In this study, we aimed to address if enzymes self-assembled on the biological nanosphere matrix would have some nanoscale effects and then improve the catalytic ability and other characteristics especially for the resistance to adverse conditions. Initially, we evaluated two different forms of ferritins, DNA-binding protein from starved cells (Dps) and recombinant heavy chain of human ferritin (rHF), fused with methyl parathion hydrolase (MPH) to be self-assembled as the dodecamer and 24-mer enzyme nanoparticles (enzyme-NPs), Dps-MPH and MPH-rHF. Both self-assembled enzyme-NPs showed superior catalytic activity and kcat drastically increased, but MPH-rHF showed better performance than Dps-MPH. Next, Escherichia coli alkaline phosphatase (EAP) and the canonical mutant EAP(D101S) were chosen to confirm if rHF-based self-assembly generally improves the catalysis of enzymes with the different catalytic abilities. Additionally, restoration of the enzyme native forms on the rHF shell by increasing the flexibility of the polylinker between the catalytic units and the nanoscaffold further improved the catalytic activities of enzyme-NPs. Some of the nanoparticles exhibited better residual activities under extreme conditions. Conclusively, the enzyme-NPs based on rHF self-assembly provided an effective strategy for enzyme engineering.
Keywords: catalytic activity; enzyme nanoparticle; nanocarrier; recombinant heavy chain of human ferritin; self-assembly.