L-asparaginase from Erwinia carotovora. An improved recovery and purification process using affinity chromatography

Recent advances in biotechnology for marine enzymes and molecules

The marine environment is the most biologically and chemically diverse habitat on Earth, and provides numerous marine-derived products, including enzymes and molecules, for industrial and pharmaceutical applications. Marine biotechnology provides important biological resources from marine habitat conservation to applied science. In recent years, advances in techniques in interdisciplinary research fields, including metabolic engineering and synthetic biology have significantly improved the production of marine-derived commodities. In this review, we outline the recent progress in the use or marine enzymes and molecules in biotechnology, including newly discovered products, function optimization of enzymes, and production improvement of small molecules.

Quality Control and Downstream Processing of Therapeutic Enzymes

Therapeutic enzymes are a commercially minor but clinically important area of biopharmaceuticals. An array of therapeutic enzymes has been developed for a variety of human diseases, including leukaemia and enzyme-deficiency diseases such as Gaucher's disease. Production and testing of therapeutic enzymes is strictly governed by regulatory bodies in each country around the world, and batch-to-batch consistency is crucially important. Manufacture of a batch starts with the fermentation or cell culture stage. After expression of the therapeutic enzyme in a cell culture bioreactor, robust and reproducible protein purification, or downstream processing (DSP) of the target product, is critical to ensuring safe delivery of these medicines. Modern processing technology, including the use of disposable processing equipment, has greatly improved the DSP development pathway in terms of robustness and speed to clinic. Once purified, the drug substance undergoes rigorous quality control (QC) testing according to current regulatory guidance, to enable release to the clinic and patient. QC testing is conducted to ensure the safety, purity, identity, potency and strength of the medicinal product, requiring multiple analytical methods that are rigorously validated and monitored for robust performance. Several case studies, including L-asparaginase and asfotase alfa, are discussed to illustrate the methods described herein.

Molecular Cloning, Biochemical Characterization, and Antitumor Properties of a Novel L-Asparaginase from Synechococcus elongatus PCC6803

L-asparaginase (EC 3.5.1.1), which catalyzes the deamidation of L-asparagine to L-aspartic acid and ammonia, has been widely used as a key therapeutic tool in the treatment of tumors. The current commercially available L-asparaginases, produced from bacteria, have signs of toxicity and hypersensitivity reactions during the course of tumor therapy. Therefore, searching for L-asparaginases with unique biochemical properties and fewer adverse effects was the objective of this work. In this study, cyanobacterial strain Synechococcus elongatus PCC6803 was found as a novel source of L-asparaginase. The L-asparaginase gene coding sequence (gi:939195038) was cloned and expressed in E. coli BL21(DE3), and the recombinant protein (Se.ASPII) was purified by affinity chromatography. The enzyme has high affinity towards L-asparagine and shows very weak affinity towards L-glutamine. The enzymatic properties of the recombinant enzyme were investigated, and the kinetic parameters (K_m, V_max) were measured. The pH and temperature dependence profiles of the novel enzyme were analyzed. The work was extended to measure the antitumor properties of the novel enzyme against different human tumor cell lines.

Recombinant L-Asparaginase from Zymomonas mobilis: A Potential New Antileukemic Agent Produced in Escherichia coli

L-asparaginase is an enzyme used as a chemotherapeutic agent, mainly for treating acute lymphoblastic leukemia. In this study, the gene of L-asparaginase from Zymomonas mobilis was cloned in pET vectors, fused to a histidine tag, and had its codons optimized. The L-asparaginase was expressed extracellularly and intracellularly (cytoplasmically) in Escherichia coli in far larger quantities than obtained from the microorganism of origin, and sufficient for initial cytotoxicity tests on leukemic cells. The in silico analysis of the protein from Z. mobilis indicated the presence of a signal peptide in the sequence, as well as high identity to other sequences of L-asparaginases with antileukemic activity. The protein was expressed in a bioreactor with a complex culture medium, yielding 0.13 IU/mL extracellular L-asparaginase and 3.6 IU/mL intracellular L-asparaginase after 4 h of induction with IPTG. The cytotoxicity results suggest that recombinant L-asparaginase from Z. mobilis expressed extracellularly in E.coli has a cytotoxic and cytostatic effect on leukemic cells.

Cloning, expression and characterization of L-asparaginase from Pseudomonas fluorescens for large scale production in E. coli BL21

l-Asparaginase (E.C. 3.5.1.1) is used as an anti-neoplastic drug in the treatment of acute lymphoblastic leukemia. l-Asparaginase from Pseudomonas fluorescens was cloned and overexpressed in E. coli BL21. The Enzyme was found to be a Fusion protein-asparaginase complex which was given a lysozyme treatment and sonication, and then was purified in a Sepharose 6B column. The enzymatic properties of the recombinant enzyme were studied and the kinetic parameters were determined with kilometre of 109.99 mM and V_max of 2.88 µM/min. Recombinant enzyme showed pH optima at 6.3 and temperature optima at 34 °C. Asp gene was successfully cloned into E. coli BL21 which produced high level of asparaginase intracellularly with 85.25 % recovery of enzyme with a specific activity of 0.94 IU/mg protein. The enzyme was a tetramer with molecular weight of approximately 141 kDa.

[Bacterial recombinant L-asparaginases: properties, structure and anti-proliferative activity]

For more than 40 years L-asparaginases are used in combined therapy of acute lymphoblastic leukemia in children and the range of tumors sensitive to these enzymes constantly extends. This review summarizes results of studies aimed at creation of new systems for heterological expression of bacterial L-asparaginases as Erwinia carotovora (EwA), Helicobacter pylori (HpA), Yersinia pseudotuberculosis (YpA) and Rhodospirillum rubrum (RrA); special attention is paid to isolation of purified enzymes and their crystallization, modification by chitosan/polyethylene, physicochemical, kinetic and structural properties characterization, and the study of the cytotoxic or anti-proliferative activity of new recombinant L-asparaginases on cell cultures in vitro. The resultant recombinant L-asparaginases (EwA, YpA, HpA и RrA) exhibit reasonable cytotoxic action on the human leukemia cells comparable to the pharmacologically available L-asparaginase EcA and represent practical interest in respect to creation, on their basis, new effective antineoplastic remedies. Further prospects of researches on bacterial L-asparaginases are associated with development of analogs of Rhodospirillum rubrum L-asparaginase (RrA) by means of directed changes of the protein structure using genetic engineering, development of chito-PEGylation for receiving L-asparaginase preparations with improved pharmacokinetic characteristics.

Cloning, expression, purification and characterisation of Erwinia carotovora L-asparaginase in Escherichia coli

Background:

For the past 30 years, bacterial L-asparaginases have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukemia. It is found in a variety of organisms such as microbes, plants and mammals. Their intrinsic low-rate glutaminase activity, however, causes serious side-effects, including neurotoxicity, hepatitis, coagulopathy and other dysfunctions. Erwinia carotovora asparaginase shows decreased glutaminase activity, so it is believed to have fewer side-effects in leukemia therapy. Our aim was to clone, express, purify and characterize E. carotovora asparaginase.

Materials and Methods:

L-asparaginase from E. carotovora NCYC 1526 (ErA) was cloned and expressed in Escherichia coli strain BL21 (DE3). The enzyme was purified to homogeneity by affinity chromatography. Various conditions were tested to maximize the production of recombinant asparaginase in E. coli.

Results:

A new L. asparaginase from E. carotovora NCYC 1526 (ErA) was successfully cloned, expressed and purified in E. coli BL21 (DE3). The specific activity of the enzyme was 430 IU/mg.

Conclusion:

The results of the present work form the basis for a new engineered form of ErA for future therapeutic use, which could be extended with crystallographic studies.

TK1656, a thermostable l-asparaginase from Thermococcus kodakaraensis, exhibiting highest ever reported enzyme activity

Two L-asparaginase homologs, TK1656 and TK2246, have been found in the genome of Thermococcus kodakaraensis. The gene encoding TK1656 consists of 984 nucleotides corresponding to a polypeptide of 328 amino acids. To examine the properties of TK1656, the structural gene was cloned, expressed in Escherichia coli and the purified gene product was characterized. TK1656 exhibited high asparaginase activity (2350 U mg⁻¹) but no glutaminase activity. The enzyme also displayed the D-asparaginase activity but 50% to that of L-asparaginase. The highest activity was observed at 85°C and pH 9.5. TK1656 catalyzed the conversion of L-asparagine to L-aspartatic acid and ammonia following Michaelise-Menten kinetics with a K(m) and V(max) values of 5.5 mM and 3300 mmol min⁻¹ mg⁻¹, respectively. The activation energy from the linear Arrhenius plot was found to be 58 kJ mol⁻¹. Unfolding studies suggested that urea could not induce complete unfolding and inactivation of TK1656 even at a concentration 8 M; however, in the presence of 4 M guanidine hydrochloride enzyme structure was unfolded with complete loss of enzyme activity.

Cloning, expression and characterization of l-asparaginase from Withania somnifera L. for large scale production

l-Asparaginase (E.C. 3.5.1.1) is used as a therapeutic agent in the treatment of acute childhood lymphoblastic leukemia. It is found in a variety of organisms such as microbes, plants and mammals. In plants, l-asparaginase enzymes are required to catalyze the release of ammonia from asparagine, which is the main nitrogen-relocation molecule in these organisms. An Indian medicinal plant, Withania somnifera was reported as a novel source of l-asparaginase. l-Asparaginase from W. somnifera was cloned and overexpressed in E. coli. The enzymatic properties of the recombinant enzyme were investigated and the kinetic parameters (K(m), k(cat)) for a number of substrates were determined. The kinetic parameters of selected substrates were determined at various pH and the pH- and temperature-dependence profiles were analyzed. WA gene successfully cloned into E. coli BL21 (DE3) showed high asparaginase activity with a specific activity of 17.3 IU/mg protein.

Purification, Characterization, and Effect of Thiol Compounds on Activity of the Erwinia carotovora L-Asparaginase

L-asparaginase was extracted from Erwinia carotovora and purified by ammonium sulfate fractionation (60–70%), Sephadex G-100, CM cellulose, and DEAE sephadex chromatography. The apparent Mr of enzyme under nondenaturing and denaturing conditions was 150 kDa and 37 ± 0.5 kDa, respectively. L-asparaginase activity was studied in presence of thiols, namely, L-cystine (Cys), L-methionine (Met), N-acetyl cysteine (NAC), and reduced glutathione (GSH). Kinetic parameters in presence of thiols (10–400 μM) showed an increase in V_max values (2000, 2223, 2380, 2500, and control 1666.7 μmoles mg⁻¹min⁻¹) and a decrease in K_m values (0.086, 0.076, 0.062, 0.055 and control 0.098 mM) indicating nonessential mode of activation. K_A values displayed propensity to bind thiols. A decrease in V_max/K_m ratio in concentration plots showed inverse relationship between free thiol groups (NAC and GSH) and bound thiol group (Cys and Met). Enzyme activity was enhanced in presence of thiol protecting reagents like dithiothreitol (DTT), 2-mercaptoethanol (2-ME), and GSH, but inhibited by p-chloromercurybenzoate (PCMB) and iodoacetamide (IA).

Tailoring structure-function properties of L-asparaginase: engineering resistance to trypsin cleavage

Bacterial L-ASNases (L-asparaginases) catalyse the conversion of L-asparagine into L-aspartate and ammonia, and are widely used for the treatment of ALL (acute lymphoblastic leukaemia). In the present paper, we describe an efficient approach, based on protein chemistry and protein engineering studies, for the construction of trypsin-resistant PEGylated L-ASNase from Erwinia carotovora (EcaL-ASNase). Limited proteolysis of EcaL-ASNase with trypsin was found to be associated with a first cleavage of the peptide bond between Lys53 and Gly54, and then a second cleavage at Arg206-Ser207 of the C-terminal fragment, peptide 54-327, showing that the initial recognition sites for trypsin are Lys53 and Arg206. Site-directed mutagenesis of Arg206 to histidine followed by covalent coupling of mPEG-SNHS [methoxypoly(ethylene glycol) succinate N-hydroxysuccinimide ester] to the mutant enzyme resulted in an improved modified form of EcaL-ASNase that retains 82% of the original catalytic activity, exhibits enhanced resistance to trypsin degradation, and has higher thermal stability compared with the wild-type enzyme.

Cloning, expression and characterisation of Erwinia carotovora l-asparaginase

Bacterial L-asparaginases (E.C. 3.5.1.1) have been used as therapeutic agents in the treatment of acute childhood lymphoblastic leukaemia. L-asparaginase from Erwinia carotovora NCYC 1526 (ErA) was cloned and expressed in E. coli. The enzyme was purified to homogeneity by a two-step procedure comprising cation-exchange chromatography and affinity chromatography on immobilised L-asparagine. The enzymatic properties of the recombinant enzyme were investigated and the kinetic parameters (K(m), k(cat)) for a number of substrates were determined. Molecular modelling studies were also employed to create a model of ErA, based on the known structure of the Erwinia chrysanthemi enzyme. The molecular model was used to help interpret biochemical data concerning substrate specificity and catalytic mechanism of the enzyme. The kinetic parameters of selected substrates were determined at various pH values, and the pH-dependence profiles of V(max) and V(max)/K(m) were analyzed. The pH-dependence of V(max) shows one transition in the acidic pH range with pK(a)=5.4, and the pH-dependence of V(max)/K(m) exhibits two transitions with pK(a)=5.4 and 8.5. Based on analysis of alternative substrates and molecular modelling studies, it was concluded that the pK(a) at the acidic pH range corresponds to the active site residues Asp115 or Glu82, whereas the pK(a) observed at the alkaline pH range is not due to substrate amino group ionisation, but rather is the result of enzyme ionisation. The effect of temperature and viscosity on the catalytic activity of the enzyme was also investigated and it was concluded that the rate-limiting step of the catalytic reaction is relevant to structural transitions of the protein. Thermodynamic analysis of the activity data showed that the activation energies are dependent on the substrate, and entropy changes appear to be the main determinant contributing to substrate specificity.

Solid-phase enzyme modification via affinity chromatography

In the present study antileukemic enzyme L-asparaginase (ASNase) and catalase (as a model enzyme) were modified in solid-phase with activated polyethylene glycol (PEG(2)) by using ligand-immobilized affinity column systems L-asparagine-Sepharose CL-4B and Procion red-Sepharose CL-4B, respectively. Studies on change of specific activity with modification time showed negligible differences between batches of modified catalase. Modification of ASNase for 1 h resulted in 50.2% recovery of the specific activity and the attachment of 69 molecules of PEG(2) per molecule of ASNase forming 'PEGylated ASNase'. Sequential modification of ASNase by activated PEG and heparin resulted in coupling of about nine molecules of heparin per molecule of PEGylated ASNase. Intravenous (i.v.) administration of PEG(2)-modified ASNase showed prolonged presence in the blood circulation and no adverse effects or symptoms of anaphylaxis were observed in presensitized mice.

Affinity chromatography for protein isolation

Thousands of reports concerning protein purification have appeared in the past year, and over 150 of these involved, at least in part, the affinity chromatography process. Immobilized membrane affinity chromatography, temperature-programmed elution, and centrifugal affinity chromatography are among the most significant new techniques amid the myriads of applications in this mature field.