The Activity and Structure of Superoxide Dismutase of Lycium in the Existence of Zn2+ with Spectroscopy

As an important natural antioxidant, superoxide dismutase has been widely applied in fields such as diseases treatment as well as food, cosmetics and agriculture industries. In view of the poor stability of extraction quantity of SOD, the extraction of superoxide disutase from Lycium (SOD-LY) was carried out by salting-out separation with different levels of ammonium sulphate and reprecipitation with acetone in sequence. Its type was determined with ultraviolet spectrometry. The influence of different types of zinc salts such as ZnSO4, ZnCl2, Zn(CH3COO)(2), Zn(NO3)(2) on activity of SOD-LY was investigated. The zinc salt enhancing its activity effectively was selected. The mode of interaction between the zinc salt selected and SOD-LY was studied with Fourier transform infrared spectroscopy, ultraviolet spectrum and fluorescence spectrometry. The analysis of results of ultraviolet spectrometry had shown that the SOD-LY extracted in the experiments consisted the type of Cu/zinc-SOD. The activity of SOD-LY can be influenced by different concentration of zinc salts such as zinc nitrate, zinc acetate, zinc chloride, sulfuric acid zinc and ethylene glycol. Among the investigated zinc salts, the activity of SOD-LY can be enhanced through using Zn (NO3)(2) greatly. The analysis of infrared spectroscopy demonstrated that beta-sheet layer, beta-corner and beta-antiparallel all decrease, however, alpha- helix and unordered curling increases for the secondary structure of SOD-LY in the presence of Zn(NO3)(2), This may be due to the presence of weakly interacting complex between them. Analysis of fluorescence spectrometry indicated that the fluorescence intensity of SOD-LY decreased due to the addition of Zn(NO3)(2) whose binding constant was 1. 666X10(3) L . mol(-1) while the binding site number was 1. 238 according to the double logarithmic regression curve analysis. The distance is 3. 62 nm by overlapping coverage area of the UV absorption spectra of SOD-LY and the fluorescence emission spectra of Zn(NO3)(2)-SODLY. The main action existed between Zn2+ and SOD-LY is electrostatic forces (Delta H<O, Delta S>0). The study has a great theoretical significance for increasing the activity and stability of SOD, including the extension of its application.