Search

The art of designing coupling systems to drive reactions for endergonic synthesis is a subject of great interest in the scientific community, but it still presents major challenges. The aim of this kinetic study was to run simulations in COPASI 4.39 to test the behavior of hypothetical models for a system that couples two independent reactions, one exergonic and the other endergonic. In our computational study, we unraveled the qualitative and quantitative conditions that allow and benefit coupling, considering all possible reaction pathways within the network. Optimal conditions were reached by assigning favorable directionalities and low activation energies to six reaction steps within a network that featured twenty reaction steps. Moreover, different models were designed and tested in order to investigate the availability of coupling with different reaction steps. [ABSTRACT FROM AUTHOR]

Laccases that oxidize low-density polyethylene (LDPE) represent a promising strategy for bioremediation purposes. To rationalize or optimize their PE-oxidative activity, two fundamental factors must be considered: the enzyme's redox potential and its binding affinity/mode towards LDPE. Indeed, a stable laccase-PE complex may facilitate a thermodynamically unfavorable electron transfer, even without redox mediators. In this study, we compared the redox potential and the LDPE-binding properties of three different PE-oxidizing laccases: a fungal high-redox potential laccase from Trametes versicolor, a bacterial low-redox potential laccase from Bacillus subtilis, and the recently characterized LMCO2 from Rhodococcus opacus R7. First we found that LMCO2 is a low-potential laccase (E°=413 mV), as reported in other bacterial variants. Using computational tools, we simulated the interactions of these laccases with a large LDPE model and highlighted the key role of hydrophobic residues surrounding the T1 site. Notably, a methionine-rich loop in LMCO2 appears to enhance the formation of a stable complex with LDPE, potentially facilitating electron transfer. This study underscores the necessity for comprehensive computational strategies to analyze enzyme-polymer interactions beyond simplistic models, uncovering critical binding determinants and informing future mutagenesis experiments, in order to enhance laccase performance and rationalize variations in enzymatic activity., (© 2025 Wiley-VCH GmbH.)