Antioxidants as stabilizers for His6-OPH: is this an unusual or regular role for them with enzymes?

The effect of 14 different antioxidants on the activity of a hexahistidine-tagged organophosphorus hydrolase (His6-OPH) has been studied in vitro. It has been found that antioxidants can have a positive, neutral or negative effect on the activity of His6-OPH in a native form or in the form of an enzyme-polyelectrolyte complex, while the enzyme itself does not affect their antioxidant activity. A significant stabilizing effect of a number of antioxidants on His6-OPH has been shown against its inhibiting with organic solvents (DMSO and isopropyl alcohol). The kinetics of the process has been studied. Based on molecular docking of all tested antioxidants to the surface of His6-OPH dimer, options of their localization have been identified. These data were used to explain the revealed stabilizing effect of the antioxidants on the enzyme as well as their negative influence on His6-OPH activity.