Characterization of recombinant human extracellular superoxide dismutase

Recombinant human extracellular superoxide dismutase produced in chinese hamster ovary cells has been characterized using several chromatographic methods. Peptide mapping confirmed the expected primary structure. The 15 amino acids at the N-terminal end were sequenced and were in accordance with expectations in all positions. The C-terminal amino acids have been confirmed both by amino acid composition studies of a peptide of 42 amino acids and by specific sequential cleavage of the last three C-terminal amino acids with carboxypeptidase A. Both methods demonstrated a full length C-terminus. At physiological ionic strength, the dismutase exists for ca. 25% as octamers or larger polymers, and the amount of polymers increases at lower ionic strength.