PURIFICATION AND PROPERTIES OF MANGANESE SUPEROXIDE-DISMUTASE FROM NORWAY SPRUCE (PICEA-ABIES L KARST)

A manganese-containing superoxide dismutase (SOD; EC 1.15.1.1) was pur ified to electrophoretic homogeneity from seeds of Norway spruce (Pice a abies L.). The apparent molecular mass of the purified enzyme was 86 kDa, as determined by gel filtration. The subunit molecular mass, est imated by SDS-polyacrylamide gel electrophoresis, was 22 kDa both in t he presence and in the absence of 2-mercaptoethanol. Thus, the native enzyme is a homotetramer with subunits that were not linked by disulfi de bonds. The isoelectric point of this Mn-SOD was 5.5. The specific a ctivity of the Mn-SOD was strongly pH-dependent and was 400 units per nmol SOD at pH 7.8 and 30 units per nmol SOD at pH 10.4. The first 25 amino acid residues in the amino terminal region of spruce Mn-SOD exhi bited a high degree of sequence homology to those of Mn-SODs from othe r organisms. In Mn-deficient needles the activity of Mn-SOD was only h alf of that in non-deficient needles, whereas the activity of CuZn-SOD was doubled.