Molecular Thermodynamic Origin of Substrate Promiscuity in the Enzyme Laccase: Toward a Broad-Spectrum Degrader of Dye Effluents

Industrial dye effluents have emerged as significant health hazard. Laccases found in white rot fungi can degrade an assortment of dyes. Here, we explore the molecular thermodynamic origin of the substrate promiscuity in laccases using a combination of steady-state UV-visible absorption spectroscopy, molecular docking, and molecular dynamics (MD) simulation studies on the interaction of laccase with five dye molecules with varying charge, size, and shape. The spectroscopic studies confirm that all of these dyes can be degraded by laccase. Using MD simulations, we have demonstrated the presence of various distinct conformations of a loop in the protein active site that can accommodate the wide range of dye molecules. We have also shown that the diverse selection of dye molecules may exhibit surprisingly similar binding affinity due to cancellation of different thermodynamic factors. Our results highlight the potential of laccase as a multipurpose degrader for industrial dye effluents.

Automated summary

Industrial dye effluents are a significant health hazard, but laccases in white rot fungi can degrade a variety of dyes. In this study, a combination of spectroscopy, molecular docking, and MD simulation was used to investigate the thermodynamic origin of substrate promiscuity in laccases. The results showed that laccase could degrade different dyes and accommodate their diverse structures through conformational changes. Additionally, the study revealed that despite diverse selection, the binding affinity of dye molecules was surprisingly similar due to cancellation of different thermodynamic factors. These findings highlight the potential of laccase as a versatile degrader for industrial dye effluents.