Towards Al-induced manganese-containing superoxide dismutase inactivation and conformational changes: an integrating study with docking simulations.

Superoxide dismutase (SOD, EC 1.15.1.1) plays an important antioxidant defense role in skins exposed to oxygen. We studied the inhibitory effects of Al(3+) on the activity and conformation of manganese-containing SOD (Mn-SOD). Mn-SOD was significantly inactivated by Al(3+) in a dose-dependent manner. The kinetic studies showed that Al(3+) inactivated Mn-SOD follows the first-order reaction. Al(3+) increased the degree of secondary structure of Mn-SOD and also disrupted the tertiary structure of Mn-SOD, which directly resulted in enzyme inactivation. We further simulated the docking between Mn-SOD and Al(3+) (binding energy for Dock 6.3: -14.07 kcal/mol) and suggested that ASP152 and GLU157 residues were predicted to interact with Al(3+), which are not located in the Mn-contained active site. Our results provide insight into the inactivation of Mn-SOD during unfolding in the presence of Al(3+) and allow us to describe a ligand binding via inhibition kinetics combined with the computational prediction.