Study On The Mechanism Of Surfactant To Degradation Of Phenol By Laccase:Molecular Docking And Molecular Dynamics

Phenolic compounds widely exist in the wastewater discharged from factory,agriculture and human,which are toxic and chronically threat to human and animal health.They belong to carcinogens that cause damage to red blood cells and liver even at low concentration.Therefore,it is necessary to reduce the content of phenolic compounds up to a specified value via a series of sewage treatment technologies before the wastewater is discharged into the natural water.Phenolic contaminates could be transformed and degraded by ozone,absorption,extraction,photocatalytic degradation,biodegradation,Fenton oxidation and membrane separation.Microbial or enzymatic degradation has many advantages,such as low cost,complete mineralization,no secondary pollution,environmental protection,and etc.There are many studies have reported that microorganisms or enzymes was applied to remove phenolic compounds from wastewater.Since phenol belongs to hydrophobic organic pollutant,the efficiency of enzymatic degradation of phenol in wastewater is not satisfactory.The addition of surfactants led to significant increase of the efficiency of enzymatic degradation.Many studies have also shown that surfactants reduced the toxicity of phenol to enzymes.However,in many studies,the effects of surfactants on the interactions of enzyme and phenol have not been investigated at the molecular level.Thus,the corresponding theoretical research is necessary to provide a deeper theoretical basis.In this paper,the effects of two different types of surfactants on the degradation of phenol by laccase were investigated by molecular docking and molecular dynamics simulation.Firstly,the binding model of laccase and phenol was studied by molecular docking.The optimal binding model of laccase-phenol complex was determined by scoring function.Then the interactions between laccase and phenol were analyzed by software in detail.It was found that the phenolic hydroxyl group played a key role in the formation of hydrogen bonds.The influences of Triton X-100 and rhamnolipid on the laccase-phenol complex were studied by molecular dynamics simulation.The results showed that phenol contacted with the active site of laccase by hydrogen bonding and van der Waals interaction in aqueous solution in order to maintain its stability.The presence of Triton X-100 or rhamnolipid resulted in significant changes of the enzymatic conformation.At the same time,the hydrophobic group of the surfactant was in contact with the outer surface of laccase.These changes result in the decrease of the binding energy of phenol to laccase and also changed the number of hydrogen bonds between laccase and phenol or water molecules.The migration behavior of water molecules within the hydration layer was also inevitably affected.Therefore,the amphoteric Triton X-100 or rhamnolipid may affect the laccase's ability to degrade phenol by regulating their interactions and the water environment.This study provides a molecular level of understanding of the role of surfactants in biological systems.