Research On The Toxic Mechanisms Of SDBS Binding To Catalase And Trypsin

As a common synthetic anionic surfactant, Sodium dodecyl benzene sulfonate (SDBS) is widely used in the manufacture of detergent due to its experienced production process, low cost, easy to blister and strong detergency, and so on. With the continuous improvement of people’s life, more and more surfactant is released into the environment, which becomes an important environmental pollutant to cause damages to human health. Recently, reports on SDBS toxicity are mainly based on animal experiment. However, there is a lack of report concentrated on interactions between SDBS and proteins at the molecular level, and the binding mechanisms of anionic surfactants on protein has not been elucidated.Protein is formed by More than20kinds of amino acids with certain orders by dehydration condensation of the peptide bond, which is a biological macromolecule with more stable conformation. It is an important component of living organisms and the executor of life function. Pollutants in the environment could interact with proteins and affect biological function of proteins after they enter into bodies through respiratory system, digestive system and skin, which is a threat to human health. Therefore, the study on the interaction between SDBS and protein has become an important research topic in the field of the environment and health.In this paper, the binding mechanisms of SDBS on catalase (CAT) and trypsin were studied by spectroscopy (fluorescence spectroscopy, UV-vis absorption spectroscopy and circular dichroism), enzyme activity assay and molecular docking investigations. The results are as follows:1. Study on SDBS and CAT toxicity interactionUnder simulated physiological conditions, the binding mechanism of SDBS on catalase was explored using fluorescence spectroscopy, UV-vis absorption spectroscopy, circular dichroism spectroscopy and molecular docking studies. Results showed that SDBS could statically quench the fluorescence of catalase, bind into the catalytic site of catalase through hydrophobic effect (△H°>0、△S°>0), change the microenvironment surrounding Tyr into a more hydrophobic one. UV-vis absorption and CD results indicated that SDBS changed the secondary structure of catalase by loosening and destruction of catalase skeleton and increasing the hydrophobicity around Tyr residues, and resulted in the decreased activity of catalase according to the enzyme assay. MOE docking result showed that SDBS entered into the active site of catalase, hindered the path of the catalytic substrate (H2O2), and inhibited catalase activity.2. Study on SDBS and trypsin toxicity interactionSimilarly, the binding mechanism of SDBS on trypsin was explored. Results showed that the system of SDBS obvious quenched the fluorescence signal of trypsin, and the type of quenching is static quenching. SDBS bound into the catalytic site of trypsin through electrostatic effect (△H°<0△S°>0), and changed the microenvironment surrounding Tyr. UV-vis absorption and CD results indicated that SDBS changed the secondary structure of trypsin by loosening. As shown by enzyme activity assay, the enzyme activity of trypsin appeared significantly descent with the increase of SDBS. MOE docking result showed that SDBS entered into the active site of trypsin, hindered the path of the catalytic substrate, and inhibited catalase activity.The results of our study indicated that SDBS could interact with catalase and trypsin, and formed new compounds after entering into human bodies, resulted in structure and function changes of the protein.