Altered Properties of Serratia Superoxide Dismutase by Chemical Modification1

Abstract

Serratia Mn-superoxide dismutase (SOD) was modified with dextran (Dx) of M.W. 80K and polyethyleneglycol (PEG) of M.W. 5K. SOD was modified at 34% of its free amino groups by Dx. DX-SOD retained 67% of the enzymatic activity of native SOD and had cross-reacted less with anti-SOD in vitro but higher immunogenicity against SOD in vivo. SOD was modified at 24% of the free amino groups by PEG. PEG-SOD retained 52% of the enzymatic activity, had lower antigenicity and immunogenicity, and induced immuno-tolerance to SOD. The half-life of PEG-SOD in the rat blood circulation was about ten times as long as that of SOD. PEG-modification of SOD enhanced its pharmacological activities as an anti-inflammatory and radioprotective agent.