Synthesis of the conjugate of superoxide dismutase with the copolymer of divinyl ether and maleic anhydride retaining enzymatic activity

Superoxide dismutase (SOD) was covalently conjugated with the copolymer of divinyl ether and maleic anhydride (DIVEMA) with average molecular weight of 30000 and a narrow molecular weight distribution . To avoid the crosslinkage and the decrease in enzymatic activity, a pH-reversible amino group-protecting agent, 1, 1-dimethylmaleic anhydride (DMMAn), was applied in the synthesis. The amino groups of SOD were firstly protected by DMMAn; and then, after the remaining amino groups were reacted with the acid anhydride groups of DIVEMA, the protective agent was removed by lowering of the pH to 6.0. By use of this protective agent the crosslinked product could be minimized. The DIVEMA-SOD conjugate could be purified by preparative GPC. The resulting DI-VEMA-SOD conjugate, free from native SOD, retained almost the same enzymatic activity as that of native SOD as determined by the method of McCord.