Enzymatic reactions in confined environments

Abstract

Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems.

Biomimicry Promotes the Efficiency of a 10‐Step Sequential Enzymatic Reaction on Nanoparticles, Converting Glucose to Lactate

“…However, this chemistry is not site-specific and does not inherently impart proper molecular orientation—two factors that can lead to significant reduction in function of the tethered enzyme [2] . Use of self-assembly templates can immobilize and orient enzymes; for instance sequential reactions of glucose oxidase and horseradish peroxidase have been demonstrated using a DNA scaffold to control enzyme spacing [3] . Recently, the sequential reaction of three enzymes conjugated to quantum dots was demonstrated [4] .…”

“…This demonstrates that flux through the entire system was more efficient for the tethered enzymes. In biological systems, several mechanis ms of substrate channeling have been described [10] , with demonstrations that intermediates can move within the hydration shells around adjacent proteins, and that other intervening proteins can provide a hydration bridge [3a-c, 11] . Such models are highly compatible with our data, in which multiple enzymes were tethered to single NPs.…”

“…Our new findings create a foundation demonstrating that complex biological systems can be integrated into hybrid organic-inorganic devices, enabling other advantages of tethering such as spatiotemporal control of the reactions, and improved stability [3b, 3c] . Future applications for tethered enzymes range from in vivo (e.g.…”

Self-assembling all-enzyme hydrogels for biocatalytic flow processes

“…It is evident from natural examples that compartmentalized reaction systems offer advantages when intermediate species are prone to escape into competing reaction channels [3][4][5][6][7][8] . The GDH-ST/SC-LbADH hydrogels can be used to investigate this phenomenon because the NADPH consuming LbADH reduction is spatially and kinetically coupled to the NADPH regeneration by GDH.…”

“…Towards the goal of the efficient use of renewable biomass as an alternative to petrochemical synthesis for sustainable production processes and energy supply in the future, multistep enzymatic cascade reactions are currently attracting much attention [3][4][5][6][7][8] . Such cascades are abundant in living systems, for instance, to maintain the regulation of metabolic activity or signal transduction [9][10][11] .…”