Copper, zinc superoxide dismutase from Caragana jubata: A thermostable enzyme that functions under a broad pH and temperature window

•A highly thermostable Cu, Zn superoxide dismutase (SOD) was cloned and characterized from Caragana jubata.•This enzyme tolerated autoclaving and operated under a broad window of temperature and pH.•The half-time of thermal inactivation for Cj-Cu, Zn SOD was 95 ± 21min.•Resistance to sodium dodecyl sulfate (SDS) binding, urea, and heat denaturation suggested its kinetic stability.•Further analysis of 94 phylogenetically diverse plants revealed the presence of autoclavable SOD in 15 species.

This study reports a thermostable Cu, Zn superoxide dismutase (SOD) obtained from a high-altitude plant Caragana jubata (Cj-Cu, Zn SOD). The expression of Cj-Cu, Zn SOD in Escherichia coli followed by purification yielded a 17.5 kDa protein with a specific activity of 1547 ± 39 units/mg of protein at 0 °C. The enzyme (i) functioned across a temperature range of −10 to +80 °C with optimum activity at 0-4 °C; (ii) performed well in a pH range of 6-9 with optimum activity at pH 7.5; (iii) was resistant to denaturation by sodium dodecyl sulfate (SDS) and urea; and (iv) existed in both monomeric and dimeric forms, the latter being more active. The enzyme exhibited activity upto 80 °C (kd = 8.00 ± 0.17 × 10−3 min−1, t1/2 = 95 ± 21 min), and tolerated autoclaving (heating at 121 °C at a pressure of 1.1 kg/cm2 for 20 min). Circular dichroic spectroscopy analysis confirmed the thermostable nature of Cj-Cu, Zn SOD. Analysis in 94 phylogenetically diverse plant species across varied habitat preferences revealed the presence of autoclavable SOD in 15 species. SODs with unique properties of thermo/kinetic stability can be exploited for various applications in cosmetic, food, and pharmaceutical industries.

Graphical abstractDownload high-res image (145KB)Download full-size image