Caharacterization of catalase from two different cucurbita seeds (Cucurbita maxima and moschata) grown in Sakarya

.Catalase (Hydrojen Peroxide Oxidoreductase, E.C: 1.11.1.6), converts hydrogen peroxide to water and contains heme as prostethic groups. In addition, catalase exist, in vertebrates, in vertebrates animals, plants and microorganisms with a high turnover number (4x 107 s-1). Catalase is a major primary antioxidant defense component that primarily works to catalase the decomposition of Hydrogen Peroxide to water.In this study, catalase was purified from cucurbita seeds (Cucurbita maxima and Cucurbita moschata) and some kinetic properties were studied. The purification was performed at three steps: Preparation of homogenate , ammonium sulphate fractionation and after dialysis, the enzymes were applied to G-100 sephadex column chromatography system. SDS - PAGE electrophoresis was applied for the determination of the enzymes molecular weights. They were found in three bands from 60 to 8 kDa in the electrophoresis for both seeds. Optimum pH, optimum temperature of the enzymes were found to be 6,8 ? 7,0 and 25 °C. Km and Vmax values were calculated. Cucurbita maxima Km=17,68 mM Vmax=81,300 EÜ/mL ; Cucurbita moschata Km=20,029 mM, Vmax=58,139 EÜ/mL. In addition to that, Heme catalase inhibitors, such as azide and cyanide, inhibited the enzyme activity markedly and KI values were calculated. For Cucurbita maxima and moschata azide KI = 0,66 0,04 ; cyanide KI = 2,42 0,01.Key words: Cucurbita seeds, Cucurbita maxima, Cucurbita moscahata, antioxidant enzymes, Catalase,, antioxidant system, hydrogen peroxide