Enzymatic Cascade Reactions Mediated by Highly Efficient Biomimetic Quasi Metal-Organic Frameworks

Tailored chitosan integration in diatomaceous earth particles as a scaffold for fructosyltransferase immobilization in fructo-oligosaccharide production

BACKGROUND

Fructo-oligosaccharide (FOS) belongs to the group of short inulin-type fructans and is one of the most important non-digestible bifid-oligosaccharides capable of biotransforming sucrose using fructosyltransferase (FTase). However, there are no immobilized FTase products that can be successfully used industrially. In this study, diatomite was subjected to extrusion, sintering and granulation to form diatomaceous earth particles that were further modified via chitosan aminomethylation for modification. FTase derived from Aspergillus oryzae was successfully immobilized on the modified support via covalent binding.

RESULTS

The immobilized enzyme activity was 503 IU g-1 at an enzyme concentration of 0.6 mg mL-1, immobilization pH of 7.0 and contact time of 3 h. Additionally, the immobilization yield was 56.91%. Notably, the immobilized enzyme was more stable under acidic conditions. Moreover, the half-life of the immobilized enzyme was 20.80 and 10.96 times as long as that of the free enzyme at 45 and 60 °C, respectively. The results show good reusability, as evidenced by the 84.77% retention of original enzyme activity after eight cycles. Additionally, the column transit time of the substrate was 35.56 min when the immobilized enzyme was applied in a packed-bed reactor. Furthermore, a consistently high FOS production yield of 60.68% was achieved and maintained over the 15-day monitoring period.

CONCLUSIONS

Our results suggest that immobilized FTase is a viable candidate for continuous FOS production on an industrial scale. © 2024 Society of Chemical Industry.

Neutrophil-Mimicking Nanozyme with Cascade Catalytic Releasing Nitric Oxide and Signet Oxygen Property for Synergistic Bimodal Therapy of Methicillin-Resistant Staphylococcus Aureus Infections

Recently, chloroperoxidase (CPO)-mediated enzyme dynamic therapy (EDT) by mimicking the antipathogen function of neutrophils via generating highly active signet oxygen (1O2) has attracted great interest in biomedical applications. However, the therapeutic efficiency of EDT is largely restricted by the low CPO delivery efficiency and insufficient hydrogen peroxide (H2O2) supply. In the present work, a neutrophil-mimicking nanozyme of MGBC with high CPO delivery efficiency, H2O2 self-supply, and enzyme-cascade catalytic properties is designed for high-efficient treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. In the infection microenvironment, MGBC can effectively catalyze glucose to self-supply substantial H2O2, which enables long-lasting 1O2 generation via the CPO-mediated catalytic reaction. At the meantime, MGBC can also catalyze H2O2 to sustainably release NO for gas therapy (GT), which synergistically strengthens the therapeutic effect of EDT. As a result, MGBC displayed effective MRSA-killing and MSRA biofilms-eradicating properties, and high efficiency in treating both MRSA infected full-thickness excision wounds and subcutaneous MRSA infection by exerting the synergistic bimodal EDT/GT therapeutic effects. In-depth mechanism study revealed that the synergistic EDT/GT antibacterial effects of MGBC can attenuate the drug resistance and toxicity of MRSA by significantly downregulating quorum sensing, multidrug efflux, virulence, and biofilm formation-related genes.

Confinement-Induced Biocatalytic Activity Enhancement of Light- and Thermoresponsive Polymer@Enzyme@MOF Composites

Metal-organic frameworks (MOFs) are favorable hosting materials for fixing enzymes to construct enzyme@MOF composites and to expand the applications of biocatalysts. However, the rigid structure of MOFs without tunable hollow voids and a confinement effect often limits their catalytic activities. Taking advantage of the smart soft polymers to overcome the limitation, herein, a protection protocol to encapsulate the enzyme in zeolitic imidazolate framework-8 (ZIF-8) was developed using a glutathione-sensitive liposome (L) as a soft template. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were first anchored on a light- and thermoresponsive porous poly(styrene-maleic anhydride-N,N-dimethylaminoethyl methacrylate-spiropyran) membrane (PSMDSP) to produce PSMDSP@GOx-HRP, which could provide a confinement effect by switching the UV irradiation or varying the temperature. Afterward, embedding PSMDSP@GOx-HRP in L and encapsulating PSMDSP@GOx-HRP@L into hollow ZIF-8 (HZIF-8) to form PSMDSP@GOx-HRP@HZIF-8 composites were performed, which proceeded during the crystallization of the framework following the removal of L by adding glutathione. Impressively, the biocatalytic activity of the composites was 4.45-fold higher than that of the free enzyme under UV irradiation at 47 °C, which could benefit from the confinement effect of PSMDSP and the conformational freedom of the enzyme in HZIF-8. The proposed composites contributed to the protection of the enzyme against harsh conditions and exhibited superior stability. Furthermore, a colorimetric assay based on the composites for the detection of serum glucose was established with a linearity range of 0.05-5.0 mM, and the calculated LOD value was 0.001 mM in a cascade reaction system. This work provides a universal design idea and a versatile technique to immobilize enzymes on soft polymer membranes that can be encapsulated in porous rigid MOF-hosts. It also holds potential for the development of smart polymer@enzyme@HMOFs biocatalysts with a tunable confinement effect and high catalytic performance.

GAA/(Au-Au/IrO2)@Cu(PABA) reactor with cascade catalytic activity for α-glucosidase inhibitor screening

BACKGROUND

In vitro screening strategies based on the inhibition of α-glucosidase (GAA) activity have been widely used for the discovery of potential antidiabetic drugs, but they still face some challenges, such as poor enzyme stability, non-reusability and narrow range of applicability. To overcome these limitations, an in vitro screening method based on GAA@GOx@Cu-MOF reactor was developed in our previous study. However, the method was still not satisfactory enough in terms of construction cost, pH stability, organic solvent resistance and reusability. Thence, there is still a great need for the development of in vitro screening methods with lower cost and wider applicability.

RESULTS

A colorimetric sensing strategy based on GAA/(Au-Au/IrO2)@Cu(PABA) cascade catalytic reactor, which constructed through simultaneous encapsulating Au-Au/IrO2 nanozyme with glucose oxidase-mimicking and peroxidase-mimicking activities and GAA in Cu(PABA) carrier with peroxidase-mimicking activity, was innovatively developed for in vitro screening of GAA inhibitors in this work. It was found that the reactor not only exhibited excellent thermal stability, pH stability, organic solvent resistance, room temperature storage stability, and reusability, but also possessed cascade catalytic performance, with approximately 12.36-fold increased catalytic activity compared to the free system (GAA + Au-Au/IrO2). Moreover, the in vitro GAA inhibitors screening method based on this reactor demonstrated considerable anti-interference performance and detection sensitivity, with a detection limit of 4.79 nM for acarbose. Meanwhile, the method owned good reliability and accuracy, and has been successfully applied to the in vitro screening of oleanolic acid derivatives as potential GAA inhibitors.

SIGNIFICANCE

This method not only more effectively solved the shortcomings of poor stability, narrow scope of application, and non-reusability of natural enzymes in the classical method compared with our previous work, but also broaden the application scope of Au-Au/IrO2 nanozyme with glucose oxidase and peroxidase mimicking activities, and Cu(PABA) carrier with peroxidase mimicking activity, which was expected to be a new generation candidate method for GAA inhibitor screening.

Metal-Organic Framework Induced Stabilization of Proteins in Polymeric Nanoparticles

Developing protein confinement platforms is an attractive research area that not only promotes protein delivery but also can result in artificial environment mimicking of the cellular one, impacting both the controlled release of proteins and the fundamental protein biophysics. Polymeric nanoparticles (PNPs) are attractive platforms to confine proteins due to their superior biocompatibility, low cytotoxicity, and controllable release under external stimuli. However, loading proteins into PNPs can be challenging due to the potential protein structural perturbation upon contacting the interior of PNPs. In this work, we developed a novel approach to encapsulate proteins in PNPs with the assistance of the zeolitic imidazolate framework (ZIF). Here, ZIF offers an additional protection layer to the target protein by forming the protein@ZIF composite via aqueous-phase cocrystallization. We demonstrated our platform using a model protein, lysozyme, and a widely studied PNP composed of poly(ethylene glycol)-poly(lactic-co-glycolic acid) (PEG-PLGA). A comprehensive study via standard loading and release tests as well as various spectroscopic techniques was carried out on lysozyme loaded onto PEG-PLGA with and without ZIF protection. As compared with the direct protein encapsulation, an additional layer with ZIF prior to loading offered enhanced loading capacity, reduced leaching, especially in the initial stage, led to slower release kinetics, and reduced secondary structural perturbation. Meanwhile, the function, cytotoxicity, and cellular uptake of proteins encapsulated within the ZIF-bound systems are decent. Our results demonstrated the use of ZIF in assisting in protein encapsulation in PNPs and established the basis for developing more sophisticated protein encapsulation platforms using a combination of materials of diverse molecular architectures and disciplines. As such, we anticipate that the protein-encapsulated ZIF systems will serve as future polymer protein confinement and delivery platforms for both fundamental biophysics and biochemistry research and biomedical applications where protein delivery is needed to support therapeutics and/or nutrients.

Multienzyme cascades analysis of α-glucosidase by oxygen deficient MoO3-x

BACKGROUND

Recently, the enzymatic cascade reactions during the cellular process are widely used for fabricating robust biosensors and they have attracted extensive attention in analyzing various clinical biomarkers. The enzymatic cascades analysis is commonly based on the peroxidase (POD)/oxidase coupled system. However, the requirement of harsh acidic environment, poor stability and interference from the oxidase further limit their analytical practicability. Herein, novel chromogenic nanomaterials with H2O2 sensitive features are urgently required to replace the POD nanozyme in enzymatic cascades based bioanalysis.

RESULTS

Herein, oxygen deficient MoO3-x with H2O2 sensitive features and near-infrared (NIR) absorption band have been ultra-fast synthesized and utilized for the enzymatic cascades analysis of α-Glucosidase's activity, and inhibitors screening. With the addition of 4-nitrophenyl-α-d-glucopyranoside, the simultaneous presence of α-Glucosidase and glucose oxidase (GOx) would fade their dark blue color and decrease the NIR absorption. The α-Glucosidase's activity can be analyzed by the absorption at 770 nm, and their limit of detection is 8 × 10-5 U/mL, indicating the superior performance of the proposed colorimetric assay. Moreover, this proposed α-Glucosidase assay is further utilized for inhibitors screening. Moreover, the activity of α-Glucosidase can also be analyzed by the smartphone and microplate reader through the agarose-based colorimetric portable kit.

SIGNIFICANCE

This MoO3-x involved enzymatic cascades assay would facilitate for the development of bio-analysis related to H2O2 generation or consumption. Moreover, this bio-analysis strategy will contribute to the development of other H2O2 sensitive chromogenic nanomaterials for the analysis of certain biomolecules and biological enzymes.

Biomolecules meet organic frameworks: from synthesis strategies to diverse applications

Biomolecules are essential in pharmaceuticals, biocatalysts, biomaterials, etc., but unfortunately they are extremely susceptible to extraneous conditions. When biomolecules meet porous organic frameworks, significantly improved thermal, chemical, and mechanical stabilities are not only acquired for raw biomolecules, but also molecule sieving, substrate enrichment, chirality property, and other functionalities are additionally introduced for application expansions. In addition, the intriguing synergistic effect stemming from elaborate and concerted interactions between biomolecules and frameworks can further enhance application performances. In this paper, the synthesis strategies of the so-called bio-organic frameworks (BOFs) in recent years are systematically reviewed and classified. Additionally, their broad applications in biomedicine, catalysis, separation, sensing, and imaging are introduced and discussed. Before ending, the current challenges and prospects in the future for this infancy-stage but significant research field are also provided. We hope that this review will offer a concise but comprehensive vision of designing and constructing multifunctional BOF materials as well as their full explorations in various fields.

Detection of acrylamide in food based on MIL-glucose oxidase cascade colorimetric aptasensor

BACKGROUND

Maillard reaction involves the polymerization, condensation, and other reactions between compounds containing free amino groups and reducing sugars or carbonyl compounds during heat processing. This process endows unique flavors and colors to food, while it can also produce numerous hazards. Acrylamide (AAm) is one of Maillard's hazards with neurotoxicity and carcinogenicity, these effects can trigger mutations and alternations in gene expression in human cells and accelerate organ aging. An accurate and reliable acrylamide detection method with high sensitivity and specificity for future regulatory activities is urgently needed.

RESULTS

Herein, we constructed a colorimetric aptasensor with the hybridization of MIL-glucose oxidase (MGzyme)-cDNA and magnetic nanoparticle-aptamer (MNP-Apt) to specifically detect AAm. The incorporation of MB-Apt and AAm released MGzyme-cDNA in the supernatant, took the supernatant out, with the addition of glucose and TMB, MGzyme would oxidize glucose, the resulting •OH facilitated the oxidation of colorless TMB to blue ox-TMB. The absorbance value at 652 nm, which indicates the characteristic absorption peak of ox-TMB, exhibited a proportion to the concentration of AAm. MGzyme avoided the addition of harmful intermediate H2O2 and created an acid microenvironment for the catalytic reaction. MNP-Apt possessed the advantages of high specificity and simplified separation. Under optimal conditions, this method displayed a linear range of 0.01-100 μM with the limit of detection of 1.53 nM. With the spiked analysis data cross-verified by ELISA kit, this aptasensor was proven to specifically detect AAm at low concentrations.

SIGNIFICANCE

This colorimetric aptasensor was the integration of aptamer and the enzyme-cascade system, which could broaden the applicable range of enzyme-cascade system, break the limits of specific detection of substrates, eliminate the need for harmful intermediates, improve the reaction efficiency, implement the specific detection, whilst enabling the accurate detection of AAm. Given these remarkable performances, this method has shown significant potential in the field of food safety inspection.

Nano- and Microscale Confinements in DNA-Scaffolded Enzyme Cascade Reactions

Artificial reconstruction of naturally evolved principles, such as compartmentalization and cascading of multienzyme complexes, offers enormous potential for the development of biocatalytic materials and processes. Due to their unique addressability at the nanoscale, DNA origami nanostructures (DON) have proven to be an exceptionally powerful tool for studying the fundamental processes in biocatalytic cascades. To systematically investigate the diffusion-reaction network of (co)substrate transfer in enzyme cascades, a model system of stereoselective ketoreductase (KRED) with cofactor regenerating enzyme is assembled in different spatial arrangements on DNA nanostructures and is located in the sphere of microbeads (MB) as a spatially confining nano- and microenvironment, respectively. The results, obtained through the use of highly sensitive analytical methods, Western blot-based quantification of the enzymes, and mass spectrometric (MS) product detection, along with theoretical modeling, provide strong evidence for the presence of two interacting compartments, the diffusion layers around the microbead and the DNA scaffold, which influence the catalytic efficiency of the cascade. It is shown that the microscale compartment exerts a strong influence on the productivity of the cascade, whereas the nanoscale arrangement of enzymes has no influence but can be modulated by the insertion of a diffusion barrier.

Enzyme Cascade Electrode Reactions with Nanomaterials and Their Applicability towards Biosensor and Biofuel Cells

Nanomaterials, including carbon nanotubes, graphene oxide, metal-organic frameworks, metal nanoparticles, and porous carbon, play a crucial role as efficient carriers to enhance enzyme activity through substrate channeling while improving enzyme stability and reusability. However, there are significant debates surrounding aspects such as enzyme orientation, enzyme loading, retention of enzyme activity, and immobilization techniques. Consequently, these subjects have become the focus of intensive research in the realm of multi-enzyme cascade reactions. Researchers have undertaken the challenge of creating functional in vitro multi-enzyme systems, drawing inspiration from natural multi-enzyme processes within living organisms. Substantial progress has been achieved in designing multi-step reactions that harness the synthetic capabilities of various enzymes, particularly in applications such as biomarker detection (e.g., biosensors) and the development of biofuel cells. This review provides an overview of recent developments in concurrent and sequential approaches involving two or more enzymes in sequence. It delves into the intricacies of multi-enzyme cascade reactions conducted on nanostructured electrodes, addressing both the challenges encountered and the innovative solutions devised in this field.

Metal-Organic Framework for the Immobilization of Oxidoreductase Enzymes: Scopes and Perspectives

Oxidoreductases are a wide class of enzymes that can catalyze biological oxidation and reduction reactions. Nowadays, oxidoreductases play a vital part in most bioenergetic metabolic pathways, which have important applications in biodegradation, bioremediation, environmental applications, as well as biosensors. However, free oxidoreductases are not stable and hard to be recycled. In addition, cofactors are needed in most oxidoreductases catalyze reactions, which are so expensive and unstable that it hinders their industrial applications. Enzyme immobilization is a feasible strategy that can overcome these problems. Recently, metal-organic frameworks (MOFs) have shown great potential as support materials for immobilizing enzymes due to their unique properties, such as high surface-area-to-volume ratio, chemical stability, functional designability, and tunable pore size. This review discussed the application of MOFs and their composites as immobilized carriers of oxidoreductase, as well as the application of MOFs as catalysts and immobilized carriers in redox reactions in the perspective of the function of MOFs materials. The paper also focuses on the potential of MOF carrier-based oxidoreductase immobilization for designing an enzyme cascade reaction system.

Opportunities and Challenges of Metal-Organic Framework Micro/Nano Reactors for Cascade Reactions

Building bridges among different types of catalysts to construct cascades is a highly worthwhile pursuit, such as chemo-, bio-, and chemo-bio cascade reactions. Cascade reactions can improve the reaction efficiency and selectivity while reducing steps of separation and purification, thereby promoting the development of "green chemistry". However, compatibility issues in cascade reactions pose significant constraints on the development of this field, particularly concerning the compatibility of diverse catalyst types, reaction conditions, and reaction rates. Metal-organic framework micro/nano reactors (MOF-MNRs) are porous crystalline materials formed by the self-assembly coordination of metal sites and organic ligands, possessing a periodic network structure. Due to the uniform pore size with the capability of controlling selective transfer of substances as well as protecting active substances and the organic-inorganic parts providing reactive microenvironment, MOF-MNRs have attracted significant attention in cascade reactions in recent years. In this Perspective, we first discuss how to address compatibility issues in cascade reactions using MOF-MNRs, including structural design and synthetic strategies. Then we summarize the research progress on MOF-MNRs in various cascade reactions. Finally, we analyze the challenges facing MOF-MNRs and potential breakthrough directions and opportunities for the future.

Orientation-Controllable Enzyme Cascade on Electrode for Bioelectrocatalytic Chain Reaction

The accomplishment of concurrent interenzyme chain reaction and direct electric communication in a multienzyme-electrode is challenging since the required condition of multienzymatic binding conformation is quite complex. In this study, an enzyme cascade-induced bioelectrocatalytic system has been constructed using solid binding peptide (SBP) as a molecular binder that coimmobilizes the invertase (INV) and flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenase gamma-alpha complex (GDHγα) cascade system on a single electrode surface. The SBP-fused enzyme cascade was strategically designed to induce diverse relative orientations of coupling enzymes while enabling efficient direct electron transfer (DET) at the FAD cofactor of GDHγα and the electrode interface. The interenzyme relative orientation was found to determine the intermediate delivery route and affect overall chain reaction efficiency. Moreover, interfacial DET between the fusion GDHγα and the electrode was altered by the binding conformation of the coimmobilized enzyme and fusion INVs. Collectively, this work emphasizes the importance of interenzyme orientation when incorporating enzymatic cascade in an electrocatalytic system and demonstrates the efficacy of SBP fusion technology as a generic tool for developing cascade-induced direct bioelectrocatalytic systems. The proposed approach is applicable to enzyme cascade-based bioelectronics such as biofuel cells, biosensors, and bioeletrosynthetic systems utilizing or producing complex biomolecules.

Co-immobilization of β-xylosidase and endoxylanase on zirconium based metal-organic frameworks for improving xylosidase activity at high temperature and in acetone

Improving the activity of β-xylosidase at high temperature and organic solvents is important for the conversion of xylan, phytochemicals and some hydroxyl-containing substances to produce xylose and bioactive substances. In this study, a β-xylosidase R333H and an endoxylanase were simultaneously co-immobilized on the metal-organic framework UiO-66-NH₂. Compared with the single R333H immobilization system, the co-immobilization enhanced the activity of R333H at high temperature and high concentration of acetone, and the relative activities at 95°C and 50% acetone solution were > 95%. The K_m value of co-immobilized R333H towards p-Nitrophenyl-β-D-xylopyranoside (pNPX) shifted from 2.04 to 0.94 mM, which indicated the enhanced affinity towards pNPX. After 5 cycles, the relative activities of the co-immobilized enzymes towards pNPX and corncob xylan were 52% and 70% respectively, and the accumulated amount of reducing sugars obtained by co-immobilized enzymes degrading corncob xylan in 30% (v/v) acetone solution was 1.7 times than that with no acetone.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Confined Cascade Metabolic Reprogramming Nanoreactor for Targeted Alcohol Detoxification and Alcoholic Liver Injury Management

Alcoholic liver injury (ALI) is the leading cause of serious liver disease, whereas current treatments are mostly supportive and unable to metabolize alcohol directly. Here we report a metabolic reprogramming strategy for targeted alcohol detoxification and ALI management based on a confined cascade nanoreactor. The nanoreactor (named AA@mMOF) is designed by assembling natural enzymes of alcohol oxidase (AOx) and aldehyde dehydrogenase (ALDH) in the cavity of a mesoporous metal organic framework (mMOF) nanozyme with intrinsic catalase (CAT)-like activity. By conducting confined AOx/CAT/ALDH cascade reactions, AA@mMOF enables self-accelerated alcohol degradation (>0.5 mg·mL^-1·h^-1) with negligible aldehyde diffusion and accumulation, reprogramming alcohol metabolism and allowing high-efficiency detoxification. Administered to high-dose alcohol-intoxicated mice, AA@mMOF shows surprising liver targeting and accumulation performance and dramatically reduces blood alcohol concentration and rapidly reverses unconsciousness and acute liver injury to afford targeted alcoholism treatment. Moreover, AA@mMOF dramatically alleviates fat accumulation and oxidative stress in the liver of chronic alcoholism mice to block and reverse the progression of ALI. By conducting confined AOx/CAT/ALDH cascade reactions for high-efficiency alcohol metabolism reprogramming, AA@mMOF nanoreactor offers a powerful modality for targeted alcohol detoxification and ALI management. The proposed confined cascade metabolic reprogramming strategy provides a paradigm shift for the treatment of metabolic diseases.

Molecular insights of nanozymes from design to catalytic mechanism

Emerging as cost-effective potential alternatives to natural enzymes, nanozymes have attracted increasing interest in broad fields. To exploit the in-depth potential of nanozymes, rational structural engineering and explicit catalytic mechanisms at the molecular scale are required. Recently, impressive progress has been made in mimicking the characteristics of natural enzymes by constructing metal active sites, binding pockets, scaffolds, and delicate allosteric regulation. Ingenious in-depth studies have been conducted with advances in structural characterization and theoretical calculations, unveiling the "black box" of nanozyme-catalytic mechanisms. This review introduces the state-of-art synthesis strategies by learning from the natural enzyme counterparts and summarizes the general overview of the nanozyme mechanism with a particular emphasis on the adsorbed intermediates and descriptors that predict the nanozyme activity The emerging activity assessment methodology that illustrates the relationship between electrochemical oxygen reduction and enzymatic oxygen reduction is discussed with up-to-date advances Future opportunities and challenges are presented in the end to spark more profound work and attract more researchers from various backgrounds to the flourishing field of nanozymes.

A Plurizyme with Transaminase and Hydrolase Activity Catalyzes Cascade Reactions

Engineering dual‐function single polypeptide catalysts with two abiotic or biotic catalytic entities (or combinations of both) supporting cascade reactions is becoming an important area of enzyme engineering and catalysis. Herein we present the development of a PluriZyme, TR₂E₂, with efficient native transaminase (k_cat: 69.49±1.77 min⁻¹) and artificial esterase (k_cat: 3908–0.41 min⁻¹) activities integrated into a single scaffold, and evaluate its utility in a cascade reaction. TR₂E₂ (pH_opt: 8.0–9.5; T_opt: 60–65 °C) efficiently converts methyl 3‐oxo‐4‐(2,4,5‐trifluorophenyl)butanoate into 3‐(R)‐amino‐4‐(2,4,5‐trifluorophenyl)butanoic acid, a crucial intermediate for the synthesis of antidiabetic drugs. The reaction proceeds through the conversion of the β‐keto ester into the β‐keto acid at the hydrolytic site and subsequently into the β‐amino acid (e.e. >99 %) at the transaminase site. The catalytic power of the TR₂E₂PluriZyme was proven with a set of β‐keto esters, demonstrating the potential of such designs to address bioinspired cascade reactions.

Multienzyme Cascades Based on Highly Efficient Metal-Nitrogen-Carbon Nanozymes for Construction of Versatile Bioassays

Distinguished by the coupled catalysis-facilitated high turnover and admirable specificity, enzyme cascades have sparked tremendous attention in bioanalysis. However, three-enzyme cascade-based versatile platforms have rarely been explored without resorting to tedious immobilization procedures. Herein, we have demonstrated that formamide-converted transition metal-nitrogen-carbon (f-MNC, M = Fe, Cu, Mn, Co, Zn) with a high loading of atomically dispersed active sites possesses intrinsic peroxidase-mimetic activity following the activity order of f-FeNC > f-CuNC > f-MnNC > f-CoNC > f-ZnNC. Ulteriorly, benefitting from the greatest catalytic performance and explicit catalytic mechanism of f-FeNC, versatile enzyme cascade-based colorimetric bioassays for ultrasensitive detection of diabetes-related glucose and α-glucosidase (α-Glu) have been unprecedentedly devised using f-FeNC-triggered chromogenic reaction of 3,3',5,5'-tetramethylbenzidine as an amplifier. Notably, several types of α-Glu substrates can be effectively utilized in this three-enzyme cascade-based α-Glu assay, and it can be further employed for screening α-Glu inhibitors that are used as antidiabetic and antiviral drugs. These versatile assays can also be extended to detect other H₂O₂-generating or -consuming biomolecules and other bioenzymes that are capable of catalyzing glucose generation procedures. These nanozyme-involved multienzyme cascades without intricate enzyme-engineering techniques may provide a concept to facilitate the deployment of nanozymes in celestial versatile bioassay fabrication, disease diagnosis, and biomedicine.

Polyoxometalate-Based Metal-Organic Frameworks as the Solid Support to Immobilize MP-11 Enzyme for Enhancing Thermal and Recyclable Stability

The immobilization of enzymes has received much attention. Metal-organic framework (MOF) as the adsorbent for enzyme encapsulation provides an effective strategy. However, the encapsulation efficacy is not dependent solely on the specific surface area. Though leading into appropriate substrate with negative charge would enhance the encapsulation efficacy. Polyoxometalates (POMs) as the electron sponge would donate electrons without any structural change. In this study, Keggin-type phosphotungstic acid (PW₁₂) was encapsulated in Zirconium metal-organic framework (PW₁₂@UiO-67) as a heterogeneous adsorbent for the encapsulation of enzyme. Our following data proved that this composite cluster could enhance the adsorption of enzyme and the stability of MP-11 was then significantly improved after immobilization.

Ladder-Like DNA Nanostructure-Mediated Cascade Catalytic Nanomachine for Construction of Ultrasensitive Biosensors

Herein, a novel two-dimensional ladder-like DNA nanostructure (LDN)-mediated cascade catalytic nanomachine (LDN-CCN) with a higher catalytic efficiency beyond those of a conventional one-dimensional hybrid chain reaction (HCR) nanostructure-mediated CCN was constructed and applied to design an electrochemical biosensing platform with first-rank performance for ultrasensitive detection of target miRNA-21. First, output DNA S1' and S2' were produced through the DNAzyme recycle amplification when the target miRNA-21 existed. Then, the controllable LDN-CCN was constructed on S1-S2 modified electrodes by the subsequent reaction triggered by S1' and S2' with H1-AuNPs, H2, H3-AuNPs, and H4 with the assistance of K⁺ and hemin, in which the hemin/G-quadruplexes could produce a prominent electrochemical signal response to the substrate glucose. The best performance of cascade catalysis was acquired when the distance of Au nanoparticles (glucose oxidase-like activity) modified on H1 and H3 and hemin/G-quadruplexes (peroxidase-like activity) formed by the sticky ends of H2 and H4 was roughly 9 nm (27 bp) in LDN-CCN. The constructed electrochemical platform realized the sensitive detection of target miRNA-21 with the linear range from 100 aM to 10 nM and with a detection limit as low as 48.5 aM, which provided novel insights to explore the new functional DNA nanostructure and well-performing mimic enzyme cascade catalytic platforms for applications in biological fields and early diagnosis of diseases.

Fabrication of 3D Amino-Functionalized Metal-Organic Framework on Porous Nickel Foam Skeleton to Combinate Follicle Stimulating Hormone Antibody for Specific Recognition of Follicle-Stimulating Hormone

In this study, a superficial and highly efficient hydrothermal synthesis method was developed for the in situ growth of amine-functionalized iron containing metal-organic frameworks (H2N-Fe-MIL-101 MOFs) on porous nickel foam (NicF) skeletons (H2N-Fe-MIL-101/NicF). The uniform decoration of the H2N-Fe-MIL-101 nanosheets thus generated on NicF was immobilized with follicle-stimulating hormone (FSH) antibody (Ab-FSH) to detect FSH antigen. In the present work, the Ab-FSH tagged H2N-Fe-MIL-101/NicF electrode was first applied as an immunosensor for the recognition of FSH, electrochemically. With all of the special characteristics, this material demonstrated superior specific recognition and sensitivity for FSH with an estimated detection limit (LOD) of 11.6 and 11.5 fg/mL for buffered and serum solutions, respectively. The availability of specific functional groups on MOFs makes them an interesting choice for exploring molecular sensing applications utilizing Ab-FSH tagged biomolecules.

Construction of Metal Hydrate-Based Amorphous Magnetic Nanosheets for Enhanced Protein Enrichment and Immobilization

Inspired by the hierarchical fabrication technique, many self-assembly procedures have improved the construction of nanomaterials with unique physicochemical characteristics and multiple functions. The generation of multiple complexes is always accompanied by hierarchical structures and intriguing properties that are distinct from their individual segments. An interesting composite is amorphous magnetic Zn-Zr phosphate hydrated nanosheets (Zn-Zr APHNs), generated using templated synthesis and nanoparticle codeposition. The special porous structure of this construct, together with the abundance of metal ions and hydrate present, endows it with many interaction sites for proteins, provides high loading efficiency, and enhances bioactivity. Then, a series of proteins, including enzymes, was immobilized by the Zn-Zr APHNs by multiple interactions, high ionization, and larger surface of the nanosheets. In this study, novel methods for the enrichment of bioactive proteins while retaining the activity of protein payloads are presented. As a verification method, it is indicated that the Zn-Zr APHNs can deliver enzyme proteins (i.e., Cyt-c) to increase the catalytic activity with their biological function and structural integrity, resulting in a highly increased activity to free proteins.