A Novel 65-Mer Peptide Imitates the Synergism of Superoxide Dismutase and Glutathione Peroxidase

Reactive oxygen species (ROS) are involved in cell growth, differentiation, and death. Excessive amounts of ROS (e.g., O2−, H2O2, and HO) play a role in aging as well as in many human diseases. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) are critical antioxidant enzymes in living organisms. SOD catalyzes the dismutation of O2− to H2O2, and GPx catalyzes the reduction of H2O2 and other harmful peroxides by glutathione (GSH). They not only function in catalytic processes but also protect each other, resulting in more efficient removal of ROS, protection of cells against injury, and maintenance of the normal metabolism of ROS. To imitate the synergism of SOD and GPx, a 65-mer peptide (65P), containing sequences that form the domains of the active center of SOD and the catalytic triad of GPx upon the incorporation of some metals, was designed on the basis of native enzyme structural models; 65P was expressed in the cysteine auxotrophic expression system to obtain Se-65P. Se-65P was converted into Se–CuZn-65P by incorporating Cu2+ and Zn2+. Se–CuZn-65P exhibited high SOD and GPx activities because it has a delicate dual-activity center. The synergism of the enzyme mimic was evaluated by using an in vitro model and a xanthine/xanthine oxidase/Fe2+-induced mitochondrial damage model system. We anticipate that the peptide enzyme mimic with synergism is promising for the treatment of human diseases and has potential applications in medicine as a potent antioxidant.