Enhancement in enzymatic activity after attachment to nanoparticle surfaces has been observed in numerous enzyme systems, although the underlying mechanism for these enhancements remains largely unknown. This work explores the utility of a model based on a reaction scheme that takes into account some of the many interactions between substrate, product, and nanoparticle that can occur. This model was utilized to make predictions about the type of behavior that should manifest itself with quantum dots peripherally displayed around beta-galactosidase (&beta-gal) and confirmed empirically. &beta-gal is a homotetrameric enzyme which at ~465 kDa is significantly larger than the 4.2 nm diameter green emitting quantum dots utilized to decorate its periphery. Because &beta-gal operates near the diffusion limit, this provides an opportunity to selectively investigate certain aspects of enzyme enhancement when attached to a nanoparticle with minimal perturbation to the native enzyme structure. Enzymatic assays were performed with both free enzyme and quantum dot-decorated enzymes in a side-by-side format where kinetic processes were challenged by increasing viscosity with glycerol and competitive inhibitors such as lactose. The results from this model suggest it is possible to achieve significant enhancements in a diffusion limited enzyme’s catalytic rate (< i>k< sub>cat< sub>< i>) after NP attachment without substantial changes to the enzyme’s structure or function. Because cell free synthetic biology is gaining importance, this approach will yield insights on how enzymes can be utilized ex vivo and how being attached to NP scaffolds yields kinetic enhancement, possibly through enhanced product dissociation.
Joyce C. Breger, Anthony P. Malanoski, Carl W. Brown, Jeffery R. Deschamps, Kimhiro Susumu, Eunkeu Oh, George P. Anderson, Scott A. Walper, and Igor L. Medintz, "Probing kinetic enhancement of β-galactosidase-nanoparticle complexes (Conference Presentation)," Proc. SPIE 10507, Colloidal Nanoparticles for Biomedical Applications XIII, 1050709 (Presented at SPIE BiOS: January 27, 2018; Published: 15 March 2018); https://doi.org/10.1117/12.2289988.5752194237001.
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