A novel 76-mer peptide mimic with the synergism of superoxide dismutase and glutathione peroxidase.

The balance of oxidation and reduction in the body requires the synergistic effect of various antioxidant enzymes. Therefore, the construction of enzyme mimics with multiple antioxidant activities is important and beneficial for further research on the synergistic effects of antioxidant enzymes and their mechanism of action. To explore the synergistic effect of superoxide dismutase (SOD) and glutathione peroxidase (GPx), a 76-mer selenium-containing peptide (Se-76P) mimic containing the active SOD and GPx centers was designed. Moreover, a cell-penetrating peptide was introduced into Se-76P by structure modeling, and then, Se-76P was expressed by a single-protein production combined with the cysteine auxotrophic double-expression system of Escherichia coli. The results suggest that Se-76P exhibits SOD and GPx activities, following the GPx activity of 109 U/mg protein and the SOD activity of 1218 U/mg protein. The labeled Se-76P with FITC fluorescence was verified to enter the L02 cells successfully; it improved the antioxidant activity in cells and promoted the consumption of glucose and synthesis of glycogen. The injection of Se-76P subcutaneously decreased the levels of blood glucose and malondialdehyde of lipid peroxidation produced in mice, indicating that Se-76P had antioxidative properties and a certain regulatory role of glucose metabolism. The data analysis provides further clarification that Se-76P can regulate insulin signal transduction to play an insulin-like role, which not only has a greater significance for further elucidating the catalytic mechanism of the enzyme and their synergistic effects on each other but also has enormous medicinal potential.