PURIFICATION AND PROPERTIES OF A CATALASE FROM POTATO-TUBERS (SOLANUM-TUBEROSUM)

Catalase from potato tubers (Solanum tuberosum) has been purified to homogeneity. The purified enzyme had a low specific activity (approx. 3000 units/mg of protein) and a marked tendency to form aggregates. Polyacrylamide gel electrophoresis in the presence of SDS revealed a single 56 kDa peptide. The apparent molecular weight of the native protein was estimated to 224 kDa. Some homology was found between the N-terminal sequences of potato, Ipomea batatas, and bovine liver catalases. The enzyme exhibited optical absorbance maxima at 280, 403, 500, 535, and 620 nm, and its epr spectrum was characteristic of a hemoprotein with high-spin ferric iron. The pseudo first order rate constant was invariant for H2O2 concentrations ranging from 8 to 30 mM, but decreased rapidly at higher concentrations. Cyanide and azide were inhibitors, and 2-mercaptoethanol was a much more efficient inhibitor than for other catalases. No NADPH could be detected in the potato catalase; this was the first search for this dinucleotide in a plant catalase and its absence in the potato enzyme could be tentatively related to its lower propensity to form the compound II state. © 1990.