Theoretical Study On The Degradation Mechanism Of Polyvinyl Alcohol And Polyethylene Glycol In The Pseudomonas Hydrolase

Plastic products have become an indispensable material in domestic life and varied industries,but methods to treat plastics is unsound,and a large number of plastic materials cannot biodegrade easily,which cause a great threat to our environment.Modifications the existing enzymes can improve the catalytic function of the enzymes and the biodegradability of the plastics,which can effectively alleviate the threats caused by the discharge of a large number of plastic into the environment.It can also increase the efficiency of plastic products in recycling and reuse.Computer simulation can provide guidance for traditional experiments and advice on enzyme modification by theoretical calculations,and reduce the time and economic cost of traditional experiments.In addition,the computational simulation can describe the reaction mechanism which is hard to obtain at atomic level,enhance the understanding of the enzymatic reaction mechanism,and lead to a better understanding and utilization of enzymes.Molecular dynamics(MD)and the method of combination quantum mechanics with molecular mechanics(QM/MM)are two important means to simulate biomolecules by computer,and it is also a powerful tool for enzyme research at present.In the present studies,the interaction mechanism of Pseudomonas hydrolase on polyvinyl alcohol and polyethylene glycol was studied by means of MD,QM/MM,and the role of important amino acids in the enzyme was also discussed,also structural details of enzyme degradation and oxidation of polyvinyl alcohol were described from a microscopic point of view.By investigating of the details of the enzyme reaction mechanism,it is speculated that the hydrogen bond in the enzyme environment may be the main factor for the degradation of plastics in the environment..1.The degradation mechanism of oxidized polyvinyl alcohol under Pseudomonas hydrolasePolyvinyl alcohol is a kind of plastics widely used in industries,and it is also a kind of material which has been studied relatively early.Here,acetylacetone as the dimer of oxidized polyvinyl alcohol was used to study the binding process of Pseudomonas hydrolase and the polyvinyl alcohol,and the catalytic process was studied by QM/MM.The results show that Glul2 and Trp121 can promote the substrate-enzyme binding process in the binding stage to prepare for the subsequent catalytic process.The hydroen bond network formed between the residue Gly65.Ser66,Va167 and the substrate in the reaction stage can stabilize the eneragy of the substrate in the reaction process and make the reaction take place.The fracture of carbon-carbon bond in the reaction is the rate determining step of the reaction.which has an energy barrier of 10.97 kcal/mol.The electrostatic effect of Glu198 is an important role in promotin,g the reaction.2.The mechanism of the interaction between polyethylene glycol and Pseudomonas hydrolasePolyethylene glycol is a kind of water-soluble plastics which have been widely used.The study of polyethylene glycol has been carried out earlier,but there is still no suitable degradation method.The dimer of polyethylene glycol(PEG)was used to study the behavior of PEG under the action of P.seucdomonas hydrolase by means of molecular dynamics and quantum mechanics,in order to have a better understanding of the behavior of PEG.The results indicate that PEG could bind to P.seudomonas hvdrolase stably,but the chain could not break under the action of Pseudomonas hydrolase.Reside Tyr270 plays an important role in the interaction between PEG and P.seudomonas hydrolase.Because PEG lacks the structure of forming hydrogen bonds with the enzyme env ironment,the deradation reaction of the PEG is difficult to occur.