Zhang, ZD; Zhang, YB; Wu, QH; Zhang, G; Wang, F
Objective: To investigate the pepsin digestion characteristics and stability of recombinant human manganese-superoxide dismutase (rhMn-SOD). Methods: The rhMn-SOD was treated with mock gastric juice (0.084 mol/L hydrochloric acid, 35 mmol/L sodium chloride, pH 2.0, 4 000 U pepsin) at 37°C for various minutes, analyzed for digestion effect by SDS-PAGE. The relative activities of rhMn-SOD after storage at various temperatures(25, 37, 45, 55, 67 and 75°C) for various minutes (10, 20, 30, 40, 50 and 60 min) and at various pH values (4.0-10.0), after treatment with various compounds (chloramines, glycerol, DMSO, 10% SDS, β-mercaptoethanol, phenol, 30% hydrogen peroxide) and after exposure to sunlight and ultraviolet irradiation were determined by total SOD determination kit. Results: The rhMn-SOD was completely digested after treatment with mock gastric juice for 2 min, which showed high thermostability at 25-55°C and low thermostability at 65-75°C. The rhMn-SOD showed high stability at pH 6.0-8.0, and was insensitive to glycerol and chloramines, of which the activity decreased remarkably after treatment with DMSO and SDS and disappeared basically after treatment with P-mercaptoethanol, phenol and 30% hydrogen peroxide. However, the activity of rhMn-SOD showed no significant change after exposure to sunlight or to ultraviolet irradiation for 3 h. Conclusion: The pepsin digestion characteristics, thermostability, stability to pH value, sensitivities to various compounds as well as photostability of rhMn-SOD were analyzed, which laid a foundation of its application in various fields such as cosmetics, drugs and food additives.