صدیقه هاشم نیا

In this study the carboxylic groups of glutamic acid and aspartic acid residues of catalase were chemically modified using the treatment of the enzyme with 1-ethyl-3-(3'-dimethylamino) carbodiimide hydrochloride and neomycin. The effect of covalent attachment of neomycin on enzymatic activity, conformational and aggregation properties of catalase was investigated. The results demonstrate that the modification of catalase with different concentrations of neomycin shows two different types of behavior depend on the concentration range of neomycin. In the concentration range from 0.0 to 5.2 mM the neomycin-modified catalase compared to the native enzyme exhibits more ?-helix content, reduced surface hydrophobicity, little enhancement in catalase activity, and a better protection against thermal aggregation, whereas, at concentrations greater than 5.2 mM the modified enzyme exhibits a significant decrease in catalase activity, and an increase in random coil content which may result in disorder in the protein structure and increase in thermal aggregation.