Purification and characterization of two forms of Cu/Zn-superoxide dismutase from bovine erythrocytes by preparative isoelectric focusing

Two forms of Cu/Zn-superoxide dismutase with isoelectric points (pI) 6.3 and 5.2 were isolated from bovine erythrocytes by preparative isoelectric focusing. Both forms show a relative molecular weight of 32 000 daltons corresponding to the value reported for the monomer molecule. From spectral analysis the maximum in the ultraviolet region of the spectrum (276 nm) is identical for both forms of superoxide dismutase whereas the maxima in the visible region are different (for the pI 5.2 form the maximum lies at 405 nm and for the pI 6.3 form at 695 nm). The different migration of the enzymatically active zones toward the anode during electrophoresis in alkaline media corresponds to their different isoelectric points.