificial neural networks for three-dimensional fluorescence spectroscopy was efficient for the real-time and in-situ determination of monophenolase activity in a cascade reaction.
Gui-Li Huang,Tian-Tian Liu,Jia-Jia Ma,Ling-Xiang Sun,Si-Yao Sui,Xin-Yao Quan,Yu-Ning Wang
The harvested loquat fruits are prone to browning, leading to a decline in fruit quality. Inhibiting activity of polyphenol oxidase (PPO) is an important way to prevent browning. In this study, we evaluated the inhibitory impact of oligomeric procyanidins (OPC) on hydroxylation of monophenol and oxidation of o-diphenol catalyzed by PPO and effect of OPC on loquat fruits storage . The obtained results revealed that OPC could attenuate the activity of monophenolase and diphenolase. For monophenolase activity, the inhibition rate was observed to be dose-dependent with an IC 50 of 11.6 ± 3.4 μg/mL for the steady-state rate. For diphenolase activity, OPC inhibited PPO activity ( IC 50 = 15.75 ± 2.1 μg/mL) with a reversible and competitive mechanism and quenched fluorescence of PPO by forming OPC-PPO complex with one binding site in a static procedure. In addition, the data obtained from storage assays revealed that OPC could enhance the quality of harvested loquat fruits by attenuating the PPO activity, augmenting the content of total phenolics and flavonoids , and simultaneously delaying the browning of loquats. In this research, we identified a potent PPO inhibitor and expanded its potential as a food preservative.
危险品化学品经营许可证（带存储）