Purification and Properties of Manganese Superoxide Dismutase from Norway Spruce (Picea abies L. Karst)

Abstract

A manganese-containing superoxide dismutase (SOD; EC 1.15.1.1) was purified to electrophoretic homogeneity from seeds of Norway spruce (Picea abies L.). The apparent molecular mass of the purified enzyme was 86 kDa, as determined by gel filtration. The subunit molecular mass, estimated by SDS-polyacrylamide gel electrophoresis, was 22 kDa both in the presence and in the absence of 2-mercaptoethanol. Thus, the native enzyme is a homotetramer with subunits that were not linked by disulfide bonds. The isoelectric point of this Mn-SOD was 5.5. The specific activity 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 exhibited a high degree of sequence homology to those of Mn-SODs from other organisms. In Mn-deficient needles the activity of Mn-SOD was only half of that in non-deficient needles, whereas the activity of CuZn-SOD was doubled.