Glutathione peroxidase 6 from Arabidopsis thaliana as potential biomarker for plants exposure assessment to di-(2-ethylhexyl) phthalate.

As a most abundant plasticizer, Di-(2-ethylhexyl) phthalate (DEHP) has been widely used in agriculture with an associated potential toxicity to many species including plants via the production of the excessive reactive oxygen species (ROS). However, the potential toxic mechanisms of the plasticizer DEHP-induced oxidative damage to plants remain unknown. The antioxidant enzyme glutathione peroxidase has been suggested as biomarkers to reflect over excessive oxidative stress. In this study, the effect of DEHP on AtGPX6 was evaluated by multi-spectroscopic techniques and molecular docking method. The fluorescence intensity of AtGPX6 was reduced by the static quenching mechanism upon the addition of DEHP. The predominant forces in complex formation was mainly impelled by hydrogen bonding and Van der Waals forces based on the negative ΔH and ΔS, which was in accordance with the molecular docking results. In addition, the secondary structural changes resulted from the complex formation were investigated in presence of different amounts of DEHP by the combination of fluorescence, UV-vis absorption and Circular dichroism spectra, which revealed the loosening and unfolding of the framework of AtGPX6 accompanied with the enhancement of the hydrophilicity around the tryptophan residues. The exploration of the interaction mechanism of DEHP with AtGPX6 at molecular level would help to evaluate the toxicity of the plasticizers and forecast the related adverse effects on plants.