Regulation of Catalytic Activity via the Biomolecular Interactions Based on Enzyme–Nanoparticle Conjugates
Protein surface recognition provides an appealing tool to regulate protein–protein interactions and enzymatic activities in the field of biological science. We are interested in using nanoparticle (NP) to bind enzyme surfaces through multivalent interactions and then engineer the protein properties. In this study, we have investigated the activity of the enzyme–NP conjugates and demonstrated that adsorbing enzyme onto NPs significantly increased its enzymatic activity. We ascribe this event of the enzymatic reactions by kinetic and thermodynamic studies, which provide a way of understanding and predicting the catalytic behaviors of the enzyme-functionalized NPs. In addition, NPs are excellent systems for modeling enzymes’ surfaces because they can be readily fabricated on size scales comparable with those of their biomolecular targets. Therefore, we were curious to study whether varying the dimensions of the NPs would affect their catalytic reactions. We have developed a series of kinetic experiments to systematically analyze the NP size–dependent enzymatic activities, and have developed a model to explain the phenomenon. Kinetic studies revealed that association of enzyme with NPs did not influence the turnover number, but smaller NPs did promote the catalytic efficiency of enzyme by increasing its kinetic affinity. A shielding model, based on diffusion–collision theory, explains the correlation between the size effects and the kinetic responses of the enzyme–NP conjugates. This size-effect model provides chemical and physical meaning, leading to the observed substrate specificities and catalytic constants. From the combined kinetic and theoretical investigation of enzyme bound to NPs, we found that these conjugates acted as a controllable and efficient factor for modulating the activity of the enzyme. In nature, controllable modulation of enzyme activity is a potent means of regulating several cellular processes (e.g., signal transduction, biosynthesis, metabolism). The modulation of biocatalytic behavior is an attractive feature for exploitation in the field of nanobiotechnology.
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