Rational Design Of Novel Inhibitors Based On3HNR And CYP51from Magnaporthe Grisea

Rice blast disease, caused by the fungus Magnaporthe grisea, is one of the most important diseases of rice. The subject of development commercially important fungicides which are used to prevent blast disease in rice plants has get more and more attention from domestic and overseas.Trihydroxynaphthalene reductase (3HNR), which catalyzes the conversion of trihydroxynaphthalene to vermelone in the melanin biosynthetic pathway, has proven to be a valuable target for development of rice blast fungicides. Fungicides, such as tricyclazole, inhibiting3HNR of Magnaporthe grisea, are defined as melanin biosynthesis inhibitor-reductase (MBI-Rs). Cytochrome P45014a-sterol demethylase (CYP51) is a essential enzyme in sterol biosynthesis in eukaryotes and well known as a drug target for microbial pathogenic infections.14a-sterol demethylase inhibitors (DMIs) block demethylation of sterol precursors at the C14-position,which is the obligatory step in sterol biosynthesis in eukaryotes. Some of the DMIs, such as azoles, have also been used to prevent blast disease in rice plants.DMIs have high bactericidal efficiency but also have high resistance. As non-direct fungi-toxic chemicals, MBI-R have less efficacy than DMIs, but also have less resistance than DMIs. So it is an impotrtant project to develop novel inhibitors which have high efficiency and low resistance. One solution of the problam is to find a kind of inhibitors acting on3HNR and CYP51at the same time.In this thesis the structure information of CYP51, the interaction mechanism between ligands (MBI-Rs and DMIs) and active site of receptor (3HNR and CYP51) were systemic researched by molecular simulation, gene engineering, spectroscopic analysis. Based on above information structure-based rational design and screen for novel and effective lead structure of inhibitors were performed. The present thesis is organized as follows:Firstly,3D-structure of14a-sterol demethylase of Magnaporthe grisea (CYP51) was constructed by homology modelling and molecular dynamics simulations.Secondly,base on the information of interaction mechanism between ligands (MBI-Rs and DMIs) and receptors(3HNR and CYP51), we use the strategy that combination of restrictive docking and flexible docking to virtual screening for novel inhibitors of3HNR and CYP51.Finally forty-four hits compounds were screening out.Thirdly, we carry out biological tests on thalli and enzyme level and then obtain three lead compounds which can be optimize in the future.