Mechanisms in structure-activity remodeling of extracellular enzymes at water-mineral interfaces

Extracellular enzymes from plants and microorganisms drive soil nutrient recycling, yet how mineral interfaces regulate enzyme activity remain unclear. Here, we investigated two extracellular phosphatases, from plant Ipomoea batatas and fungus Aspergillus niger , interacting with quartz, goethite, and illite. Enzyme kinetics, molecular modeling, and infrared spectroscopy were combined to resolve interfacial mechanisms controlling catalysis. For plant phosphatase, despite comparable adsorbed fractions, activity loss was 17% greater on illite than on goethite or quartz. Stronger inhibition by illite was consistent with direct surface interactions that suppressed enzyme flexibility, whereas water-mediated interactions on goethite and quartz caused minor perturbations of catalytic core. For fungal phosphatase, adsorption was up to 3-fold higher on illite than on goethite or quartz, but activity loss differed by only about 10%. Illite promoted rigid β-sheet–rich conformation with reduced α-helix and random-coil content, while weaker binding on goethite and quartz produced transient structural perturbations that caused activity loss.