Characterizing the binding interactions of sodium benzoate with lysozyme at the molecular level using multi-spectroscopy, ITC and modeling methods

• Sodium benzoate interacted with lysozyme and formed new complex. • Sodium benzoate statically quenched the intrinsic fluorescence of lysozyme. • The main forces for the interaction were hydrophobic force and hydrogen bond. • Sodium benzoate affected the molecular skeleton and function of lysozyme. In this paper, we mainly study the interaction mechanism between food additives and antioxidant enzymes. Spectral methods were used to study the effect of sodium benzoate on the structure and function of lysozyme at the molecular level. Multi-spectroscopic results showed that sodium benzoate statically quenched the intrinsic fluorescence of lysozyme, formed complexes with lysozyme, increased the polarity of the aromatic amino acid, effected the molecular skeleton of lysozyme and stretched the secondary structure. The molecular docking and isothermal titration calorimetry (ITC) results showed that sodium benzoate entered the depression of the surface of lysozyme molecule both through hydrophobic interaction and hydrogen bond. Sodium benzoate was linked to tryptophan (Trp-63) by a hydrogen bond with a bond length of 2.48 Å. Thermodynamic studies showed that the combination was spontaneous, as the values of the enthalpy change (ΔH) and the entropy change (ΔS) were calculated to be 12.558 kJmol −1 and 25 kJmol -1 k −1 , respectively. Enzyme activity determination showed that Sodium benzoate increased lysozyme activity by 22.31%. This study can provide experimental support for evaluating the edible safety of sodium benzoate.