Enterokinase monolithic bioreactor as an efficient tool for biopharmaceuticals preparation: on-line cleavage of fusion proteins and analytical characterization of released products

Preparation of recombinant neuritin protein

Neuritin plays an important role in promoting nerve injury repair and maintaining synaptic plasticity, making it a potential therapeutic target for the treatment of nerve injury and neurodegenerative diseases. The present study aimed to obtain an active, unlabeled neuritin protein. Initially, a neuritin protein expression system with an enterokinase site was constructed in Escherichia coli. After optimizing induction conditions and screening for high expression, a neuritin recombinant protein with purity exceeding 85% was obtained through Ni-affinity chromatography. Subsequently, unlabeled neuritin with a molecular weight of 11 kDa was obtained through the enzymatic cleavage of the His label using an enterokinase. Furthermore, a neuritin recombinant protein with purity exceeding 95% was obtained using gel chromatography. Functional investigations revealed that neurite outgrowth of PC12 cells was stimulated by the isolated neuritin. This study establishes a method to obtain active and unlabeled neuritin protein, providing a foundation for subsequent research on its biological functions.

Recombinant Production of Bovine Enteropeptidase Light Chain in SHuffle® T7 Express and Optimization of Induction Parameters

Enteropeptidase is a duodenum serine protease that triggers the activation of pancreatic enzymes by remarkably specific cleavages after lysine residues of peptidyl substrate (Asp)₄-Lys. This high specific cleavage makes the enzyme a widely used biotechnological tool in laboratory researches and industrial scale. Previous studies both in small and large scales were showed low expression and miss-folding of the expressed protein. In this study, the DNA sequence encoding the light chain (catalytic subunit) of bovine enteropeptidase (EP_L) was subcloned into plasmid pET-32b, downstream to the DNA encoding the fusion partner thioredoxin immediately after the EP_L cleavage site. SHuffle® T7 Express was selected as an expression host due to the ability to promote proper folding and correction of the mis-oxidized bonds. Expression and purification of protein was performed, and the result of biological activity confirmed that the active EP_L was obtained. Optimization of protein expression conditions was accomplished by response surface methodology for significant factors including induction temperature, duration of induction, inducer concentration and OD₆₀₀ of induction. The best conditions were achieved in 1.05 mM IPTG at OD₆₀₀ of 0.6 for seven h incubation at 26.5 °C, and a high level of protein expression was obtained in the optimized condition.

Affinity monolith chromatography: A review of general principles and recent developments

Affinity monolith chromatography (AMC) is a liquid chromatographic technique that utilizes a monolithic support with a biological ligand or related binding agent to isolate, enrich, or detect a target analyte in a complex matrix. The target-specific interaction exhibited by the binding agents makes AMC attractive for the separation or detection of a wide range of compounds. This article will review the basic principles of AMC and recent developments in this field. The supports used in AMC will be discussed, including organic, inorganic, hybrid, carbohydrate, and cryogel monoliths. Schemes for attaching binding agents to these monoliths will be examined as well, such as covalent immobilization, biospecific adsorption, entrapment, molecular imprinting, and coordination methods. An overview will then be given of binding agents that have recently been used in AMC, along with their applications. These applications will include bioaffinity chromatography, immunoaffinity chromatography, immobilized metal-ion affinity chromatography, and dye-ligand or biomimetic affinity chromatography. The use of AMC in chiral separations and biointeraction studies will also be discussed.

Expression and purification of soluble and active human enterokinase light chain in Escherichia coli

•

Recombinant production of soluble, active enterokinase (EK) is challenging.

•

Maltose binding protein-fusion improves EK solubility but reduces activity.

•

GroEL/ES and Erv2/PDI induces correct refolding and improves EK activity.

•

Replacing free cysteine with serine dramatically improves EK activity.

Human enterokinase light chain (hEK_L) specifically cleaves the sequence (Asp)₄-Lys↓X (D₄K), making this a frequently used enzyme for site-specific cleavage of recombinant fusion proteins. However, hEK_L production from Escherichia coli is limited due to intramolecular disulphide bonds. Here, we present strategies to obtain soluble and active hEK_L from E. coli by expressing the hEK_L variant C112S fused with maltose-binding protein (MBP) through D₄K and molecular chaperons including GroEL/ES. The fusion protein self-cleaved in vivo, thereby removing the MBP in the E. coli cells. Thus, the self-cleaved hEK_L variant was released into the culture medium. One-step purification using HisTrap™ chromatography purified the hEK_L variant exhibiting an enzymatic activity of 3.1 × 10³ U/mL (9.934 × 10⁵ U/mg). The approaches presented here greatly simplify the purification of hEK_L from E. coli without requiring refolding processes.

Immobilized enzyme reactors based on nucleoside phosphorylases and 2'-deoxyribosyltransferase for the in-flow synthesis of pharmaceutically relevant nucleoside analogues

In this work, a mono- and a bi-enzymatic analytical immobilized enzyme reactors (IMERs) were developed as prototypes for biosynthetic purposes and their performances in the in-flow synthesis of nucleoside analogues of pharmaceutical interest were evaluated. Two biocatalytic routes based on nucleoside 2'-deoxyribosyltransferase from Lactobacillus reuteri (LrNDT) and uridine phosphorylase from Clostridium perfrigens (CpUP)/purine nucleoside phosphorylase from Aeromonas hydrophila (AhPNP) were investigated in the synthesis of 2'-deoxy, 2',3'-dideoxy and arabinonucleoside derivatives. LrNDT-IMER catalyzed the synthesis of 5-fluoro-2'-deoxyuridine and 5-iodo-2'-deoxyuridine in 65-59% conversion yield, while CpUP/AhPNP-IMER provided the best results for the preparation of arabinosyladenine (60% conversion yield). Both IMERs proved to be promising alternatives to chemical routes for the synthesis of nucleoside analogues. The developed in-flow system represents a powerful tool for the fast production on analytical scale of nucleosides for preliminary biological tests.

Development of an integrated chromatographic system for ω-transaminase-IMER characterization useful for flow-chemistry applications

An integrated chromatographic system was developed to rapidly investigate the biocatalytic properties of ω-transaminases useful for the synthesis of chiral amines. ATA-117, an (R)-selective ω-transaminase was selected as a proof of concept. The enzyme was purified and covalently immobilized on an epoxy monolithic silica support to create an immobilized enzyme reactor (IMER). Reactor efficiency was evaluated in the conversion of a model substrate. The IMER was coupled through a switching valve to an achiral analytical column for separation and quantitation of the transamination products. The best conditions of the transaminase-catalyzed bioconversion were optimized by a design of experiments (DoE) approach. The production of (R)-1-(4-methoxyphenyl)propan-2-amine and (R)-1-methyl-3-phenylpropylamine, intermediates for the synthesis of the bronchodilator formoterol and the antihypertensive dilevalol respectively, was achieved in the presence of different amino donors. The enantiomeric excess (ee) was determined off-line by developing a derivatization procedure using Nα-(2,4-dinitro-5-fluorophenyl)-L-alaninamide reagent. The most satisfactory conversion yields were 60% for (R)-1-(4-methoxyphenyl)propan-2-amine and 29% for (R)-1-methyl-3-phenylpropylamine, using isopropylamine as amino donor. The enantiomeric excess of the reactions were 84%_R and 99%_R, respectively.

Site-specific, covalent immobilization of an engineered enterokinase onto magnetic nanoparticles through transglutaminase-catalyzed bioconjugation

Enterokinase (EK) is one of the most popular enzymes for the in vitro cleavage of fusion proteins due to its high degree of specificity for the amino-acid sequence (Asp)₄-Lys. Enzyme reusability is desirable for reducing operating costs and facilitating the industrial application of EK. In this work, we report the controlled, site-specific and covalent cross-linking of an engineered EK_LC on amine-modified magnetic nanoparticles (NH₂-MNPs) via microbial transglutaminase-catalyzed bioconjugation for the development of the oriented-immobilized enzyme, namely, EK_LC@NH₂-MNP biocatalyst. Upon the site-specific immobilization, approximately 90% EK_LC enzymatic activity was retained, and the biocatalyst exhibited more than 85% of initial enzymatic activity regardless of storage or reusable stability over a month. The EK_LC@NH₂-MNP biocatalyst was further applied to remove the His tag-(Asp)₄-Lys fusion partner from the His tag-(Asp)₄-Lys-(GLP-1)₃ substrate fusion protein, result suggested the EK_LC@NH₂-MNP possessed remarkable reusability, without a significant decrease of enzymatic activity over 10 cycles (P >  0.05). Supported by the unique properties of MNPs, the proposed EK_LC@NH₂-MNP biocatalyst is expected to promote the economical utilization of enterokinase in fusion protein cleavage.