High level expression of human enteropeptidase light chain in Pichia pastoris

Electrochemical Impedance Spectroscopy for the Sensing of the Kinetic Parameters of Engineered Enzymes

The study presents a promising approach to enzymatic kinetics using Electrochemical Impedance Spectroscopy (EIS) to assess fundamental parameters of modified enteropeptidases. Traditional methods for determining these parameters, while effective, often lack versatility and convenience, especially under varying environmental conditions. The use of EIS provides a novel approach that overcomes these limitations. The enteropeptidase underwent genetic modification through the introduction of single amino acid modifications to assess their effect on enzyme kinetics. However, according to the one-sample t-test results, the difference between the engineered enzymes and hEKL was not statistically significant by conventional criteria. The kinetic parameters were analyzed using fluorescence spectroscopy and EIS, which was found to be an effective tool for the real-time measurement of enzyme kinetics. The results obtained through EIS were not significantly different from those obtained through traditional fluorescence spectroscopy methods (p value >> 0.05). The study validates the use of EIS for measuring enzyme kinetics and provides insight into the effects of specific amino acid changes on enteropeptidase function. These findings have potential applications in biotechnology and biochemical research, suggesting a new method for rapidly assessing enzymatic activity.

Efficient production of fluorophore-labeled CC chemokines for biophysical studies using recombinant enterokinase and recombinant sortase

Chemokines are important immune system proteins, many of which mediate inflammation due to their function to activate and cause chemotaxis of leukocytes. An important anti-inflammatory strategy is therefore to bind and inhibit chemokines, which leads to the need for biophysical studies of chemokines as they bind various possible partners. Because a successful anti-chemokine drug should bind at low concentrations, techniques such as fluorescence anisotropy that can provide nanomolar signal detection are required. To allow fluorescence experiments to be carried out on chemokines, a method is described for the production of fluorescently labeled chemokines. First, a fusion-tagged chemokine is produced in Escherichia coli, then efficient cleavage of the N-terminal fusion partner is carried out with lab-produced enterokinase, followed by covalent modification with a fluorophore, mediated by the lab-produced sortase enzyme. This overall process reduces the need for expensive commercial enzymatic reagents. Finally, we utilize the product, vMIP-fluor, in binding studies with the chemokine binding protein vCCI, which has great potential as an anti-inflammatory therapeutic, showing a binding constant for vCCI:vMIP-fluor of 0.37 ± 0.006 nM. We also show how a single modified chemokine homolog (vMIP-fluor) can be used in competition assays with other chemokines and we report a Kd for vCCI:CCL17 of 14 μM. This work demonstrates an efficient method of production and fluorescent labeling of chemokines for study across a broad range of concentrations.

Comparison of Periplasmic and Cytoplasmic Expression of Bovine Enterokinase Light Chain in E. coli

Enterokinase enzyme is widely used in production of recombinant proteins. This enzyme is isolated from the intestine and recognizes a specific cleavage site (X↓LYS-ASP₄). Several studies have been performed to produce recombinant active enterokinase. In this study, the coding sequence of bovine enteropeptidase light chain (bEK_L) was isolated from Iranian Sarabi cattle and its expression was investigated in the periplasm and cytoplasm of E. coli by two different expression vectors, pET22 and pET32RH. RNA was extracted from the duodenum part of cattle, cDNA was amplified, the enterokinase light chain coding fragment was cloned and the expression was examined by SDS-PAGE analysis. The higher amounts of soluble enterokinase as a fusion with thioredoxin (Trx) were detected in cytoplasmic expression. The functional enterokinase was purified with a yield of 45 mg per litter by two-steps Ni²⁺ affinity chromatography. The effective activity of the enzyme implies that it can be produced in large scale for biotechnological applications.

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.

Impact of media components from different suppliers on enterokinase productivity in Pichia pastoris

Background

The aim of this study was to provide an information about the homogeneity on the level of enterokinase productivity in P. pastoris depending on different suppliers of the media components.

Results

In previous studies, we performed the optimisation process for the production of enterokinase by improving the fermentation process. Enterokinase is the ideal enzyme for removing fusion partners from target recombinant proteins. In this study, we focused our optimization efforts on the sources of cultivation media components. YPD media components were chosen as variables for these experiments. Several suppliers for particular components were combined and the optimisation procedure was performed in 24-well plates. Peptone had the highest impact on enterokinase production, where the difference between the best and worst results was threefold. The least effect on the production level was recorded for yeast extract with a 1.5 fold difference. The worst combination of media components had a activity of only 0.15 U/ml and the best combination had the activity of 0.88 U/ml, i.e., a 5.87 fold difference. A substantially higher impact on the production level of enterokinase was observed during fermentation in two selected media combinations, where the difference was almost 21-fold.

Conclusions

Results demonstrated in the present study show that the media components from different suppliers have high impact on enterokinase productivity and also provide the hypothesis that the optimization process should be multidimensional and for achieving best results it is important to perform massive process also in terms of the particular media component supplier .

Efficient expression of recombinant human telomerase inhibitor 1 (hPinX1) in Pichia pastoris

PinX1 encoded by a remarkable tumor suppressor gene and located in human chromosome 8p23 is known as telomerase inhibitor. In recent years, this protein has been of interest as clinically tumor suppressor. Pichia pastoris expression system is preferred to produce heterologous proteins and is suitable for industrial and research purposes. In the present study, human PinX1 gene (hPinX1) was cloned in E. coli One Shot TOP10 cells and overexpressed in P. pastoris strain X-33 intracellularly, using a strong AOX (alcohol oxidase) promoter. The recombinant cells were grown in shaking flask. Induction time, methanol concentration and initial pH were optimized for obtaining high levels of hPinX1 protein production. Recombinant protein production was confirmed by Western blot analysis and the relative expression levels of rhPinX1 were quantified. According to Western blot analysis, molecular mass of produced hPinX1 was determined as 47.5 kDa. At the end of optimization studies, the best fermentation conditions were determined as induction time 48 h, methanol concentration 3% and initial culture pH 5.0. This process would be an applicable way for obtaining recombinant hPinX1 using P. pastoris expression system. This is the first report on recombinant production of hPinX1 in P. pastoris.

Transcriptional engineering of the glyceraldehyde-3-phosphate dehydrogenase promoter for improved heterologous protein production in Pichia pastoris

The constitutive glyceraldehyde-3-phosphate dehydrogenase promoter (P_GAP ), which is one of the benchmark promoters of Pichia pastoris, was analyzed in terms of putative transcription factor binding sites. We constructed a synthetic library with distinct regulatory properties through deletion and duplication of these putative transcription factor binding sites and selected transcription factor (TF) genes were overexpressed or deleted to understand their roles on heterologous protein production. Using enhanced green fluorescent protein, an expression strength in a range between 0.35- and 3.10-fold of the wild-type P_GAP was obtained. Another model protein, recombinant human growth hormone was produced under control of selected promoter variants and 1.6- to 2.4-fold higher product titers were reached compared to wild-type P_GAP . In addition, a GAL4-like TF was found to be a crucial factor for the regulation of P_GAP , and its overexpression enhanced the heterologous protein production considerably (up to 2.2-fold compared to the parental strain). The synthetic P_GAP library generated enabled us to investigate the different putative transcription factors which are responsible for the regulation of P_GAP under different growth conditions, ergo recombinant protein production under P_GAP . Biotechnol. Bioeng. 2017;114: 2319-2327. © 2017 Wiley Periodicals, Inc.

Optimization of the fermentation and downstream processes for human enterokinase production in Pichia pastoris

Enterokinase is one of the most frequently used enzymes for the removal of affinity tags from target recombinant proteins. In this study, several fermentation strategies were assayed for the production of human enterokinase in Pichia pastoris under constitutive GAP promoter. Two of them with controlled specific growth rate during whole cultivation showed a very low enterokinase activity, under 1 U/ml, of the fermentation medium. On the contrary, the combined fermentation with a maximum specific growth rate at the initial phase of the fermentation and stationary-like phase during the rest of the fermentation showed a significant accumulation of the enterokinase in the medium, which counted up to 1400 U/ml. Lower cultivation temperature had a negative impact on the enzyme accumulation during this fermentation strategy. Downstream processes were focused on buffer environment optimization directly after cultivation, as at this time, the most amount of the activity is eliminated by endogenous proteases. Slightly positive effect on enzyme activity in the medium had an addition of liquid storage solution of EDTA and KOH to adjust pH to 8 and molarity of the EDTA to 50 mM. During the purification process, a significant amount of the enzyme was detected to be lost, which counted up to 90%. The purified enzyme, enterokinase, kept quality standard of the published enzymes.

Improving the secretion of a methyl parathion hydrolase in Pichia pastoris by modifying its N-terminal sequence

Pichia pastoris is commonly used to express and secrete target proteins, although not all recombinant proteins can be successfully produced. In this study, we used methyl parathion hydrolase (MPH) from Ochrobactrum sp. M231 as a model to study the importance of the N-terminus of the protein for its secretion. While MPH can be efficiently expressed intracellularly in P. pastoris, it is not secreted into the extracellular environment. Three MPH mutants (N₆₆-MPH, D₁₀-MPH, and N₉-MPH) were constructed through modification of its N-terminus, and the secretion of each by P. pastoris was improved when compared to wild-type MPH. The level of secreted D₁₀-MPH was increased to 0.21 U/mL, while that of N₉-MPH was enhanced to 0.16 U/mL. Although N₆₆-MPH was not enzymatically active, it was secreted efficiently, and was identified by SDS-PAGE. These results demonstrate that the secretion of heterologous proteins in P. pastoris may be improved by modifying their N-terminal structures.

Heterogeneous catalysis on the phage surface: Display of active human enteropeptidase

Enteropeptidase (EC 3.4.21.9) plays a key role in mammalian digestion as the enzyme that physiologically activates trypsinogen by highly specific cleavage of the trypsinogen activation peptide following the recognition sequence D4K. The high specificity of enteropeptidase makes it a powerful tool in modern biotechnology. Here we describe the application of phage display technology to express active human enteropeptidase catalytic subunits (L-HEP) on M13 filamentous bacteriophage. The L-HEP/C122S gene was cloned in the g3p-based phagemid vector pHEN2m upstream of the sequence encoding the phage g3p protein and downstream of the signal peptide-encoding sequence. Heterogeneous catalysis of the synthetic peptide substrate (GDDDDK-β-naphthylamide) cleavage by phage-bound L-HEP was shown to have kinetic parameters similar to those of soluble enzyme, with the respective Km values of 19 μM and 20 μM and kcat of 115 and 92 s(-1). Fusion proteins containing a D4K cleavage site were cleaved with phage-bound L-HEP/C122S as well as by soluble L-HEP/C122S, and proteolysis was inhibited by soybean trypsin inhibitor. Rapid large-scale phage production, one-step purification of phage-bound L-HEP, and easy removal of enzyme activity from reaction samples by PEG precipitation make our approach suitable for the efficient removal of various tag sequences fused to the target proteins. The functional phage display technology developed in this study can be instrumental in constructing libraries of mutants to analyze the effect of structural changes on the activity and specificity of the enzyme or generate its desired variants for biotechnological applications.

Human enteropeptidase light chain: bioengineering of recombinants and kinetic investigations of structure and function

The serine protease enteropeptidase exhibits a high level of substrate specificity for the cleavage sequence DDDDK∼ X, making this enzyme a useful tool for the separation of recombinant protein fusion domains. In an effort to improve the utility of enteropeptidase for processing fusion proteins and to better understand its structure and function, two substitution variants of human enteropeptidase, designated R96Q and Y174R, were created and produced as active (>92%) enzymes secreted by Pichia pastoris with yields in excess of 1.7 mg/Liter. The Y174R variant showed improved specificities for substrates containing the sequences DDDDK (kcat /KM = 6.83 × 10⁶ M⁻¹ sec⁻¹) and DDDDR (kcat /KM = 1.89 × 10⁷ M⁻¹ sec⁻¹) relative to all other enteropeptidase variants reported to date. BPTI inhibition of Y174R was significantly decreased. Kinetic data demonstrate the important contribution of the positively charged residue 96 to extended substrate specificity in human enteropeptidase. Modeling shows the importance of the charge-charge interactions in the extended substrate binding pocket.