Effects of mono and di(n-butyl) phthalate on superoxide dismutase

Di(n-butyl) phthalate (DBP) is a plasticizer used in the manufacture of several industrial and household articles. They get easily released to the environment and may cause adverse effects to living organisms. Effects of DBP and its metabolite monobutyl phthalate (MBP) on superoxide dismutase (SOD), an antioxidant enzyme, have been studied. When SOD was incubated with varying amount of DBP the activity of the enzyme was decreased proportionate to the concentration of the phthalates added. A similar result was observed with MBP also. These indicate that the DBP and MBP possess concentration dependent inhibitory effect on SOD. The mode of interaction of DBP and MBP has also been investigated using modeling and docking studies. The docking results showed that both DBP and MBP can bind in the active site of SOD and can make hydrogen bonds with the active site residue R143. This residue is crucial in the binding of reactive oxygen species (ROS) during its conversion to hydrogen peroxide and molecular oxygen. This may perhaps explain the inhibitory effect of DBP and MBP on SOD.