Fan_2025_J.Hazard.Mater_499_140315

Carboxylesterase (CarE) functions as an enzymatic detoxifier, helping mitigate ester-based pollutants in soil. Understanding CarE activity in soil environments is crucial for effective pollutant degradation and ecosystem health. However, the mechanistic interactions between CarE's functionality and soil components remain elusive. This study investigates the role of humic substances, key components of soil organic matter (SOM), in regulating CarE activity and pollutant degradation using enzyme incubation assays and molecular simulations. Fulvic acid (FA) modulates CarE activity, with effects depending on its concentration and soil conditions. FA enhances CarE activity and the degradation efficiency of ester-based compounds in neutral to alkaline environments, but inhibits the enzyme's function in acidic conditions. In contrast, humic acid (HA) activates CarE in a lesser extent. This activation is driven by CarE-SOM aggregation, where molecular interactions like electrostatic forces and van der Waals forces strengthen the aggregation. Spectroscopic analyses revealed that SOM binding expands CarE's structure in polar environments. Moreover, molecular simulations showed that SOM stabilizes the enzyme's catalytic region, enhancing substrate access by inducing movement in CarE's flexible loop regions. This research improves our understanding of pollutant degradation in soils, offering insights into bioremediation and soil management.