An in vitro and in silico study to explore the response of catalase to 4-chlorophenol and their interacting mechanisms

Abstract

The present study conducted a novel strategy combining cellular and molecular methods to explore whether catalase (CAT) response is involved in 4-chlorophenol (4-CP) induced cytotoxicity and to investigate the detailed mechanism of CAT response to 4-CP. The results showed that the inhibition of CAT activity was not the primary cause of oxidative stress and cytotoxicity under 4-CP exposure. The decrease of intracellular CAT activity was contributed by the modulation of reactive oxygen species and the activity inhibition of CAT molecule. Isothermal titration calorimetry and molecular docking studies found that 4-CP binds to CAT with one binding site at the cavity between helical domain and threading arm majorly through van der Waals forces and hydrogen bonding. UV–vis absorption spectra showed that the binding unfolded the polypeptide chains of CAT and did not exhibit direct interruptions to heme groups around the active sites. Circular dichroism spectra found that the interaction caused secondary structure changes in CAT with a loss of α-helix content, which could be explained by the interaction of 4-CP with the residue HIS 62 in the binding site. Resonance light scattering spectra found that the aggregation state of CAT reduced under 4-CP exposure. These structural changes could influence the conformation around the active sites and then lead to the inhibition of molecular activity.