Zhenkun Lu’s research while affiliated with Shandong Normal University and other places

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Publications (1)

Comparison of amino acid sequences of StKatG homologs. (A) Sequence alignment of StKatG1 and StKatG2. The sequences were aligned using the Clustal Omega and treated with ESPript 3 (https://espript.ibcp.fr/). The secondary structure elements presented on top were obtained from the predicted StKatG2 structure using Alphafold3 (α, α-helices; η, 3 10 helices; β, β-strands. TT, turns). Identical and similar residues are displayed in red and blue boxes, respectively. (B) Phylogenetic tree of KatG proteins from Salinicola tamaricis and other species. StKatG1 and StKatG2, Salinicola tamaricis KatGs; DkKatG, Drosophila kikkawai KatG; BpKatG, Burkholderia pseudomallei KatG; SeKatG, Salmonella enterica KatG; EcKatG, Escherichia coli KatG; SdKatG, Shigella dysenteriae KatG; RpKatG, Ralstonia pickettii KatG; BtKatG, Burkholderia thailandensis KatG; MpKatG, Methylibium petroleiphilum KatG; AvCP01, Azotobacter vinelandii KatG. The evolutionary analyses were conducted based on amino acid homology using the MEGA7. Bootstrap values are shown at branch points. (C) Predicted structures of StKatG1 and StKatG2 using AlphaFold3, with the manganese binding site in StKatG2 represented as a purple sphere.
Characterization of StKatG2. (A) The LBB assay for the formation of Mn oxides by incubating purified recombinant StKatG2 (0.3 mg protein/mL) with MnCl2 (50 mmol/L). Tube 1–3: sample after 24 h of incubation in the presence of StKatG2; tube 4: Negative control after 24 h in the absence of StKatG2. (B) The reaction kinetics of StKatG2 (0.3 mg protein/mL) were analyzed using various concentrations of MnCl2. The data presented are the averages of three independent experiments, accompanied by standard error bars. The curve was fitted using the Michaelis–Menten equation.
Morphology and composition of BioMnOx catalyzed by StKatG2. The BioMnOx were obtained through incubation of MnCl2 (50 mmol/L) and StKatG2 (0.5 mg/mL) at 50°C for 10 h. (A) The SEM photograph of the Mn oxide aggregates produced by StKatG2. Scale bar, 10 μm. (B) The SEM photograph of the Mn oxide aggregates at a different magnification with (A). Scale bar, 1 μm. (C) The EDS spectrum showing the Mn composition of the aggregates. The rectangle shown in figure A indicates the selected position of the aggregates. The unlabeled peaks are Au formed by the spray gold treatment. (D) The XRD pattern of the BioMnOx produced by StKatG2. (E) XPS wide scan patterns. (F) The deconvoluted profile of the specific Mn 2p1/2 and Mn 2p2/3 spectrum for the BioMnOx.
Effects of temperature and pH on Mn(II)-oxidizing activities of StKatG2. (A) Mn(II)-oxidizing activities of StKatG2 at different pH values. (B) Mn(II)-oxidizing activities of StKatG2 at different temperatures. (C) Thermostability of StKatG2 at various temperatures. StKatG2 was incubated at 50°C (red circles), 60°C (green circles), 70°C (orange triangles), and 80°C (blue triangles) for different time intervals, with residual activities measured at 50°C. The error bars indicate standard deviation.
Effects of different metal ions and EDTA on the Mn(II)-oxidizing activity of StKatG2. Effects of different concentrations of metal ions and EDTA at 0.1 mM (A), 1 mM (B), and 10 mM (C) on enzymatic activity the Mn(II)-the oxidizing activity of StKatG2. **, ***, and **** represent significant differences from the control group (**p < 0.01, ***p < 0.001, ****p < 0.0001).

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Catalase-peroxidase StKatG2 from Salinicola tamaricis: a versatile Mn(II) oxidase that decolorizes malachite green
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November 2024

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12 Reads

Mengyao Ding

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Wenjing Wang

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Zhenkun Lu

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Manganese (Mn) oxidation processes have garnered significant attention recently due to their potential for degrading organic pollutants. These processes are primarily catalyzed by Mn(II) oxidases. Salinicola tamaricis F01, an endophytic bacterium derived from wetland plants, has demonstrated Mn(II)-oxidizing capacity. In this study, a catalase-peroxidase, StKatG2, was cloned and overexpressed in Escherichia coli from the strain F01. The purified recombinant StKatG2 exhibited Mn(II)-oxidizing activity with Km and Kcat values of 2.529 mmol/L and 2.82 min⁻¹, respectively. Optimal catalytic conditions for StKatG2 were observed at pH 7.5 and 55°C, with 45.1% activity retention after an 8-h exposure to 80°C. The biogenic manganese oxides produced by StKatG2 exhibited mixed-valence states with Mn(II), including Mn(III), Mn(IV), and Mn(VII). Furthermore, StKatG2 demonstrated superior decolorization efficiency for malachite green (MG), achieving decolorization rates of 73.38% for 20 mg/L MG and 60.08% for 50 mg/L MG, while degrading MG into 4-(dimethylamino)benzophenone. Therefore, the catalase-peroxidase StKatG2 exhibits multifunctionality in Mn(II)-oxidizing activity and has the potential to serve as an environmentally friendly enzyme for MG removal.

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