RECOMBINANT HUMAN EXTRACELLULAR-SUPEROXIDE DISMUTASE PRODUCED IN MILKOF TRANSGENIC RABBITS

Expression of human extracellular superoxide dismutase (EC-SOD), a gly cosylated, tetrameric metalloprotein, was targeted to the lactating ma mmary grand of transgenic rabbits. Efficient expression of the recombi nant whey acidic protein/ec-sod gene was achieved and up to 3 mg ml(-1 ) of the enzyme was secreted into the milk. Rabbit milk-produced recom binant EC-SOD was primarily found in the whey and purified by a two-st ep chromatographic method. To evaluate the rabbit milk-produced human EC-SOD, comparisons with native and Chinese hamster ovary cell (CHO)-p roduced EC-SOD were performed. All proteins were tetrameric and N-glyc osylated. The behaviour on SDS-PAGE and size-exclusion chromatography indicated that the masses, and thereby the extent of post-translationa l modification of the proteins was similar. The monosaccharide composi tion of both recombinant EC-SOD variants was analysed and indicated si milarities in the attached N-glycans on the two proteins. Furthermore, the peptide maps of the three EC-SOD variants revealed that all prote ins had similar polypeptide backbones.