Engineering a thermostable iron superoxide dismutase based on manganese superoxide dismutase from Thermus thermophilus

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.

Thermoacidophilic Alicyclobacillus Superoxide Dismutase: Good Candidate as Additives in Food and Medicine

Thermoacidophilic Alicyclobacillus strains attract great interests as the resource of thermostable or acidic enzymes. In this study, a putative gene encoding superoxide dismutase (AaSOD) was identified in a thermoacidophilic Alicyclobacillus strain. With a 16-fold activity observed, the AaSOD activity expressing in the medium of manganese enrichment was much higher than that in the iron medium. In addition, the purified AaSOD can be reconstituted exclusively with either Fe²⁺ or Mn²⁺, with its Mn-bound protein showing 25-fold activity than that of Fe-bound form. The optimal temperature for AaSOD reaction was 35°C, and was highly stable at any certain temperature up to 80°C. Of particular interest, the enzyme is found to be very stable across a wide pH range spanning from 2.0 to 10.0, which confers its robust stability in the acidic stomach environment and implies striking potentials as food additive and for medical use.

Small design from big alignment: engineering proteins with multiple sequence alignment as the starting point

Multiple sequence alignment (MSA) is a fundamental way to gain information that cannot be obtained from the analysis of any individual sequence included in the alignment. It provides ways to investigate the relationship between sequence and function from a perspective of evolution. Thus, the MSA of proteins can be employed as a reference for protein engineering. In this paper, we reviewed the recent advances to highlight how protein engineering was benefited from the MSA of proteins. These methods include (1) engineering the thermostability or solubility of proteins by making it closer to the consensus sequence of the alignment through introducing site mutations; (2) structure-based engineering proteins with comparative modeling; (3) creating paleoenzymes featured with high thermostability and promiscuity by constructing the ancestral sequences derived from multiple sequence alignment; and (4) incorporating site-mutations targeting the evolutionarily coupled sites identified from multiple sequence alignment.

Characterization of the biosynthetic pathway of nucleotide sugar precursor UDP-glucose during sphingan WL gum production in Sphingomonas sp. WG

To elucidate the possible biosynthetic pathway of a precursor UDP-glucose of the sphingan WL gum produced by Sphingomonas sp. WG, two enzymes phosphoglucomutase (PGM) and UDP-glucose pyrophosphorylase (UGPase) were bioinformatically analysed, expressed in Escherichia coli BL21 (DE3) and characterized. PGM was in the phosphoglucomutase/phosphomannomutase subclass and UGPase was predicted to be a UDP-glucose pyrophosphatase in a tetrameric structure. Both enzymes were expressed in soluble form, purified to near homogeneity with high activity at 1159 and 796 U/mg, exhibited folding with reasonable secondary structures, and existed as monomer and tetramer, respectively. The optimal pH and temperature of PGM were 9.0 and 50 °C, respectively, and this protein was stable at pH 8.0 and at temperatures ranging from 40 to 50 °C. The optimal pH and temperature of UGPase were 9.0 and 45 °C, respectively, and the protein was stable at pH 8.0 and at temperatures ranging from 30 to 55 °C. A small-scale one-pot biosynthesis of UDP-glucose by combining PGM and UGPase using glucose-6-phosphate and UTP as substrates was also performed, and formation of UDP-glucose was observed by HPLC detection, which confirmed the biosynthetic pathway of UDP-glucose in vitro. PGM and UGPase will be ideal targets for the metabolic engineering to improve WL gum yields in industrial production.