The effects of sodium dodecyl sulphate on the behaviour of glucose oxidase enzyme

Glucose oxidase (GOx) is a flavoenzyme having applications in medical industries.GOx has found in the food industry for the glucose removal from dried eggs, for the removal of oxygen from fruit juices, for the production of gluconic acid, and as a source of hydrogen peroxide in food preservation [1]. Although it was observed that sodium dodecyl sulphate (SDS) can change the structure and function of protein, details of this interaction are not properly known yet. We treated GOx as dimer-active enzyme in the presence of various concentrations of SDS and seen that the enzyme become inactive at high concentration (25mM) of SDS. These experimental results are in agreement with recently published researches. To find a possible mechanism, simulation of the enzyme was performed in the presence of 25mM of SDS. MD simulations were carried out by GROMACS 5.0.4 with a GROMOS 43a1 forcefiled [2]. Parameters for flavin adenine dinucleotide (FAD) coezyme, which is the active center for GOx, were taken from the work of van den Berg et al [3]. RMSD values showed that the enzyme has an unstable conformation upon treatment with SDS. RMSF values demonstrated that the residue fluctuations for SDS-treated GOx were higher than those in native enzyme which such a situation is usually observed in the unstable structure. According to MD analysis, treatment of GOx with SDS may induce unfolding of the native dimeric enzyme, releasing FAD molecule from the enzyme and leading to a significant decrease in the enzymeactivity. To the best of our knowledge, this is the first study that bears detailed structural mechanism about the SDS effects on multimeric macromolecule.