Engineering of supramolecular nanoreactors by assembly of multiple enzymes for ATP regeneration in vitro

Construction of Bi-Enzyme Self-Assembly Clusters Based on SpyCatcher/SpyTag for the Efficient Biosynthesis of (R)-Ethyl 2-hydroxy-4-phenylbutyrate

Cascade reactions catalyzed by multi-enzyme systems are important in science and industry and can be used to synthesize drugs and nutrients. In this study, two types of macromolecules of bi-enzyme self-assembly clusters (BESCs) consisting of carbonyl reductase (CpCR) and glucose dehydrogenase (GDH) were examined. Stereoselective CpCR and GDH were successfully fused with SpyCatcher and SpyTag, respectively, to obtain four enzyme modules, namely: SpyCatcher-CpCR, SpyCatcher-GDH, SpyTag-CpCR, and SpyTag-GDH, which were covalently coupled in vitro to form two types of hydrogel-like BESCs: CpCR-SpyCatcher-SpyTag-GDH and GDH-SpyCatcher-SpyTag-CpCR. CpCR-SpyCatcher-SpyTag-GDH showed a better activity and efficiently converted ethyl 2-oxo-4-phenylbutyrate (OPBE) to ethyl(R)2-hydroxy-4-phenylbutanoate ((R)-HPBE), while regenerating NADPH. At 30 °C and pH 7, the conversion rate of OPBE with CpCR-SpyCatcher-SpyTag-GDH as a catalyst reached 99.9%, with the ee% of (R)-HPBE reaching above 99.9%. This conversion rate was 2.4 times higher than that obtained with the free bi-enzyme. The pH tolerance and temperature stability of the BESCs were also improved compared with those of the free enzymes. In conclusion, bi-enzyme assemblies were docked using SpyCatcher/SpyTag to produce BESCs with a special structure and excellent catalytic activity, improving the catalytic efficiency of the enzyme.

Programming Integrative Multienzyme Systems and Ionic Strength For Recyclable Synthesis of Glutathione

In the enzymatic cascade catalysis, it is a big challenge to construct a stable and reusable catalyst with targeted enzymes. The artificial multienzyme reactor has attracted great attention due to its potential for facilitating the performance of enzyme catalysis. In this study, we set up a reliable system that could assemble polyphosphate kinase (PPK) with bifunctional glutathione synthetase (GshF) via SpyCatcher/SpyTag to form multienzyme systems (MESs). Furthermore, MESs could assemble into nanoaggregates by altering the ionic strength, and the larger nanoaggregates could be applied in robust and reusable synthesis of glutathione (GSH). To enhance MES levels in vivo, gene duplication and different coexpression modes were performed. Finally, the optimized production of GSH and oxidized glutathione (GSSG) reached 102.6 and 6.7 mM within 2 h. Compared with the first round, the total yield only decreased by 9.4% after five continuous rounds of biocatalysis.

Enzymatic regeneration and conservation of ATP: challenges and opportunities

Adenosine triphosphate (ATP), the universal energy currency of life, has a central role in numerous biochemical reactions with potential for the synthesis of numerous high-value products. ATP can be regenerated by three types of mechanisms: substrate level phosphorylation, oxidative phosphorylation, and photophosphorylation. Current ATP regeneration methods are mainly based on substrate level phosphorylation catalyzed by one enzyme, several cascade enzymes, or in vitro synthetic enzymatic pathways. Among them, polyphosphate kinases and acetate kinase, along with their respective phosphate donors, are the most popular approaches for in vitro ATP regeneration. For in vitro artificial pathways, either ATP-free or ATP-balancing strategies can be implemented via smart pathway design by choosing ATP-independent enzymes. Also, we discuss some remaining challenges and suggest perspectives, especially for industrial biomanufacturing. Development of ATP regeneration systems featuring low cost, high volumetric productivity, long lifetime, flexible compatibility, and great robustness could be one of the bottom-up strategies for cascade biocatalysis and in vitro synthetic biology.