Rational Design And Screening Research Of Novel Lead Compound Based On Structure Of Target Enzyme Polyphenol Oxidase

Polyphenol oxidase(PPO) is a kind of encoded by the nuclear complex copper REDOX enzyme. PPO is catalytic oxidation of phenol. PPO widely exist in plants, the human body, animals, microorganisms and other organisms in the nature. PPO is one of the important enzymes browning of fruit and vegetable. The fruit and vegetable browning caused great economic loss. Therefore, the development of efficient new PPO inhibitors is of great importance.With computer aided drug design, molecular biology and enzymology rapid development in many areas, such as the reasonable drug molecular design has become an important way for new drug research and development. In this topic research, we accorded to the structural characteristics of PPO, then integrated use of computer aided drug design, determination of biological activity and organic synthesis technology based on PPO structure characteristics of the new inhibitor to virtual screening lead compounds with reasonable design, chemical synthesis and biological activity determination. The specific is as follows:Fristly, the virtual screening of lead compounds: first of all, as a result of the lotus root PPO crystal structure is not parsing, so first we used sweet potato PPO as templates, through the SWISS- MODEL homologous MODEL built by lotus root PPO protein threedimensional structure. And then we accorded to the inhibitors and the mechanism of action of lotus root between PPO activity sites for analysis and research, the Suflex- Dock and GOLD- Wizard two docking methods were determined for virtual screening. 24 Potential active compounds were selected from more than 70000 commercial database based on combining conformation and binding force between small molecules ligand and protein. We bought 24 candidate compounds from Specs company, and determination of biological activity.Secondly, biological activity determination of aspects: we determine the biological activity of PPO by measuring the absorbance at 410 nm that used UV. We determination of 24 candidate compound enzyme level of biological activity. The experimental results showed that the 18 compounds activity is best, IC50 is 0.14 mg/mL, Ascorbic acid that has commercialization IC50 is 0.12 mg/m L, 18 Compounds and reference to the structure( phenylthiourea) have similar docking conformation and function mechanism. Therefore, we will use 18 compounds as lead compounds in the further study of structure design.Thirdly, the optimized design of lead compounds: according to the mechanism of action between PPO activity sites and inhibitors and with reference to the structure of the molecular structure characteristics, the structure of 18 compounds was optimized design, eventually the optimized target structure is N- substituted phenyl- hydrazides thiosemicarbazide. 21 Compounds were synthetized by one-pot reaction, and structure characterization of target compounds of was made by IR and 1HNMR. Target compounds were for biological activity used same method. The experimental results show that A2 has best biological activity, IC50 is 0.015 mg/mL, its inhibition rate increased by 89.29 % than lead compounds.Fourthly, quantitative Structure- Activity Relationship: we conducted QSAR analysis between the structure of the 21 target compounds and activity data of inhibition of PPO enzyme, and a significant correlation QSAR models were acquired: q2=0.607, r2=0.997, N=2, SEE=0.045, F=304.588. Model shows that introduction of bulky groups on R2 substituent and introduction of polar atoms groups on R1 substituent will improve activity. The model will provide a theoretical basis for the further structural designation.