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.