Biocatalytic cascades operating on macromolecular scaffolds and in confined environments

Biocatalytic cascades guide complex, efficient and selective intracellular transformations. These unique features originate from the spatial organization of the biocatalysts in confined cellular environments that allow the directional channelling of reaction intermediates across the cells. Here we address efforts directed towards the development of synthetic cell analogues and supramolecular ensembles acting as nano/microenvironments for operating biocatalytic cascades. Multienzyme systems are integrated within metal–organic frameworks, polymersomes, lipid-stabilized microdroplets and hydrogel microparticles acting as cell-like containments. Also, multienzyme systems are spatially positioned on one-dimensional DNA wires, two-dimensional DNA strips or origami tiles, and three-dimensional DNA origami bundles or cages, and specific protein–protein interactions or peptide–protein complexes provide versatile scaffolds for engineering enzyme assemblies. Biocatalytic cascades operating on these scaffolds or in confined nano/microenvironments reveal substantially enhanced reaction yields compared with the analogous diffusional mixtures of the biocomponents. Mechanistic pathways accounting for the enhanced biocatalytic activities and future challenges in developing and applying biocatalytic cascades are presented. Spatial organization of biocatalytic cascades can improve their performance. In this Review Article, Itamar Willner and colleagues discuss technologies to artificially confine and localize enzyme cascades, the origin of observed rate enhancements and potential applications of such designed systems.