Study On The Interaction Of Photolysis Products Of Tetracycline And Oxytetracycline With Soil Enzymes

Tetracycline and oxytetracycline are widely used in livestock and poultry breeding owing to their excellent bactericidal effect.However,due to excessive use,most of the antibiotics are not absorbed and discharged into surface water.Irrigation with surface water and fertilization with livestock manure lead to the widespread distribution of antibiotics in the soil,which inevitably causes soil ecological hazards.Transformation products of these antibiotic induced by environmental factors(such as light)could produce more serious environmental risks and ecological hazards than their parent chemicals.Soil enzymes play a key role in soil biochemical reactions,as well as in plant uptake of nutrients and the cycling of earth elements.Therefore,it is necessary to study the interaction between transformation products of antibiotic with soil enzymes.However,due to the complex composition of transformation products of antibiotic,the related research is insufficientIn this paper,tetracycline and oxytetracycline were used as model pollutants,and their transformation products were obtained by UV irradiation.Ultraviolet and fluorescence spectra were used to analyze the effects of two antibiotics and their photolysis Products on the skeleton structure and the microenvironment of a mino acid residues of urease and catalase.Molecular Operating Environment(MOE)was used to analyze the interaction details of two antibiotics and their photolysis Products with urease and catalase,as well as the main force types.The effects of two antibiotics and their photolysis Products on the enzymatic activity of urease and catalase were further analyzed by enzyme activity test.Compared with the parent compounds,the photolysis Products of both antibiotics exhibited stronger toxicity.This toxic effect not only changes the structure and microenvironment of urease and catalase,but also inhibits the catalytic activity of urease and catalase to some extent.The complex system formed by antibiotic parent compounds and their photolysis Products produces joint toxic effects,which are synergistic or additive.The specific results are as followsUltraviolet spectra showed that the photolysis Products of oxytetracycline had less effect on the skeleton structure of urease and catalase than their parent compounds,while effects of tetracycline and its photolysis Products on urease and catalase were slightly different.Synchrotron fluorescence spectra showed that tetracycline/oxytetracycline and its photolysis Products quenched the synchronous fluorescence 60 of urease,and their photolysis Products showed stronger quenching effect.The difference was that tetracycline/oxytetracycline and its photolysis Products showed the sensitization effect on catalase synchronization 60.The results showed that tetracycline/oxytetracycline and its photolysis Products changed the tryptophan residue microenvironment of urease and catalase.Three-dimensional fluorescence spectra showed that tetracycline/oxytetracycline and its photolysis Products showed strong fluorescence quenching effect on urease and catalase,and their photolysis Products showed stronger fluorescence quenching effect on urease and weaker quenching effect on catalase than their parent compounds.Enzymatic activity analysis showed that both tetracycline and oxytetracycline photolysates exhibited stronger inhibitory effects on urease and catalase.Molecular simulation studies show that the photolysis products of tetracycline and oxytetracycline may generate more interaction with urease and catalase than their parent compounds,and this enhancement is mainly hydrophobic in addition to hydrogen bonding interactions interaction.Therefore,we need to pay more attention to the photolysis Products of antibiotics in the environment due to their more ecological risks and hazards than the parent compounds of antibiotics.This study can not only provide a reference for risk assessment of soil pollution,but also provide a guidance for soil remediation.