Abstract
Biocatalytic transformations in living organisms, such as multi-enzyme catalytic cascades, proceed in different cellular membrane-compartmentalized organelles with high efficiency. Nevertheless, it remains challenging to mimicking biocatalytic cascade processes in natural systems. Herein, we demonstrate that multi-shelled metal-organic frameworks (MOFs) can be used as a hierarchical scaffold to spatially organize enzymes on nanoscale to enhance cascade catalytic efficiency. Encapsulating multi-enzymes with multi-shelled MOFs by epitaxial shell-by-shell overgrowth leads to 5.8~13.5-fold enhancements in catalytic efficiencies compared with free enzymes in solution. Importantly, multi-shelled MOFs can act as a multi-spatial-compartmental nanoreactor that allows physically compartmentalize multiple enzymes in a single MOF nanoparticle for operating incompatible tandem biocatalytic reaction in one pot. Additionally, we use nanoscale Fourier transform infrared (nano-FTIR) spectroscopy to resolve nanoscale heterogeneity of vibrational activity associated to enzymes encapsulated in multi-shelled MOFs. Furthermore, multi-shelled MOFs enable facile control of multi-enzyme positions according to specific tandem reaction routes, in which close positioning of enzyme-1-loaded and enzyme-2-loaded shells along the inner-to-outer shells could effectively facilitate mass transportation to promote efficient tandem biocatalytic reaction. This work is anticipated to shed new light on designing efficient multi-enzyme catalytic cascades to encourage applications in many chemical and pharmaceutical industrial processes.
Highlights
Biocatalytic transformations in living organisms, such as multi-enzyme catalytic cascades, proceed in different cellular membrane-compartmentalized organelles with high efficiency
TEM imaging showed that both Glucose oxidase (GOx)@zeolitic imidazolate framework-8 (ZIF-8) and GOx@ZIF-8@horseradish peroxidase (HRP)@ZIF-8 grew into cubic-shaped nanoparticles (Fig. 1b and Supplementary Fig. 2) and the average particle sizes were increased from ~80 ± 9 nm (ZIF-8), ~120 ± 15 nm (GOx@ZIF-8), to ~180 ± 20 nm (GOx@ZIF8@HRP@ZIF-8) with enzymes encapsulated into different ZIF-8 shells (the corresponding particle size distribution based on dynamic light scattering (DLS) characterization is displayed in Supplementary Fig. 3)
Compared with other strategies, using multi-shelled metal-organic frameworks (MOFs) for designing multi-enzyme catalytic cascades provides several remarkable features: (i) The porous MOF scaffold provides a designated diffusion path for mass transfer between spatially confined enzymes’ active sites, promoting efficient operation of tandem biocatalytic reaction. (ii) The incompatible enzymes can be loaded independently in distinct domains of multi-shelled MOFs during epitaxial shell-by-shell overgrowth, providing spatial segregation for multi-step tandem reaction to occur simultaneously within single MOF nanoparticles in one pot. (iii) Multienzymes can be spatially confined with varied inter-enzyme distances by adjusting epitaxial overgrowth cycles, and with varied enzyme positions by adjusting encapsulation sequences; the tandem biocatalytic efficiency can be facilely regulated
Summary
Biocatalytic transformations in living organisms, such as multi-enzyme catalytic cascades, proceed in different cellular membrane-compartmentalized organelles with high efficiency. Multi-shelled MOFs can act as a multispatial-compartmental nanoreactor that allows physically compartmentalize multiple enzymes in a single MOF nanoparticle for operating incompatible tandem biocatalytic reaction in one pot. MOF capsules assembled at Pickering emulsion[19,30,31,32,33,34,35,36] and MOF chains linked by complementary peptides[37], were manipulated to form distinguished spatial compartments to trigger multi-enzyme catalytic cascade These systems immobilized different enzymes separately in MOF capsules or particles; reached limitations in catalytic efficiency due to slow transportations of intermediate products between compartments[19,37,38]. Using nano-FTIR spectroscopy, we chemically mapped the spatial organization of multi-enzymes in single multi-spatial-compartmental MOF particles with nanoscale resolution. This work provides important insights into developing complex multi-spatial compartmental systems for multi-enzyme catalytic cascades that hold great promise in many industrial processes
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