Molecular Dynamics Investigation On The Action Mechanism Of Glucose Oxidase With ?-D-glucose

Glucose oxidase(GOx)is an important biocatalyst in many microorganisms and insects,which is widely used in food industry,clinical chemistry and other industries.Glucose oxidase is mainly purified from Aspergillus niger and Penicillium amagasakiense for biotechnological applications.Glucose oxidase consists of two identical subunits,each of which comprises about 580 amino acid residues and binds a noncovalent flavin adenine dinucleotide cofactor FAD.Glucose oxidases catalyses the oxidation of ?-D-glucose to ?-gluconolactone and the reduction of molecular oxygen to hydrogen peroxide.The reaction process can be divided into the reductive half-reaction of FAD and the oxidative half-reaction of FADH2.In the reductive half reaction,two hydrogen atoms are transferred from the beta-glucose molecule to FAD,while ?-gluconolactone is subjected to non-enzymatic hydrolysis to produce gluconic acid.In the oxidative half reaction,FADH2 is reoxidized back to the original state by molecular oxygen and hydrogen peroxide is generated.The enzyme activity of GOx for ?-D-glucose is about 160 times higher than that for ?-D-glucose.Therefore,the phenomenon has raised concern.In this thesis,the crystal structures of glucose oxidase from Penicillium amagasakiense and ?-D-glucose were obtained from PDB database.Molecular dynamics simulations were performed using Amber16 software.The results show that only Glu416,His520 and His563 are present within close proximity of the reaction center and a strong hydrogen bond between His563N?2 and Glu416O? can be observed.So,we focus on the analysis of those residues.We have found that the C1-hydroxyl of ?-D-glucose is inclined to transfer hydrogen to His520N?2.At the same time,the C1 carbon of ?-D-glucose has a tendency to transfer hydrogen to FAD N5.Meanwhile,we noticed that the probabilities of forming a hydrogen bond between His563H?2 and Glu416O?1 or Glu416O?2 are 0.55 and 0.44,respectively.However,the probabilities of forming a hydrogen bond between His563H?2 and Glu416O?1 or Glu416O?2 for enzyme-substrate complex are 0.235 and 0.745,respectively.The data show that Glu416O?2 prefers to form hydrogen bond with His563H?2 in the enzyme-substrate complex,.In the thesis,molecular dynamics simulations of the action mechanism of GOxgluocose complex are investigated.Analyses of the changes of GOx active pockets,peptide reaction center,cofactor FAD and ?-D-glucose are performed to deepen the understanding of action mechanism of GOx and ?-D-glucose.