Stimulus-Responsive Regulation of Enzyme Activity for One-Step and Multi-Step Syntheses

sp2-Iminosugar azobenzene O-glycosides: Light-sensitive glycosidase inhibitors with unprecedented tunability and switching factors

The conventional approach to developing light-sensitive glycosidase activity regulators, involving the combination of a glycomimetic moiety and a photoactive azobenzene module, results in conjugates with differences in glycosidase inhibitory activity between the interchangeable E and Z-isomers at the azo group that are generally below one-order of magnitude. In this study, we have exploited the chemical mimic character of sp2-iminosugars to access photoswitchable p- and o-azobenzene α-O-glycosides based on the gluco-configured representative ONJ. Notably, we achieved remarkably high switching factors for glycosidase inhibition, favoring either the E- or Z-isomer depending on the aglycone structure. Our data also indicate a correlation between the isomeric state of the azobenzene module and the selectivity towards α- and β-glucosidase isoenzymes. The most effective derivative reached over a 103-fold higher inhibitory potency towards human β-glucocerebrosidase in the Z as compared with the E isomeric form. This sharp contrast is compatible with ex-vivo activation and programmed self-deactivation at physiological temperatures, positioning it as a prime candidate for pharmacological chaperone therapy in Gaucher disease. Additionally, our results illustrate that chemical tailoring enables the engineering of photocommutators with the ability to toggle inhibition between α- and β-glucosidase enzymes in a reversible manner, thus expanding the versatility and potential therapeutic applications of this approach.

Unnatural enzyme activation by a metal-responsive regulatory protein

As a result of calcium ion binding, the calcium-dependent regulatory protein calmodulin (CaM) undergoes a conformational change, enabling it to bind to and activate a variety of enzymes. However, the detoxification enzyme glutathione S-transferase (GST) is notably not among the enzymes activated by CaM. In this study, we demonstrate the feasibility of establishing, in vitro, an artificial regulatory link between CaM and GST using bifunctional chemical transducer (CT) molecules possessing binders for CaM and GST. We show that the CTs convert the constitutively active GST into a triggerable enzyme whose activity is unnaturally regulated by the CaM conformational state and consequently, by the level of calcium ions. The ability to reconfigure the regulatory function of CaM demonstrates a novel mode by which CTs could be employed to mediate artificial protein crosstalk, as well as a new means to achieve artificial control of enzyme activity by modulating the coordination of metal ions. Within this study, we also investigated the impact of covalent interaction between the CTs and the enzyme target. This investigation offers further insights into the mechanisms governing the function of CTs and the possibility of rendering them isoform specific.

Opportunities for nanomaterials in enzyme therapy

In recent years, enzyme therapy strategies have rapidly evolved to catalyze essential biochemical reactions with therapeutic potential. These approaches hold particular promise in addressing rare genetic disorders, cancer treatment, neurodegenerative conditions, wound healing, inflammation management, and infectious disease control, among others. There are several primary reasons for the utilization of enzymes as therapeutics: their substrate specificity, their biological compatibility, and their ability to generate a high number of product molecules per enzyme unit. These features have encouraged their application in enzyme replacement therapy where the enzyme serves as the therapeutic agent to rectify abnormal metabolic and physiological processes, enzyme prodrug therapy where the enzyme initiates a clinical effect by activating prodrugs, and enzyme dynamic or starving therapy where the enzyme acts upon host substrate molecules. Currently, there are >20 commercialized products based on therapeutic enzymes, but approval rates are considerably lower than other biologicals. This has stimulated nanobiotechnology in the last years to develop nanoparticle-based solutions that integrate therapeutic enzymes. This approach aims to enhance stability, prevent rapid clearance, reduce immunogenicity, and even enable spatio-temporal activation of the therapeutic catalyst. This comprehensive review delves into emerging trends in the application of therapeutic enzymes, with a particular emphasis on the synergistic opportunities presented by incorporating enzymes into nanomaterials. Such integration holds the promise of enhancing existing therapies or even paving the way for innovative nanotherapeutic approaches.

Limits of Non-invasive Enzymatic Activation by Local Temperature Control

Enzymatic activity depends on and can therefore be regulated by temperature. Selective modulation of the activity of different enzymes in one reaction pot would require temperature control local to each type of enzyme. It has been suggested previously that immobilization of enzyme on magnetic nanoparticles and exposing them to alternating magnetic field can enhance the reaction rate. This enhancement has been explained as being mediated by temperature increase caused by dissipation of the absorbed field energy in the form of heat. However, the possibility of spatially limiting this temperature increase on the microscale has been questioned. Here, it is investigated whether an activity enhancement of the enzyme sucrose phosphorylase immobilized on magnetic beads can be achieved, how this effect is related to the increase in temperature, and whether temperature differences within one reaction pot could be generated in this way. It is found that alternating magnetic field stimulation leads to increased enzymatic activity fully attributable to the increase of bulk temperature. Both theoretical analysis and experimental data indicate that no local heating near the particle surface takes place. It is further concluded that relevant increase of surface temperature can be obtained only with macroscopic, millimeter-sized, magnetic particles.

Plasmonic-Driven Regulation of Biomolecular Activity In Situ

Selective and remote manipulation of activity for biomolecules, including protein, DNA, and lipids, is crucial to elucidate their molecular function and to develop biomedical applications. While advances in tool development, such as optogenetics, have significantly impacted these directions, the requirement for genetic modification significantly limits their therapeutic applications. Plasmonic nanoparticle heating has brought new opportunities to the field, as hot nanoparticles are unique point heat sources at the nanoscale. In this review, we summarize fundamental engineering problems such as plasmonic heating and the resulting biomolecular responses. We highlight the biological responses and applications of manipulating biomolecules and provide perspectives for future directions in the field.

Synthesis of Chiral Sulfoxides by A Cyclic Oxidation-Reduction Multi-Enzymatic Cascade Biocatalysis

Optically pure sulfoxides are valuable organosulfur compounds extensively employed in medicinal and organic synthesis. In this study, we present a biocatalytic oxidation-reduction cascade system designed for the preparation of enantiopure sulfoxides. The system involves the cooperation of a low-enantioselective chimeric oxidase SMO (styrene monooxygenase) with a high-enantioselective reductase MsrA (methionine sulfoxide reductase A), facilitating "non-selective oxidation and selective reduction" cycles for prochiral sulfide oxidation. The regeneration of requisite cofactors for MsrA and SMO was achieved via a cascade catalysis process involving three auxiliary enzymes, sustained by cost-effective D-glucose. Under the optimal reaction conditions, a series of heteroaryl alkyl, aryl alkyl and dialkyl sulfoxides in R configuration were synthesized through this "one-pot, one step" cascade reaction. The obtained compounds exhibited high yields of >90 % and demonstrated enantiomeric excess (ee) values exceeding 90 %. This study represents an unconventional and efficient biocatalytic way in utilizing the low-enantioselective oxidase for the synthesis of enantiopure sulfoxides.

Exploring Emergent Properties in Enzymatic Reaction Networks: Design and Control of Dynamic Functional Systems

The intricate and complex features of enzymatic reaction networks (ERNs) play a key role in the emergence and sustenance of life. Constructing such networks in vitro enables stepwise build up in complexity and introduces the opportunity to control enzymatic activity using physicochemical stimuli. Rational design and modulation of network motifs enable the engineering of artificial systems with emergent functionalities. Such functional systems are useful for a variety of reasons such as creating new-to-nature dynamic materials, producing value-added chemicals, constructing metabolic modules for synthetic cells, and even enabling molecular computation. In this review, we offer insights into the chemical characteristics of ERNs while also delving into their potential applications and associated challenges.

Up- and Down-Regulation of Enzyme Activity in Aggregates with Gold-Covered Magnetic Nanoparticles Triggered by Low-Frequency Magnetic Field

The modern global trend toward sustainable processes that meet the requirements of "green chemistry" provides new opportunities for the broad application of highly active, selective, and specific enzymatic reactions. However, the effective application of enzymes in industrial processes requires the development of systems for the remote regulation of their activity triggered by external physical stimuli, one of which is a low-frequency magnetic field (LFMF). Magnetic nanoparticles (MNPs) transform the energy of an LFMF into mechanical forces and deformations applied to enzyme molecules on the surfaces of MNPs. Here, we demonstrate the up- and down-regulation of two biotechnologically important enzymes, yeast alcohol dehydrogenase (YADH) and soybean formate dehydrogenase (FDH), in aggregates with gold-covered magnetic nanoparticles (GCMNPs) triggered by an LFMF. Two types of aggregates, "dimeric" (with the enzyme attached to several GCMNPs simultaneously), with YADH or FDH, and "monomeric" (the enzyme attached to only one GCMNP), with FDH, were synthesized. Depending on the aggregate type ("dimeric" or "monomeric"), LFMF treatment led to a decrease (down-regulation) or an increase (up-regulation) in enzyme activity. For "dimeric" aggregates, we observed 67 ± 9% and 47 ± 7% decreases in enzyme activity under LFMF exposure for YADH and FDH, respectively. Moreover, in the case of YADH, varying the enzyme or the cross-linking agent concentration led to different magnitudes of the LFMF effect, which was more significant at lower enzyme and higher cross-linking agent concentrations. Different responses to LFMF exposure depending on cofactor presence were also demonstrated. This effect might result from a varying cofactor binding efficiency to enzymes. For the "monomeric" aggregates with FDH, the LFMF treatment caused a significant increase in enzyme activity; the magnitude of this effect depended on the cofactor type: we observed up to 40% enzyme up-regulation in the case of NADP+, while almost no effect was observed in the case of NAD+.

Enzymatic Oxy- and Amino-Functionalization in Biocatalytic Cascade Synthesis: Recent Advances and Future Perspectives

Biocatalytic cascades are a powerful tool for building complex molecules containing oxygen and nitrogen functionalities. Moreover, the combination of multiple enzymes in one pot offers the possibility to minimize downstream processing and waste production. In this review, we illustrate various recent efforts in the development of multi-step syntheses involving C-O and C-N bond-forming enzymes to produce high value-added compounds, such as pharmaceuticals and polymer precursors. Both in vitro and in vivo examples are discussed, revealing the respective advantages and drawbacks. The use of engineered enzymes to boost the cascades outcome is also addressed and current co-substrate and cofactor recycling strategies are presented, highlighting the importance of atom economy. Finally, tools to overcome current challenges for multi-enzymatic oxy- and amino-functionalization reactions are discussed, including flow systems with immobilized biocatalysts and cascades in confined nanomaterials.

Neuritin affects the activity of neuralized-like 1 by promoting degradation and weakening its affinity for substrate

Neuritin plays a key role in neural development and regeneration by promoting neurite outgrowth and synapse maturation. Our previous research revealed the mechanism by which neuritin inhibits Notch signaling through interaction with neuralized-like 1 (Neurl1) to promote neurite growth. However, how neuritin regulates Notch signaling through Neurl1 has not been elucidated. Here, we first confirm that neuritin is an upstream regulator of Neurl1 and inhibits Notch signaling through Neurl1. Neurl1 is an E3 ubiquitin ligase that can promote ubiquitination and endocytosis of the Notch1 ligand Jagged1. Therefore, we observe the effect of neuritin on the ligase activity of Neurl1. The results indicate that neuritin inhibits Neurl1 activity by reducing the ubiquitination level and endocytosis of the target protein Jagged1. Moreover, we find that decreased activity of Neurl1 results in reduced expression of Notch receptor Notch intracellular domain (NICD) and downstream target gene hairy and enhancer of split-1 ( HES1). Furthermore, we investigate how neuritin affects Neurl1 enzyme activity. The results show that neuritin not only weakens the affinity between Neurl1 and Jagged1 but also promotes the degradation of Neurl1 by the 26S proteasome pathway. Taken together, our results suggest that neuritin negatively regulates Notch signaling by inhibiting the activity of Neurl1, promoting the degradation of Neurl1 and weakening the affinity of Neurl1 for Jagged1. Our study clarifies the molecular mechanisms of neuritin in regulating the Notch signaling pathway and provides new clues about how neuritin mediates neural regeneration and plasticity.

Energy Transfer from Magnetic Iron Oxide Nanoparticles: Implications for Magnetic Hyperthermia

Magnetic iron oxide nanoparticles (IONPs) have gained momentum in the field of biomedical applications. They can be remotely heated via alternating magnetic fields, and such heat can be transferred from the IONPs to the local environment. However, the microscopic mechanism of heat transfer is still debated. By X-ray total scattering experiments and first-principles simulations, we show how such heat transfer can occur. After establishing structural and microstructural properties of the maghemite phase of the IONPs, we built a maghemite model functionalized with aminoalkoxysilane, a molecule used to anchor (bio)molecules to oxide surfaces. By a linear response theory approach, we reveal that a resonance mechanism is responsible for the heat transfer from the IONPs to the surroundings. Heat transfer occurs not only via covalent linkages with the IONP but also through the solvent hydrogen-bond network. This result may pave the way to exploit the directional control of the heat flow from the IONPs to the anchored molecules-i.e., antibiotics, therapeutics, and enzymes-for their activation or release in a broader range of medical and industrial applications.

Multienzyme Redox System with Cofactor Regeneration for Cyclic Deracemization of Sulfoxides

Optically pure sulfoxides are noteworthy compounds applied in a wide range of industrial fields; however, the biocatalytic deracemization of racemic sulfoxides is challenging. Herein, a high-enantioselective methionine sulfoxide reductase A (MsrA) was combined with a low-enantioselective styrene monooxygenase (SMO) for the cyclic deracemization of sulfoxides. Enantiopure sulfoxides were obtained in >90% yield and with >90% enantiomeric excess ( ee ) through dynamic "selective reduction and non-selective oxidation" cycles. The cofactors of MsrA and SMO were subsequently regenerated by the cascade catalysis of three auxiliary enzymes through the consumption of low-cost D-glucose. Moreover, this "one-pot, one-step" cyclic deracemization strategy exhibited a wide substrate scope toward various aromatic, heteroaromatic, alkyl and thio-alkyl sulfoxides. This system proposed an efficient strategy for the green synthesis of chiral sulfoxide .

The Osteoinductivity of Calcium Phosphate-Based Biomaterials: A Tight Interaction With Bone Healing

Calcium phosphate (CaP)-based bioceramics are the most widely used synthetic biomaterials for reconstructing damaged bone. Accompanied by bone healing process, implanted materials are gradually degraded while bone ultimately returns to its original geometry and function. In this progress report, we reviewed the complex and tight relationship between the bone healing response and CaP-based biomaterials, with the emphasis on the in vivo degradation mechanisms of such material and their osteoinductive properties mediated by immune responses, osteoclastogenesis and osteoblasts. A deep understanding of the interaction between biological healing process and biomaterials will optimize the design of CaP-based biomaterials, and further translate into effective strategies for biomaterials customization.

Inhibitory effects of Moringa oleifera leaves extract on xanthine oxidase activity from bovine milk

Moringa oleifera is a tropical plant in the Moringaceae family that contains a lot of bioactive compounds. This study aimed to isolate and characterize the enzyme xanthine oxidase (XO), and conducted inhibitory tests on XO using methanol extracts of M. oleifera leaves. The xanthine oxidase enzyme isolated from bovine milk was characterized to determine the optimum pH, temperature, and substrate concentration. XO inhibition was evaluated by in vitro and in silico methods. The results of XO isolation and characterization of bovine milk showed the optimum conditions at pH 6.5, substrate concentration of 0.1 mM, and temperature 35 °C with an activity rate of 32.47 mU/mL; 21.55 mU/mL, and 21.94 mU/mL. Inhibition analysis results on methanol extract of M. oleifera leaves showed the highest activity decrease at the extract concentration of 160 ppm, with a relative inhibition value of 21.35%, while allopurinol as a positive control has a relative value inhibition of 61.21%. Relative value inhibition indicated the potential of M. oleifera leaves as a source of medicinal plants for gout sufferers. Additionally, a computational analysis was performed to observe the molecular interaction between the primary compounds of M. oleifera leaves, i.e., 5-O-acetyl-thio-octyl-β-L-rhamnofuranoside, quinic acid, and 2-dimethyl(trimethylsilylmethyl)silyloxymethyltetrahydrofuran, and XO using the molecular docking method. The finding implied that these compounds are bound to the catalytic sites of XO by hydrogen bonds and hydrophobic interactions, indicating the primary compounds of M. oleifera leaves could become XO inhibitors to treat gout disease.

Metal-responsive regulation of enzyme catalysis using genetically encoded chemical switches

Dynamic control over protein function is a central challenge in synthetic biology. To address this challenge, we describe the development of an integrated computational and experimental workflow to incorporate a metal-responsive chemical switch into proteins. Pairs of bipyridinylalanine (BpyAla) residues are genetically encoded into two structurally distinct enzymes, a serine protease and firefly luciferase, so that metal coordination biases the conformations of these enzymes, leading to reversible control of activity. Computational analysis and molecular dynamics simulations are used to rationally guide BpyAla placement, significantly reducing experimental workload, and cell-free protein synthesis coupled with high-throughput experimentation enable rapid prototyping of variants. Ultimately, this strategy yields enzymes with a robust 20-fold dynamic range in response to divalent metal salts over 24 on/off switches, demonstrating the potential of this approach. We envision that this strategy of genetically encoding chemical switches into enzymes will complement other protein engineering and synthetic biology efforts, enabling new opportunities for applications where precise regulation of protein function is critical.

A guide to designing photocontrol in proteins: methods, strategies and applications

Light is essential for various biochemical processes in all domains of life. In its presence certain proteins inside a cell are excited, which either stimulates or inhibits subsequent cellular processes. The artificial photocontrol of specifically proteins is of growing interest for the investigation of scientific questions on the organismal, cellular and molecular level as well as for the development of medicinal drugs or biocatalytic tools. For the targeted design of photocontrol in proteins, three major methods have been developed over the last decades, which employ either chemical engineering of small-molecule photosensitive effectors (photopharmacology), incorporation of photoactive non-canonical amino acids by genetic code expansion (photoxenoprotein engineering), or fusion with photoreactive biological modules (hybrid protein optogenetics). This review compares the different methods as well as their strategies and current applications for the light-regulation of proteins and provides background information useful for the implementation of each technique.

Stimuli-Responsive Regulation of Biocatalysis through Metallic Nanoparticle Interaction

The remote control of biocatalytic processes in an extracellular medium is an exciting idea to deliver innovative solutions in the biocatalysis field. With this purpose, metallic nanoparticles (NPs) are great candidates, as their inherent thermal, electric, magnetic, and plasmonic properties can readily be manipulated upon external stimuli. Exploring the unique NP properties beyond an anchoring platform for enzymes brings up the opportunity to extend the efficiency of biocatalysts and modulate their activity through triggered events. In this review, we discuss a set of external stimuli, such as light, electricity, magnetism, and temperature, as tools for the regulation of nanobiocatalysis, including the challenges and perspectives regarding their use. In addition, we elaborate on the use of combined stimuli that create a more refined framework in terms of a multiresponsive system. Finally, we envision this review might instigate researchers in this field of study with a set of promising opportunities in the near future.

Cellulase production and efficient saccharification of biomass by a new mutant Trichoderma afroharzianum MEA-12

BACKGROUND

Cellulase plays a key role in converting cellulosic biomass into fermentable sugar to produce chemicals and fuels, which is generally produced by filamentous fungi. However, most of the filamentous fungi obtained by natural breeding have low secretory capacity in cellulase production, which are far from meeting the requirements of industrial production. Random mutagenesis combined with adaptive laboratory evolution (ALE) strategy is an effective method to increase the production of fungal enzymes.

RESULTS

This study obtained a mutant of Trichoderma afroharzianum by exposures to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), Ethyl Methanesulfonate (EMS), Atmospheric and Room Temperature Plasma (ARTP) and ALE with high sugar stress. The T. afroharzianum mutant MEA-12 produced 0.60, 5.47, 0.31 and 2.17 IU/mL FPase, CMCase, pNPCase and pNPGase, respectively. These levels were 4.33, 6.37, 4.92 and 4.15 times higher than those of the parental strain, respectively. Also, it was found that T. afroharzianum had the same carbon catabolite repression (CCR) effect as other Trichoderma in liquid submerged fermentation. In contrast, the mutant MEA-12 can tolerate the inhibition of glucose (up to 20 mM) without affecting enzyme production under inducing conditions. Interestingly, crude enzyme from MEA-12 showed high enzymatic hydrolysis efficiency against three different biomasses (cornstalk, bamboo and reed), when combined with cellulase from T. reesei Rut-C30. In addition, the factors that improved cellulase production by MEA-12 were clarified.

CONCLUSIONS

Overall, compound mutagenesis combined with ALE effectively increased the production of fungal cellulase. A super-producing mutant MEA-12 was obtained, and its cellulase could hydrolyze common biomasses efficiently, in combination with enzymes derived from model strain T. reesei, which provides a new choice for processing of bioresources in the future.

Advances in Injectable In Situ-Forming Hydrogels for Intratumoral Treatment

Chemotherapy has been linked to a variety of severe side effects, and the bioavailability of current chemotherapeutic agents is generally low, which decreases their effectiveness. Therefore, there is an ongoing effort to develop drug delivery systems to increase the bioavailability of these agents and minimize their side effects. Among these, intratumoral injections using in situ-forming hydrogels can improve drugs' bioavailability and minimize drugs' accumulation in non-target organs or tissues. This review describes different types of injectable in situ-forming hydrogels and their intratumoral injection for cancer treatment, after which we discuss the antitumor effects of intratumoral injection of drug-loaded hydrogels. This review concludes with perspectives on the future applicability of, and challenges for, the adoption of this drug delivery technology.

Modulation of Transaminase Activity by Encapsulation in Temperature-Sensitive Poly(N-acryloyl glycinamide) Hydrogels

Smart hydrogels hold much potential for biocatalysis, not only for the immobilization of enzymes, but also for the control of enzyme activity. We investigated upper critical solution temperature‐type poly N‐acryloyl glycinamide (pNAGA) hydrogels as a smart matrix for the amine transaminase from Bacillus megaterium (BmTA). Physical entrapment of BmTA in pNAGA hydrogels results in high immobilization efficiency (>89 %) and high activity (97 %). The temperature‐sensitiveness of pNAGA is preserved upon immobilization of BmTA and shows a gradual deswelling upon temperature reduction. While enzyme activity is mainly controlled by temperature, deactivation tended to be higher for immobilized BmTA (≈62–68 %) than for free BmTA (≈44 %), suggesting a deactivating effect due to deswelling of the pNAGA gel. Although the deactivation in response to hydrogel deswelling is not yet suitable for controlling enzyme activity sufficiently, it is nevertheless a good starting point for further optimization.

Getting the Most Out of Enzyme Cascades: Strategies to Optimize In Vitro Multi-Enzymatic Reactions

In vitro enzyme cascades possess great benefits, such as their synthetic capabilities for complex molecules, no need for intermediate isolation, and the shift of unfavorable equilibria towards the products. Their performance, however, can be impaired by, for example, destabilizing or inhibitory interactions between the cascade components or incongruous reaction conditions. The optimization of such systems is therefore often inevitable but not an easy task. Many parameters such as the design of the synthesis route, the choice of enzymes, reaction conditions, or process design can alter the performance of an in vitro enzymatic cascade. Many strategies to tackle this complex task exist, ranging from experimental to in silico approaches and combinations of both. This review collates examples of various optimization strategies and their success. The feasibility of optimization goals, the influence of certain parameters and the usage of algorithm-based optimizations are discussed.

Switchable Biocatalytic Reactions Controlled by Interfacial pH Changes Produced by Orthogonal Biocatalytic Processes

Enzymes immobilized on a nano-structured surface were used to switch the activity of one enzyme by a local pH change produced by another enzyme. Immobilized amyloglucosidase (AMG) and trypsin were studied as examples of the pH-dependent switchable "target enzymes." The reactions catalyzed by co-immobilized urease or esterase were increasing or decreasing the local pH, respectively, thus operating as "actuator enzymes." Both kinds of the enzymes, producing local pH changes and changing biocatalytic activity with the pH variation, were orthogonal in terms of the biocatalytic reactions; however, their operation was coupled with the local pH produced near the surface with the immobilized enzymes. The "target enzymes" (AMG and trypsin) were changed reversibly between the active and inactive states by applying input signals (urea or ester, substrates for the urease or esterase operating as the "actuator enzymes") and washing them out with a new portion of the background solution. The developed approach can potentially lead to switchable operation of several enzymes, while some of them are inhibited when the others are activated upon receiving external signals processed by the "actuator enzymes." More complex systems with branched biocatalytic cascades can be controlled by orthogonal biocatalytic reactions activating selected pathways and changing the final output.

Reversible Photoswitchable Inhibitors Generate Ultrasensitivity in Out-of-Equilibrium Enzymatic Reactions

Ultrasensitivity is a ubiquitous emergent property of biochemical reaction networks. The design and construction of synthetic reaction networks exhibiting ultrasensitivity has been challenging, but would greatly expand the potential properties of life-like materials. Herein, we exploit a general and modular strategy to reversibly regulate the activity of enzymes using light and show how ultrasensitivity arises in simple out-of-equilibrium enzymatic systems upon incorporation of reversible photoswitchable inhibitors (PIs). Utilizing a chromophore/warhead strategy, PIs of the protease α-chymotrypsin were synthesized, which led to the discovery of inhibitors with large differences in inhibition constants (K_i) for the different photoisomers. A microfluidic flow setup was used to study enzymatic reactions under out-of-equilibrium conditions by continuous addition and removal of reagents. Upon irradiation of the continuously stirred tank reactor with different light pulse sequences, i.e., varying the pulse duration or frequency of UV and blue light irradiation, reversible switching between photoisomers resulted in ultrasensitive responses in enzymatic activity as well as frequency filtering of input signals. This general and modular strategy enables reversible and tunable control over the kinetic rates of individual enzyme-catalyzed reactions and makes a programmable linkage of enzymes to a wide range of network topologies feasible.

Responsive Emulsions for Sequential Multienzyme Cascades

Multienzyme cascade biocatalysis is an efficient synthetic process, avoiding the isolation/purification of intermediates and shifting the reaction equilibrium to the product side.. However, multienzyme systems are often limited by their incompatibility and cross-reactivity. Herein, we report a multi-responsive emulsion to proceed multienzyme reactions sequentially for high reactivity. The emulsion is achieved using a CO2 , pH, and thermo-responsive block copolymer as a stabilizer, allowing the on-demand control of emulsion morphology and phase composition. Applying this system to a three-step cascade reaction enables the individual optimal condition for each enzyme, and a high overall conversion (ca. 97 % of the calculated limit) is thereby obtained. Moreover, the multi-responsiveness of the emulsion allows the facile and separate yielding/recycling of products, polymers and active enzymes. Besides, the system could be scaled up with a good yield.

Magneto-Controlled Enzyme Activity with Locally Produced pH Changes

Biocatalytic activity of amyloglucosidase (AMG), immobilized on superparamagnetic nanoparticles, is dynamically and reversibly activated or inhibited by applying a magnetic field. The magnetic field triggers aggregation/deaggregation of magnetic particles that are also functionalized with urease or esterase enzymes. These enzymes produce a local pH change in the vicinity of the particles changing the AMG activity.

Development of a Cofactor Balanced, Multi Enzymatic Cascade Reaction for the Simultaneous Production of L-Alanine and L-Serine from 2-Keto-3-deoxy-gluconate

Enzymatic reaction cascades represent a powerful tool to convert biogenic resources into valuable chemicals for fuel and commodity markets. Sugars and their breakdown products constitute a significant group of possible substrates for such biocatalytic conversion strategies to value-added products. However, one major drawback of sugar cascades is the need for cofactor recycling without using additional enzymes and/or creating unwanted by-products. Here, we describe a novel, multi-enzymatic reaction cascade for the one-pot simultaneous synthesis of L-alanine and L-serine, using the sugar degradation product 2-keto-3-deoxygluconate and ammonium as precursors. To pursue this aim, we used four different, thermostable enzymes, while the necessary cofactor NADH is recycled entirely self-sufficiently. Buffer and pH optimisation in combination with an enzyme titration study yielded an optimised production of 21.3 +/− 1.0 mM L-alanine and 8.9 +/− 0.4 mM L-serine in one pot after 21 h.

Full Thermal Switching of Enzymes by Thermoresponsive Poly(2-oxazoline)-Based Enzyme Inhibitors

Controlling the activity of enzymes is an important feature for many processes in medicine, bioanalytics, and biotechnology. So far, it has not been possible to fully switch biocatalysts on and off by thermoresponsive enzyme inhibitors. Herein, we present poly(2-oxazoline)s with iminodiacetic acid end groups (POx-IDA) that are lower critical solution temperature (LCST) polymers and thus thermosensitive. They are capable of reversibly inhibiting the activity of horse radish peroxidase and laccase by more than 99 %. Increasing the temperature makes the POx-IDA precipitate, which leads to 100 % recovery of the enzyme activity. This switching cycle is fully reversible. The LCST of the POx-IDA can be tuned by varying the polymer composition to generate a wide range of switching windows.

Versatile Nanoplatforms with enhanced Photodynamic Therapy: Designs and Applications

As an emerging antitumor strategy, photodynamic therapy (PDT) has attracted intensive attention for the treatment of various malignant tumors owing to its noninvasive nature and high spatial selectivity in recent years. However, the therapeutic effect is unsatisfactory on some occasions due to the presence of some unfavorable factors including nonspecific accumulation of PS towards malignant tissues, the lack of endogenous oxygen in tumors, as well as the limited light penetration depth, further hampering practical application. To circumvent these limitations and improve real utilization efficiency, various enhanced strategies have been developed and explored during the past years. In this review, we give an overview of the state-of-the-art advances progress on versatile nanoplatforms for enhanced PDT considering the enhancement from targeting or responsive, chemical and physical effect. Specifically, these effects mainly include organelle-targeting function, tumor microenvironment responsive release photosensitizers (PS), self-sufficient O2 (affinity oxygen and generating oxygen), photocatalytic water splitting, X-rays light stimulate, surface plasmon resonance enhancement, and the improvement by resonance energy transfer. When utilizing these strategies to improve the therapeutic effect, the advantages and limitations are addressed. Finally, the challenges and prospective will be discussed and demonstrated for the future development of advanced PDT with enhanced efficacy.

Thermomagneto-Responsive Smart Biocatalysts for Malonyl-Coenzyme A Synthesis

Smart biocatalysts, in which enzymes are conjugated to stimuli-responsive polymers, have gained considerable attention because of their catalytic switchability and recyclability. Although many systems have been developed, they require separate laboratory techniques for their recovery, making them unsuitable for many practical applications. To address these issues, we designed a thermomagneto-responsive biocatalyst by immobilizing an enzyme on the terminal of thermo-responsive polymer brushes tethered on magnetic nanoparticle (NP) clusters. The concept is demonstrated by a system consisting of iron oxide NPs, poly(N-isopropyl-acrylamide), and a malonyl-Coenzyme A synthetase (MatB). By using free malonate and coenzyme A (CoA), the designed catalyst exhibits adequate activity for the production of malonyl-CoA. Thanks to the use of a magnetic NP cluster, whose magnetic moment is high, this system is fully recoverable under the magnetic field at above 32 °C because of the collapse of the thermo-responsive polymer shell in the clusters. In addition, the recycled catalyst maintains moderate activity even after three cycles, and it also shows excellent catalytic switchability, that is, negligible catalytic activity at 25 °C because of the blockage of the active sites of the enzyme by the extended hydrophilic polymer chains but great catalytic activity at a temperatures above the lower critical solution temperature at which the enzymes are exposed to the reaction medium because of the thermo-responsive contraction of polymer chains. Because the azide functionality in our system can be easily functionalized depending upon our need, such catalytically switchable, fully recoverable, and recyclable multiresponsive catalytic systems can be of high relevance for other cell-free biosynthetic approaches.

Benchtop NMR for Online Reaction Monitoring of the Biocatalytic Synthesis of Aromatic Amino Alcohols

Online analytics provides insights into the progress of an ongoing reaction without the need for extensive sampling and offline analysis. In this study, we investigated benchtop NMR as an online reaction monitoring tool for complex enzyme cascade reactions. Online NMR was used to monitor a two-step cascade beginning with an aromatic aldehyde and leading to an aromatic amino alcohol as the final product, applying two different enzymes and a variety of co-substrates and intermediates. Benchtop NMR enabled the concentration of the reaction components to be detected in buffered systems in the single-digit mM range without using deuterated solvent. The concentrations determined via NMR were correlated with offline samples analyzed via uHPLC and displayed a good correlation between the two methods. In summary, benchtop NMR proved to be a sensitive, selective and reliable method for online reaction monitoring in (multi-step) biosynthesis. In future, online analytic systems such as the benchtop NMR devices described might not only enable direct monitoring of the reaction, but may also form the basis for self-regulation in biocatalytic reactions.

A Multi-Enzymatic Cascade Reaction for the Synthesis of Vidarabine 5′-Monophosphate

We here described a three-step multi-enzymatic reaction for the one-pot synthesis of vidarabine 5′-monophosphate (araA-MP), an antiviral drug, using arabinosyluracil (araU), adenine (Ade), and adenosine triphosphate (ATP) as precursors. To this aim, three enzymes involved in the biosynthesis of nucleosides and nucleotides were used in a cascade mode after immobilization: uridine phosphorylase from Clostridium perfringens (CpUP), a purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNP), and deoxyadenosine kinase from Dictyostelium discoideum (DddAK). Specifically, CpUP catalyzes the phosphorolysis of araU thus generating uracil and α-d-arabinose-1-phosphate. AhPNP catalyzes the coupling between this latter compound and Ade to form araA (vidarabine). This nucleoside becomes the substrate of DddAK, which produces the 5′-mononucleotide counterpart (araA-MP) using ATP as the phosphate donor. Reaction conditions (i.e., medium, temperature, immobilization carriers) and biocatalyst stability have been balanced to achieve the highest conversion of vidarabine 5′-monophosphate (≥95.5%). The combination of the nucleoside phosphorylases twosome with deoxyadenosine kinase in a one-pot cascade allowed (i) a complete shift in the equilibrium-controlled synthesis of the nucleoside towards the product formation; and (ii) to overcome the solubility constraints of araA in aqueous medium, thus providing a new route to the highly productive synthesis of araA-MP.