Novel Thermostable Manganese Superoxide Dismutase from Alicyclobacillus sp. with High Specific Activity and Antioxidant Properties

Superoxide dismutase (SOD) is a vital antioxidant enzyme that exerts antioxidative and anti-inflammatory effects on the host. In this study, a novel thermostable SOD of Alicyclobacillus sp. (AliSOD) from a hot spring was overexpressed in Escherichia coli, and enzymatic properties were identified. Mn²⁺ plays a decisive role in enzyme activity, indicating that AliSOD is MnSOD. Specifically, AliSOD was determined to be dimeric with a subunit molecular mass of 23.0 kDa, and the specific activity was confirmed to be as high as 24990.8 U·mg^-1. AliSOD demonstrated exceptional thermal stability, broad pH stability, and resistance to urea, exhibiting minimal loss of activity at 70 °C and remarkable tolerance in an alkaline environment. Moreover, AliSOD significantly alleviated oxidative stress in diquat-injured cells (P < 0.01). It also increased intracellular SOD expression and activated the Nrf2 protein downstream of the Keap1-Nrf2 signaling pathway (P < 0.05). Overall, AliSOD exhibits excellent thermostability and specific activity, indicating potential applications in the pharmaceutical, food, and animal feed industries.