Zwitterionic polymer-mediated immobilization of organophosphorus hydrolase enhances hydrolysis of methyl parathion by substrate enrichment

Abstract

Organophosphorus pesticides (OPPs) degradation is highly demanded due to the toxic nature of the pesticides that have caused serious environmental concerns. Biocatalytic hydrolysis using organophosphorus hydrolase (OPH) is an important way to OPPs degradation, but the poor stability of OPH severely hindered its extensive applications in environmental bioremediation. It is well known that immobilization is an efficient way of enzyme stabilization, so this work has proposed to immobilize OPH onto mesoporous silica nanoparticles coated with a zwitterionic polymer containing short hydrophobic chains. It is found that the zwitterionic polymer coating significantly modified the microenvironment, leading to the stabilization of the immobilized enzyme while keeping its activity toward methyl parathion hydrolysis. More importantly, the coating resulted in the substrate enrichment onto the carrier (capacity, 49.7 mmol·g−1; dissociation constant, 11.7 μM), so the immobilized OPH presented a much lower Michaelis constant (0.09 mM) than its free counterpart (0.34 mM) as revealed by kinetic studies. Consequently, the catalytic efficiency (kcat/Km) of the immobilized OPH was 2.41 times higher than free OPH. Thus, this work demonstrated the promise of the zwitterionic polymer-mediated immobilization strategy for OPH in enhancing the enzyme performance for the hydrolysis of OPPs that are of low concentration in open environments.