Deciphering the alkaline stable mechanism of bacterial laccase from Bacillus pumilus by molecular dynamics simulation can improve the decolorization of textile dyes

• Published in: Journal of hazardous materials 2023-02, Vol.443, p.130370-130370, Article 130370
• Main Authors: Liu, Jiashu, Li, Bianxia, Li, Zhuang, Yang, Fan, Chen, Bixin, Chen, Jianhui, Li, Huanan, Jiang, Zhengbing
• Format: Article
• Language: English
• Subjects: Alkaline resistance; Bacterial laccase; Conformational change; Dye decolorization; Molecular dynamics simulation
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.130370

Laccases are considered promising tools for removing synthetic dyes from textile and tannery effluents. However, the alkaline pH in the effluents causes laccase instability, inactivation, and difficulty in its bioremediation. Based on a Bacillus pumilus ZB1 (BpLac) derived alkaline stable laccase, this study aimed to elucidate its alkaline stable mechanism at molecular level using molecular dynamics simulation. The effects of metal ions, organic solvents, and inhibitors on BpLac activity were assessed. BpLac formed more salt bridges and negatively charged surface in alkaline environment. Thereafter, pH-induced conformation changes were analyzed using GROMACS at pH 5.0 and 10.0. Among the identified residues with high fluctuation, the distance between Pro359 and Thr414 was stable at pH 10.0 but highly variable at pH 5.0. DSSP analysis suggested that BpLac formed more β-sheet and less coil at pH 10.0. Principal component analysis and free energy landscape indicated that irregular coils formed at pH 5.0 benefit for activity, while rigid α-helix and β-sheet structures formed at pH 10.0 contributed to alkaline stability. Breaking the α-helix near T1 copper center would not reduce alkaline stability but could improve dye decolorization by BpLac. Overall, these findings would advance the potential application of bacterial laccase in alkaline effluent treatment. [Display omitted] •pH-induced conformational change of bacterial laccase affects activity and stability.•Salt bridges and negatively charged surface contribute to alkaline stability.•In silico study identified high fluctuation residues between acidic and alkaline pH.•Bacterial laccase formed more α-helix and β-sheet but less coil at pH 10.0.•Substitution of Leu with Pro at position 495 improves textile dye decolorization.