Identification and characterization of a super-stable Cu–Zn SOD from leaves of turmeric (Curcuma longa L.)

We report a novel super stable superoxide dismutase (SOD) extracted from the leaves of Curcuma longa L.—a post-harvest waste. The scavenging activity of this SOD remains intact both in crude and purified forms before and after heating at boiling temperatures (80–100°C) up to 20 min, autoclaving (6–20 bars up to 10 min) and microwaving (frequency of 2,450 megahertz (MHz) or million cycles per second for 1–3 min). This SOD has significant shelf life at room temperature (25–35°C) and is stable for at least 18 months at 4°C and with the retained activity of 82% at −10°C and 88% at −20°C without any infection or contamination. The heat stable enzyme is present both in cytoplasm and chloroplasts. The enzyme is also stable under wide range of pH, alcohol and SDS concentrations. The heat stability of this SOD protein is not due to any associated phenolic compound as no phenolic compound was bound to the novel thermo-stable SOD. The activity staining through native PAGE and purification of the enzyme protein have shown that this form of enzyme has a native molecular weight of 30.8 kDa and has two subunits of 15 kDa as shown by SDS PAGE. The characterized novel isoform is a Cu–Zn SOD as is indicated by its sensitivity to both H2O2 and KCN. Indian, US and PCT patents have been filed and products are being developed using this hyperthermophilic enzyme.