Catalytic properties of three catalases from Kohlrabi (Brassica oleracea gongylodes)

Abstract

Catalase (EC 1.11.1.6) was extracted from kohlrabi bulbs (Brassica oleracea gongylodes) with 0.05 M phosphate buffer, pH 7.0. On the basis of kinetic studies and activity stain for catalase, only three
isoenzymes of catalases were detected in kohlrabi bulbs extract with pH optima at 4.5, 6.5 and 10. Highest catalytic efficiency (Vmax/Km) value was found for isoenzyme active at pH 6.5. Isoenzyme with
pH optima at 4.5 was very sensitive to azide and more resistant to cyanide in comparison to other two isoenzymes active in kohlrabi bulbs extract. Substrate inhibition was found only for the isoenzyme active at pH 4.5. Heat inactivation studies showed a decrease in catalases activity at temperatures above 50, 60 and 70°C for isoenzymes active at pH 6.5, 10 and 4.5, respectively.