Specific Ligation of Two Multimeric Enzymes with Native Peptides and Immobilization with Controlled Molar Ratio

Co-immobilization of galactose oxidase, catalase, and Mn-superoxide dismutase for efficient conversion of 5-hydroxymethylfurfural to 2,5-diformylfuran in water

The three enzymes galactose oxidase (GO), catalase (CAT), and Mn-superoxide dismutase (SOD) were simultaneously immobilized by coordinating to CuII in phosphate buffer saline. The biocatalyst GO&CAT&SOD@CuII was used for the conversion of 5-hydroxymethylfurfural (HMF). The immobilized GO catalyzes the oxidation of HMF to 2,5-diformylfuran (DFF), concomitantly the co-substrate O2 is reduced to hydrogen peroxide (H2O2). A portion of the byproduct H2O2 is broken down to O2 and H2O by the co-immobilized CAT, and the evolved O2 can be recycled and used as the co-substrate. A portion of the byproduct H2O2 is broken down to produce hydroxyl radicals •OH under the synergistic catalysis of the immobilized SOD and coordinated CuII, and the produced •OH can reactivate the immobilized galactose oxidase. Two aspects contribute to the high catalytic efficiency by GO&CAT&SOD@CuII: the reactivation of the immobilized galactose oxidase by producing •OH and the enrichment of the co-substate O2 by recycling the produced O2. For the conversion of 10 mM HMF, GO&CAT&SOD@CuII (with encapsulated GO 0.2 mg/mL) achieved 97% HMF conversion within 2 h reaction. In contrast, free galactose oxidase M3-5 variant (ACS Catalysis 2018, 8, 4025) (0.2 mg/mL) achieved 25.3% HMF conversion within 2 h reaction. All the reactions were carried out in pure water, not in PBS.

Multienzyme nanoassemblies: from rational design to biomedical applications

Multienzyme nanoassemblies (MENAs) that combine the functions of several enzymes into one entity have attracted widespread research interest due to their improved enzymatic performance and great potential for multiple applications. Considerable progress has been made to design and fabricate MENAs in recent years. This review begins with an introduction of the up-to-date strategies in designing MENAs, mainly including substrate channeling, compartmentalization and control of enzyme stoichiometry. The desirable properties that endow MENAs with important applications are also discussed in detail. Then, the recent advances in utilizing MENAs in the biomedical field are reviewed, with a particular focus on biosensing, tumor therapy, antioxidant and drug delivery. Finally, the challenges and perspectives for development of versatile MENAs are summarized.

Cobalt Phosphate Nanocrystals: A Catalase-Like Nanozyme and In Situ Enzyme-Encapsulating Carrier for Efficient Chemoenzymatic Synthesis of α-Keto Acid

Chemoenzymatic catalysis combining the traits of chemical and enzymatic catalysis provides tremendous possibilities for the design of biosynthetic pathways utilizing inorganic catalysts and enzymes. However, the efficiency of chemoenzymatic catalysis is usually governed by the synergy and compatibility of the two catalysts. Here, we report for the first time the catalase-like activity of cobalt phosphate nanocrystals (CoPs). By a one-pot biomimetic mineralization with CoPs and l-amino acid oxidase (LAAO) under a mild condition, we have fabricated a hybrid nanobiocatalyst, LAAO@CoPs, for the chemoenzymatic synthesis of α-keto acid. The as-fabricated nanobiocatalyst with directly contacted catalytic sites of the enzyme and nanozyme maximizes the substrate channeling effects for in situ chemical decomposition of the oxidative intermediate, H₂O₂, during the enzymatic oxidation of l-tryptophan (l-Trp), thus minimizing the H₂O₂ accumulation and byproduct generation. Benefiting from the superiority of LAAO@CoPs, complete conversion (100.0%) of l-Trp to indole pyruvic acid is achieved, over two times higher than the yield of the free LAAO system (47.6%). Meanwhile, LAAO@CoPs show high stabilities against heat and proteolytic treatments. This work offers a new design approach for constructing a high-performance nanobiocatalyst for cascade reactions, especially for those systems with toxic or reactive intermediates.

Coupling a recombinant oxidase to catalase through specific noncovalent interaction to improve the oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

5-Hydroxymethylfurfural oxidase (HMFO) can catalyze both hydroxyl and aldehyde oxidations. It catalyzes 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid. However, the application of HMFO encountered two problems: the expressed HMFO in Escherichia coli. is largely in the form of inclusion bodies, and the by-product of H₂O₂ has a negative effect on HMFO stability. To solve these problems, recombinant HMFO was generated by fusing the C-terminus to an elastin-like polypeptide (ELP). ELP-HMFO can be expressed with significantly reduced inclusion bodies. ELP-HMFO exhibited improved stability and tolerance toward H₂O₂. Further recombination is carried out by fusing the N-terminus of HMFO to a glutamic acid-rich leucine zipper motif (Z_E). Similarly, recombinant catalase (CAT) is generated by fusing the N-terminus to ELP and fusing the C-terminus to an arginine-rich leucine zipper motif (Z_R). ELP-HMFO-Z_E can interact specifically with Z_R-CAT-ELP, ascribing to the coiled-coil association of Z_E and Z_R. ELP-HMFO-Z_E#Z_R-CAT-ELP coordinates the respective catalytic activities of the two enzymes. ELP-HMFO-Z_E catalyzes the oxidation of HMF, and the generated hydrogen peroxide is decomposed by Z_R-CAT-ELP into H₂O and oxygen. During the oxidation of HMF, the cofactor FAD of HMFO is reduced, and molecular oxygen is needed to reoxidize the reduced FAD. The evolved oxygen from the decomposing of H₂O₂ can just meet the requirement, which can be diffused efficiently from Z_R-CAT-ELP to ELP-HMFO-Z_E due to the short distance between the two enzymes.

Fabrication of a Fibrous Metal-Organic Framework and Simultaneous Immobilization of Enzymes

A nanorod-like lanthanum metal-organic framework (LaMOF) was synthesized in aqueous solution by coordinating La(III) to the ligand 1,3,5-benzenetricarboxylic acid. The fibrous LaMOF was fabricated by splitting the nanorod-like LaMOF in a solution of d-amino acid oxidase, and the enzyme was immobilized simultaneously. Based on SEM and TEM images, STEM mapping, and spectra of XPS and FTIR, the mechanism of formation of the fibrous LaMOF and the distinct interfacial phenomena have been elucidated. The fabrication of the fibrous LaMOF and simultaneous immobilization of the enzyme were carried out in aqueous solutions at room temperature, without using any organic solvent. It is a clean and time- and energy-effective process. This work presents a distinct and clean methodology for the fabrication of the fibrous MOF. Potentially, the environmentally benign methodology can be extended to immobilize other enzymes.

Peptide Bond Formation Between the Hetrosubunits of ω-Transaminase, Alanine Dehydrogenase, and Formate Dehydrogenase Through Subunit Splicing Promoted by Heterodimerization of Leucine Zipper Motifs

For the multimeric enzymes R-ω-transaminase (RTA), alanine dehydrogenase (AlaDH), and formate dehydrogenase (FDH), peptide bond formation between the hetrosubunits has been achieved by the intein-mediated in vivo subunit splicing. The subunit ligation is triggered by the heterodimerization of an arginine rich leucine zipper motif with a glutamic acid rich leucine zipper motif. The one-by-one ligation of hetrosubunits constructs the pairing enzymes RTA&AlaDH and AlaDH&FDH. The ligation modes were analyzed based on blue native polyacrylamide gel electrophoresis (BN-PAGE). The spectra of circular dichroism (CD), fluorescence, and two-dimensional FTIR provide information on the secondary structures and stability of the pairing enzymes. The enzyme-substrate interaction was analyzed based on microscale thermophoresis analysis. In contrast to the mixed three enzymes RTA + AlaDH + FDH, the ligated enzymes RTA&AlaDH + AlaDH&FDH exhibited a much larger substrate affinity, higher stability, and significantly enhanced activity.

A mild intensity of the enzyme-support multi-point attachment promotes the optimal stabilization of mesophilic multimeric enzymes: Amine oxidase from Pisum sativum

Stabilization of dimeric enzymes requires the stabilization of the quaternary structure as well as the 3D one. Both subunits may be easily immobilized on a highly activated support. Additional stabilization of the 3D structure may be achieved via multipoint covalent attachment (MCA) on highly activated supports. In the case of monomeric enzymes or thermophilic dimeric ones, the optimal stabilization is obtained via the most intense MCA and it is associated to a small loss of catalytic activity. However, in the case of mesophilic enzymes, a very intense MCA of both subunits may promote negative effects, e.g., associated to distortions of the assembly between subunits and a subsequent very important loss of catalytic activity. A dimeric mesophilic amine oxidase from P.sativum was stabilized by MCA on glyoxyl-agarose. Both subunits were covalently immobilized on the support through the region with the highest density in Lys residues. In addition to that, an interesting activity/stabilization binomial was obtained after only 3 h of enzyme-support multiinteraction (50 % of activity/350 fold stabilization). However, after 24 h of enzyme-support multi-interaction this binomial activity-stabilization decreased down to 30/150. A moderate multiinteraction seems to be the optimal strategy for immobilization-stabilization of mesophilic dimeric enzymes and it promotes moderate losses of activity and interesting stabilizations against the combined effect of heat, acid pH and ethanol. The control of the intensity of enzyme-support multi-interactions becomes now strictly necessary.

Bioengineering oligomerization and monomerization of enzymes: learning from natural evolution to matching the demands for industrial applications

It is generally accepted that oligomeric enzymes evolve from their monomeric ancestors, and the evolution process generates superior structural benefits for functional advantages. Furthermore, adjusting the transition between different oligomeric states is an important mechanism for natural enzymes to regulate their catalytic functions for adapting environmental fluctuations in nature, which inspires researchers to mimic such a strategy to develop artificially oligomerized enzymes through protein engineering for improved performance under specific conditions. On the other hand, transforming oligomeric enzymes into their monomers is needed in fundamental research for deciphering catalytic mechanisms as well as exploring their catalytic capacities for better industrial applications. In this article, strategies for developing artificially oligomerized and monomerized enzymes are reviewed and highlighted by their applications. Furthermore, advances in the computational prediction of oligomeric structures are introduced, which would accelerate the systematic design of oligomeric and monomeric enzymes. Finally, the current challenges and future directions in this field are discussed.

A novel protein purification strategy mediated by the combination of CipA and Ssp DnaB intein

Protein purification is an indispensable step in diverse fields of biological research or production process. Conventional purification methods including the affinity purification or the usage of self-aggregating tags suffered from many drawbacks such as the complicated steps, high cost and low efficiency. Moreover, the fusion tag usually had negative effects on the activity of the target protein. To address the above issues, here we propose a novel protein purification method which needs simple operation steps, and this method is mediated by the combination of CipA protein and a mini-intein (Synechocystis sp. PCC6803 DnaB, Ssp DnaB), depending on the assembly function of CipA and the self-cleavage function of Ssp DnaB. To realize the purification, CipA-DnaB-eGFP protein was expressed and assembled into protein crystalline inclusions (PCIs) in E. coli. Then, only cell lysis, cleavage and centrifugation steps were required to purify eGFP. Purified eGFP was in the supernatant with a purity of over 90%. The cleavage efficiency and the yield of eGFP reached 51.96% and 13.99 ± 0.88 mg/L fermentation broth, respectively. Furthermore, to broaden the application of this approach, three other proteins which were maltose binding protein (MBP), ketoisovalerate decarboxylase (Kivd) and alcohol dehydrogenase (AdhP) were purified with high cleavage efficiency. The purified Kivd and AdhP remained high specific activities. This work demonstrated an effective and convenient protein purification method.

Covalent Linkage of an R-ω-Transaminase to a d-Amino Acid Oxidase through Protein Splicing to Enhance Enzymatic Catalysis of Transamination

R-ω-Transaminases (RTAs) catalyse the conversion of R-configured amines [e.g., (R)-1-phenylethylamine] into the corresponding ketones (e.g., acetophenone), by transferring an amino group from an amino donor [e.g., (R)-1-phenylethylamine] onto an amino acceptor (e.g., pyruvate), resulting in a co-product (e.g., d-alanine). d-Alanine can be deaminated back to pyruvate by d-amino acid oxidase (DAAOs). Here, through in vivo subunit splicing, the N terminus of an RTA subunit (RTA^S ) was specifically ligated to the C terminus of a DAAO subunit (DAAO^S ) through native peptide bonds (RTA&DAAO). RTA^S is in close proximity to DAAO^S , at a molecular-scale distance. Thus the transfer of pyruvate and d-alanine between RTA and DAAO can be directional and efficient. Pyruvate→d-alanine→pyruvate cycles are efficiently formed, thus promoting the forward transamination reaction. In a different, in vitro noncovalent approach, based on coiled-coil association, the RTA^S N terminus was specifically associated with the DAAO^S C terminus (RTA#DAAO). In addition, the two mixed individual enzymes (RTA+DAAO) were also studied. RTA&DAAO has a shorter distance between the paired subunits (RTA^S -DAAO^S ) than RTA#DAAO, and the number of the paired subunits is higher than in the case of RTA#DAAO, whereas RTA+DAAO cannot form the paired subunits. RTA&DAAO exhibited a transamination catalysis efficiency higher than that of RTA#DAAO and much higher than that of RTA+DAAO.

Enhancing the activity and stability of Mn-superoxide dismutase by one-by-one ligation to catalase

Dismutation of superoxide by superoxide dismutase (SOD) generates hydrogen peroxide, which may be reduced to hydroxyl radical. The generated H₂O₂ during the catalysis can have an oxidative damage to SOD. Hydrogen peroxide decomposition by catalase (CAT) can help circumvent the problem. Mn-superoxide dismutase (herein referred to as SOD) and CAT are dimeric and tetrameric proteins, respectively. Herein, through intein-mediated in vivo subunit splicing, the C-terminus of the CAT subunit (CAT^S) has been specifically ligated to the N-terminus of the SOD subunit (SOD^S) with a peptide bond. Thus, the splicing product SOD&CAT combines the superoxide anion (•O₂^-) scavenging ability and the ability of decomposing H₂O₂. The in vivo subunit splicing has little effect on the secondary structures of the enzymes as confirmed by circular dichroism (CD) spectra. Fluorescence spectra showed that the splicing product SOD&CAT has a higher stability than SOD. In the splicing product SOD&CAT, the SOD subunits are in close proximity to the CAT subunits, facilitating immediate transfer of H₂O₂ between the enzymes and enabling efficient decomposition of H₂O₂. SOD&CAT exhibited a superoxide anion (•O₂^-) scavenging ability 244% higher than that of SOD and 46% higher than that of the mixed enzymes SOD+CAT.

Protein-Engineered Biomaterials for Cancer Theranostics

Proteins are an important class of biomaterials promising a variety of applications such as drug delivery, and imaging or therapy, owing to their biodegradability, biocompatibility, as well as inherent biological activities acting as enzymes, recognizing molecules, or therapeutics by themselves. Over the few past decades, different types of proteins with desired properties have been widely explored for biomedical applications. Many therapeutic proteins have now entered clinical use. This review therefore summarizes various strategies in the engineering of biomaterials for delivery of therapeutic proteins, as well as the recent development of protein-based biomaterials for cancer theranostics.

Immobilization of enzymes using a multifunctional fusion polypeptide

OBJECTIVE

To design a fusion polypeptide combining functions of self-assembly and purification for immobilizing enzymes.

RESULTS

A collagen-like polypeptide (CLP) was fused to an elastin-like polypeptide (ELP) through genetic engineering. CLP-ELP was separately fused to superoxide dismutase (SOD) and D-amino acid oxidase (DAAO). The recombinant enzymes were purified with using reversible phase transition. The interfering effect of H₂O₂ on the secondary structures of the recombinant enzymes was significantly reduced. The stability of the recombinant enzymes against denaturing by urea was improved. SOD-CLP-ELP exhibited a proteinaceous microporous network, and DAAO-CLP-ELP exhibited micro-clusters. The superoxide anion (^•O₂^-) scavenging ability of SOD-CLP-ELP was 1.5 times that of SOD, and the catalytic efficiency of DAAO-CLP-ELP was 1.7 times that of DAAO.

CONCLUSIONS

The advantages of the CLP-ELP-fused enzymes have been demonstrated and CLP-ELP can be used to immobilize other enzymes/proteins.