Jm. Palma et al., PURIFICATION AND PROPERTIES OF CYTOSOLIC COPPER, ZINC SUPEROXIDE-DISMUTASE FROM WATERMELON (CITRULLUS-VULGARIS SCHRAD) COTYLEDONS, Free radical research, 26(1), 1997, pp. 83-91
Cytosolic copperzinc-superoxide dismutase (CuZn- SOD I; EC 1.15.1.1) w
as purified to homogeneity from watermelon (Citrullus vulgaris Schrad.
) cotyledons. The stepwise purification procedure consisted of acetone
precipitation, batch anion-exchange chromatography, anion-exchange Fa
st Protein Liquid Chromatography, gel filtration column chromatography
, and affinity chromatography on concanavalin A-Sepharose. CuZn-SOD I
was purified 310-fold with a yield of 12.6 micrograms enzyme per gram
cotyledons, and had a specific activity of 3,540 units per milligram p
rotein. The relative molecular mass for cytosolic CuZn-SOD was 34000,
and it was composed by two equal subunits of 16.3 kDa. CuZn-SOD I did
not contain neutral carbohydrates in its molecule, and its ultraviolet
and visible absorption spectra showed two absorption maxima at 254 nm
and 580 nm. Metal analysis showed that the enzyme contained 1 gram-at
om Cu and 1 gram-atom Zn per mole dimer. Cytosolic CuZn-SOD was recogn
ized by the antibody against peroxisomal CuZn-SOD from watermelon coty
ledons, and its enzymatic activity was inhibited by this antibody. By
IEF (pH 4.2-4.9), using a new method for vertical slab gels set up in
our laboratory, purified cytosolic CuZn-SOD was resolved into two equa
l isoforms with isoelectric points of 4.63 and 4.66.