l-Asparaginase as Potent Anti-leukemic Agent and Its Significance of Having Reduced Glutaminase Side Activity for Better treatment of Acute Lymphoblastic Leukaemia

Asparagine: A key metabolic junction in targeted tumor therapy

Nutrient bioavailability in the tumor microenvironment plays a pivotal role in tumor proliferation and metastasis. Among these nutrients, glutamine is a key substance that promotes tumor growth and proliferation, and its downstream metabolite asparagine is also crucial in tumors. Studies have shown that when glutamine is exhausted, tumor cells can rely on asparagine to sustain their growth. Given the reliance of tumor cell proliferation on asparagine, restricting its bioavailability has emerged as promising strategy in cancer treatment. For instance, the use of asparaginase, an enzyme that depletes asparagine, has been one of the key chemotherapies for acute lymphoblastic leukemia (ALL). However, tumor cells can adapt to asparagine restriction, leading to reduced chemotherapy efficacy, and the mechanisms by which different genetically altered tumors are sensitized or adapted to asparagine restriction vary. We review the sources of asparagine and explore how limiting its bioavailability impacts the progression of specific genetically altered tumors. It is hoped that by targeting the signaling pathways involved in tumor adaptation to asparagine restriction and certain factors within these pathways, the issue of drug resistance can be addressed. Importantly, these strategies offer precise therapeutic approaches for genetically altered cancers.

Preclinical evaluation of engineered L-asparaginase variants to improve the treatment of Acute Lymphoblastic Leukemia

INTRODUCTION

Escherichia coli l-asparaginase (EcA), an integral part of multi-agent chemotherapy protocols of acute lymphoblastic leukemia (ALL), is constrained by safety concerns and the development of anti-asparaginase antibodies. Novel variants with better pharmacological properties are desirable.

METHODS

Thousands of novel EcA variants were constructed using protein engineering approach. After preliminary screening, two mutants, KHY-17 and KHYW-17 were selected for further development. The variants were characterized for asparaginase activity, glutaminase activity, cytotoxicity and antigenicity in vitro. Immunogenicity, pharmacokinetics, safety and efficacy were tested in vivo. Binding of the variants to pre-existing antibodies in primary and relapsed ALL patients' samples was evaluated.

RESULTS

Both variants showed similar asparaginase activity but approximately 24-fold reduced glutaminase activity compared to wild-type EcA (WT). Cytotoxicity against Reh cells was significantly higher with the mutants, although not toxic to human PBMCs than WT. The mutants showed approximately 3-fold lower IgG and IgM production compared to WT. Pharmacokinetic study in BALB/c mice showed longer half-life of the mutants (KHY-17- 267.28±9.74; KHYW-17- 167.41±14.4) compared to WT (103.24±18). Single and repeat-doses showed no toxicity up to 2000 IU/kg and 1600 IU/kg respectively. Efficacy in ALL xenograft mouse model showed 80-90 % reduction of leukemic cells with mutants compared to 40 % with WT. Consequently, survival was 90 % in each mutant group compared to 10 % with WT. KHYW-17 showed over 2-fold lower binding to pre-existing anti-asparaginase antibodies from ALL patients treated with l-asparaginase.

CONCLUSION

EcA variants demonstrated better pharmacological properties compared to WT that makes them good candidates for further development.

Rational engineering and insight for a L-glutaminase activity reduced type II L-asparaginase from Bacillus licheniformis and its antileukemic activity in vitro

Type II L-asparaginase (ASNase) has been approved by the FDA for treating acute lymphoid leukemia (ALL), but its therapeutic effect is limited by low catalytic efficiency and L-glutaminase (L-Gln) activity. This study utilized free energy based molecular dynamics calculations to identify residues associated with substrate binding in Bacillus licheniformis L-asparaginase II (BLASNase) with high catalytical activity. After saturation and combination mutagenesis, the mutant LGT (74 L/75G/111 T) with intensively reduced l-glutamine catalytic activity was generated. The l-glutamine/L-asparagine activity (L-Gln/L-Asn) of LGT was only 6.6 % of parent BLASNase, whereas the L-asparagine (L-Asn) activity was preserved >90 %. Furthermore, structural comparison and molecular dynamics calculations indicated that the mutant LGT had reduced binding ability and affinity towards l-glutamine. To evaluate its effect on acute leukemic cells, LGT was supplied in treating MOLT-4 cells. The experimental results demonstrated that LGT was more cytotoxic and promoted apoptosis compared with commercial Escherichia coli ASNase. Overall, our findings firstly provide insights into reducing l-glutamine activity without impacting L-asparagine activity for BLASNase to possess remarkable potential for anti-leukemia therapy.

L-Asparaginase as the gold standard in the treatment of acute lymphoblastic leukemia: a comprehensive review

L-Asparaginase is an antileukemic drug long approved for clinical use to treat childhood acute lymphoblastic leukemia, the most common cancer in this population worldwide. However, the efficacy and its use as a drug have been subject to debate due to the variety of adverse effects that patients treated with it present, as well as the prompt elimination in plasma, the need for multiple administrations, and high rates of allergic reactions. For this reason, the search for new, less immunogenic variants has long been the subject of study. This review presents the main aspects of the L-asparaginase enzyme from a structural, pharmacological, and clinical point of view, from the perspective of its use in chemotherapy protocols in conjunction with other drugs in the different treatment phases.

Appraisal of cytotoxicity and acrylamide mitigation potential of L-asparaginase SlpA from fish gut microbiome

L-asparaginase catalyzes the hydrolysis of L-asparagine to L-aspartic acid and ammonia. It has application in the treatment of acute lymphoblastic leukemia in children, as well as in other malignancies, in addition to its role as a food processing aid for the mitigation of acrylamide formation in the baking industry. Its use in cancer chemotherapy is limited due to problems such as its intrinsic glutaminase activity and associated side effects, leading to an increased interest in the search for novel L-asparaginases without L-glutaminase activity. This study reports the cloning and expression of an L-asparaginase contig obtained from whole metagenome shotgun sequencing of Sardinella longiceps gut microbiota. Purified recombinant glutaminase-free L-asparaginase SlpA was a 74 kDa homodimer, with maximal activity at pH 8 and 30 °C. K_m and V_max of SlpA were determined to be 3.008 mM and 0.014 mM/min, respectively. SlpA displayed cytotoxic activity against K-562 (chronic myeloid leukemia) and MCF-7 (breast cancer) cell lines with IC₅₀ values of 0.3443 and 2.692 U/mL, respectively. SlpA did not show any cytotoxic activity against normal lymphocytes and was proved to be hemocompatible. Pre-treatment of biscuit and bread dough with different concentrations of SlpA resulted in a clear, dose-dependent reduction of acrylamide formation during baking. KEY POINTS: • Cloned and expressed L-asparaginase (SlpA) from fish gut microbiota • Purified SlpA displayed good cytotoxicity against K-562 and MCF-7 cell lines • SlpA addition caused a significant reduction of acrylamide formation during baking.

Novel Insights on the Use of L-Asparaginase as an Efficient and Safe Anti-Cancer Therapy

Simple Summary

L-asparaginase (L-ASNase) therapy is key for achieving the very high cure rate of pediatric acute lymphoblastic leukemia (ALL), yet its use is mostly confined to this indication. One main reason preventing the expansion of today’s FDA-approved L-ASNases to solid cancers is their high toxicity and side effects, which become especially challenging in adult patients. The design of optimized L-ASNase molecules provides opportunities to overcome these unwanted toxicities. An additional challenge to broader application of L-ASNases is how cells can counter the pharmacological effect of this drug and the identification of L-ASNases resistance mechanisms. In this review, we discuss recent insights into L-ASNase adverse effects, resistance mechanisms, and how novel L-ASNase variants and drug combinations can expand its clinical applicability, with a focus on both hematological and solid tumors.

Abstract

L-Asparaginase (L-ASNase) is an enzyme that hydrolyses the amino acid asparagine into aspartic acid and ammonia. Systemic administration of bacterial L-ASNase is successfully used to lower the bioavailability of this non-essential amino acid and to eradicate rapidly proliferating cancer cells with a high demand for exogenous asparagine. Currently, it is a cornerstone drug in the treatment of the most common pediatric cancer, acute lymphoblastic leukemia (ALL). Since these lymphoblasts lack the expression of asparagine synthetase (ASNS), these cells depend on the uptake of extracellular asparagine for survival. Interestingly, recent reports have illustrated that L-ASNase may also have clinical potential for the treatment of other aggressive subtypes of hematological or solid cancers. However, immunogenic and other severe adverse side effects limit optimal clinical use and often lead to treatment discontinuation. The design of optimized and novel L-ASNase formulations provides opportunities to overcome these limitations. In addition, identification of multiple L-ASNase resistance mechanisms, including ASNS promoter reactivation and desensitization, has fueled research into promising novel drug combinations to overcome chemoresistance. In this review, we discuss recent insights into L-ASNase adverse effects, resistance both in hematological and solid tumors, and how novel L-ASNase variants and drug combinations can expand its clinical applicability.

Rhizopus oryzae AM16; a new hyperactive L‑asparaginase producer: Semi solid‑state production and anticancer activity of the partially purified protein

The demand for L-asparaginase is predicted to increase several fold in the future due to its potential clinical applications in the treatment of lymphoid system malignancies and leukemia. Thus identifying suitable sources of production should be considered high priority. Fungi are valuable organisms as they are able to convert what would be considered ‘useless’ materials into materials that have potential value. The present study provides a proof of concept of production of a new hyperactive L-asparaginase producer (Rhizopus oryzae AM16), which was successfully isolated and sequentially optimized using a semi solid-state fermentation method with a simple and cheap medium produced from wheat bran (WB). The fungus was able to produce an appreciable amount of the enzyme (2,875.9 U) after 8 days of incubation under 85.7% moisture, in the presence of magnesium nitrate (5.0 mg N/mg nitrogen per gram of dry WB) at pH 5.8. Testing the anticancer activity confirmed the ability of the resultant enzyme to inhibit the growth of various types of cancer cells (HepG2, MCF-7, HCT and A549). The IC₅₀ values of the dialyzed enzyme were lower than that of the crude product. Thus, this newly identified and purified L-asparaginase may be a promising anticancer drug.

Telomere-to-telomere genome assembly of asparaginase-producing Trichoderma simmonsii

BACKGROUND

Trichoderma is a genus of fungi in the family Hypocreaceae and includes species known to produce enzymes with commercial use. They are largely found in soil and terrestrial plants. Recently, Trichoderma simmonsii isolated from decaying bark and decorticated wood was newly identified in the Harzianum clade of Trichoderma. Due to a wide range of applications in agriculture and other industries, genomes of at least 12 Trichoderma spp. have been studied. Moreover, antifungal and enzymatic activities have been extensively characterized in Trichoderma spp. However, the genomic information and bioactivities of T. simmonsii from a particular marine-derived isolate remain largely unknown. While we screened for asparaginase-producing fungi, we observed that T. simmonsii GH-Sj1 strain isolated from edible kelp produced asparaginase. In this study, we report a draft genome of T. simmonsii GH-Sj1 using Illumina and Oxford Nanopore technologies. Furthermore, to facilitate biotechnological applications of this species, RNA-sequencing was performed to elucidate the transcriptional profile of T. simmonsii GH-Sj1 in response to asparaginase-rich conditions.

RESULTS

We generated ~ 14 Gb of sequencing data assembled in a ~ 40 Mb genome. The T. simmonsii GH-Sj1 genome consisted of seven telomere-to-telomere scaffolds with no sequencing gaps, where the N50 length was 6.4 Mb. The total number of protein-coding genes was 13,120, constituting ~ 99% of the genome. The genome harbored 176 tRNAs, which encode a full set of 20 amino acids. In addition, it had an rRNA repeat region consisting of seven repeats of the 18S-ITS1-5.8S-ITS2-26S cluster. The T. simmonsii genome also harbored 7 putative asparaginase-encoding genes with potential medical applications. Using RNA-sequencing analysis, we found that 3 genes among the 7 putative genes were significantly upregulated under asparaginase-rich conditions.

CONCLUSIONS

The genome and transcriptome of T. simmonsii GH-Sj1 established in the current work represent valuable resources for future comparative studies on fungal genomes and asparaginase production.

Distinct functional properties of secretory l-asparaginase Rv1538c involved in phagosomal survival of Mycobacterium tuberculosis

The emergence of drug-resistant Mycobacterium tuberculosis (Mtb) stains has escalated the need for developing more efficient drugs and therapeutic strategies against tuberculosis. Here we functionally annotate a secretory mycobacterial asparaginase Rv1538c (MtA) and describe its biochemical properties. MtA primarily existed as dimer along with a minor population of multimers. Circular dichroism and fluorescence spectroscopy demonstrated a compact structure in Tris HCl buffer at pH 8.0. Under these conditions it also displayed optimum activity. It retained ∼40% activity at pH 5.5, supporting its physiological relevance in acidic phagosomal environment. MtA contravened classical Michaelis-Menten kinetics and exhibited product inhibition profile, yielding a K_cat of 869.4 s^-1 and an apparent K_m of 8.36 mM. We report the presence of several antigenic epitopes and a C-terminal YXXXD/E motif in MtA, hinting towards its potential to interact or influence host immune system. This was supported by our observation of morphological changes in MtA-treated human B lymphoblasts. We propose that MtA is a dual purpose enzyme used by Mtb to survive inside its host by; 1) ammonia-mediated neutralization of the phagosomal acidic pH and 2) inducing stress to primary immune cells and compromising the host immune response. Overall, this study contributes to our understanding of the biological role of mycobacterial asparaginase opening avenues for developing effective TB therapeutics.

L-Asparaginase activity analysis, ansZ gene identification and anticancer activity of a new Bacillus subtilis isolated from sponges of the Red Sea

This study describes the isolation of various marine bacteriafrom sponges collected from the Red Sea (Saudi Arabia) andL-asparaginase (anti-cancer enzyme) production from bacterialisolates. The 16S rDNA based phylogenetic analysis revealed thatthe isolate WSA3 was a Bacillus subtilis. Its partial-length genesequence was submitted to GenBank under the accession numberMK072695. The new B. subtilis strain harbored the exact size(1128 bp) of the new L-asparaginase (ansZ) gene as confirmedby PCR and in gel visualization, which was submitted to the NCBIdatabase (accession number MN566442). The molecular weightof partially purified L-asparaginase was determined as 45 kDa bySDS-PAGE. In addition, the enzyme L-asparaginase did not showglutaminase activity which is very important from a medical pointof view. Moreover, 100 μg/mL of the partially purified B. subtilis Lasparaginaseshowed promising anti-cancer activities when testedagainst three cancer cell lines (HCT-116, MCF-7, and HepG2).

Identification of L-asparaginases from Streptomyces strains with competitive activity and immunogenic profiles: a bioinformatic approach

The enzyme L-asparaginase from Escherichia coli is a therapeutic enzyme that has been a cornerstone in the clinical treatment of acute lymphoblastic leukemia for the last decades. However, treatment effectiveness is limited by the highly immunogenic nature of the protein and its cross-reactivity towards L-glutamine. In this work, a bioinformatic approach was used to identify, select and computationally characterize L-asparaginases from Streptomyces through sequence-based screening analyses, immunoinformatics, homology modeling, and molecular docking studies. Based on its predicted low immunogenicity and excellent enzymatic activity, we selected a previously uncharacterized L-asparaginase from Streptomyces scabrisporus. Furthermore, two putative asparaginase binding sites were identified and a 3D model is proposed. These promising features allow us to propose L-asparaginase from S. scabrisporus as an alternative for the treatment of acute lymphocytic leukemia.

Improving the Treatment of Acute Lymphoblastic Leukemia

l-Asparaginase (EC 3.5.1.1) was first used as a component of combination drug therapies to treat acute lymphoblastic leukemia (ALL), a cancer of the blood and bone marrow, almost 50 years ago. Administering this enzyme to reduce asparagine levels in the blood is a cornerstone of modern clinical protocols for ALL; indeed, this remains the only successful example of a therapy targeted against a specific metabolic weakness in any form of cancer. Three problems, however, constrain the clinical use of l-asparaginase. First, a type II bacterial variant of l-asparaginase is administered to patients, the majority of whom are children, which produces an immune response thereby limiting the time over which the enzyme can be tolerated. Second, l-asparaginase is subject to proteolytic degradation in the blood. Third, toxic side effects are observed, which may be correlated with the l-glutaminase activity of the enzyme. This Perspective will outline how asparagine depletion negatively impacts the growth of leukemic blasts, discuss the structure and mechanism of l-asparaginase, and briefly describe the clinical use of chemically modified forms of clinically useful l-asparaginases, such as Asparlas, which was recently given FDA approval for use in children (babies to young adults) as part of multidrug treatments for ALL. Finally, we review ongoing efforts to engineer l-asparaginase variants with improved therapeutic properties and briefly detail emerging, alternate strategies for the treatment of forms of ALL that are resistant to asparagine depletion.

Multi Gene Genetic Program Modelling on L-Asparaginase Activity of Bacillus Stratosphericus

The current study focuses on maximization of L-Asparaginase production from Bacillus stratosphericus isolated from Ocimum tenuiflorum. Optimization study followed by modelling using Artificial Neural Network (ANN) was performed. The experimental data obtained from Response Surface Methodology (RSM) was further studied by an evolutionary algorithm Genetic Programming (GP) to find the prediction equation. GP does not require prior knowledge of the data sets. GP is an extension of Genetic Algorithm (GA), where the results are represented in the form of trees. Multi gene genetic programming (MGPP) is a variant of GP used to solve non-linear mathematical models. The prediction equation obtained from the GP analysis is represented in the form of tree. Each tree represents single gene. Best fit individuals obtained at each generation by using genetic operators were selected to get better regression co-efficient value. The predicted and experimental data showed good significance with R2 = 0.99956.

Marine microbial L-asparaginase: Biochemistry, molecular approaches and applications in tumor therapy and in food industry

The marine environment is a rich source of biological and chemical diversity. It covers more than 70% of the Earth's surface and features a wide diversity of habitats, often displaying extreme conditions, where marine organisms thrive, offering a vast pool for microorganisms and enzymes. Given the dissimilarity between marine and terrestrial habitats, enzymes and microorganisms, either novel or with different and appealing features as compared to terrestrial counterparts, may be identified and isolated. L-asparaginase (E.C. 3.5.1.1), is among the relevant enzymes that can be obtained from marine sources. This amidohydrolase acts on L-asparagine and produce L-aspartate and ammonia, accordingly it has an acknowledged chemotherapeutic application, namely in acute lymphoblastic leukemia. Moreover, L-asparaginase is also of interest in the food industry as it prevents acrylamide formation. Terrestrial organisms have been largely tapped for L-asparaginases, but most failed to comply with criteria for practical applications, whereas marine sources have only been marginally screened. This work provides an overview on the relevant features of this enzyme and the framework for its application, with a clear emphasis on the use of L-asparaginase from marine sources. The review envisages to highlight the unique properties of marine L-asparaginases that could make them good candidates for medical applications and industries, especially in food safety.

l-Asparaginase-mediated downregulation of c-Myc promotes 1,25(OH)2 D3 -induced myeloid differentiation in acute myeloid leukemia cells

Treatment of acute myeloid leukemia (AML) largely depends on chemotherapy, but current regimens have been unsatisfactory for long-term remission. Although differentiation induction therapy utilizing 1,25(OH)₂ D₃ (VD3) has shown great promise for the improvement of AML treatment efficacy, severe side effects caused by its supraphysiological dose limit its clinical application. Here we investigated the combinatorial effect of l-asparaginase (ASNase)-mediated amino acid depletion and the latent alternation of VD3 activity on the induction of myeloid differentiation. ASNase treatment enhanced VD3-driven phenotypic and functional differentiation of three-different AML cell lines into monocyte/macrophages, along with c-Myc downregulation. Using gene silencing with shRNA and a chemical blocker, we found that reduced c-Myc is a critical factor for improving VD3 efficacy. c-Myc-dependent inhibition of mTORC1 signaling and induction of autophagy were involved in the enhanced AML cell differentiation. In addition, in a postculture of AML cells after each treatment, ASNase supports the antileukemic effect of VD3 by inhibiting cell growth and inducing apoptosis. Finally, we confirmed that the administration of ASNase significantly improved VD3 efficacy in the prolongation of survival time in mice bearing tumor xenograft. Our results are the first to demonstrate the extended application of ASNase, which is currently used for acute lymphoid leukemia, in VD3-mediated differentiation induction therapy for AML, and suggest that this drug combination may be a promising novel strategy for curing AML.

Genome Sequence of the Multiple-Protease-Producing Strain Geobacillus thermoleovorans N7, a Thermophilic Bacterium Isolated from Paniphala Hot Spring, West Bengal, India

Here, we present the draft genome sequence of Geobacillus thermoleovorans strain N7 (MCC 3175), isolated from Paniphala Hot Spring, West Bengal, India, which contains genes that encode several industrially and medically important thermostable enzymes like neutral protease, xylose isomerase, rhamnogalacturonan acetylesterase, nitrate and nitrite reductase, l-asparaginase, glutaminase, and RNase P.

Marine Microorganism: An Underexplored Source of l-Asparaginase

l-Asparaginase (EC 3.5.1.1) is an enzyme that catalyzes the hydrolysis of l-asparagine to l-aspartic acid. This enzyme has an important role in medicine and food. l-Asparaginase is a potential drug in cancer therapy. Furthermore, it is also applied for reducing acrylamide, a carcinogenic compound in baked and fried foods. Until now, approved l-asparaginases for both applications are few due to their lack of appropriate properties. As a result, researchers have been enthusiastically seeking new sources of enzyme with better performance. A great number of terrestrial l-asparaginase-producing microorganisms have been reported but unfortunately, almost all failed to meet criteria for cancer therapy and acrylamide reducing agent. As a largest area than Earth, marine environment, by contrast, has not been optimally explored yet. So far, a great challenge facing an exploration of marine microorganisms is mainly due to their harsh, mysterious, and dangerous environment. It is clear that marine environment, a gigantic potential source for marine natural products is scantily revealed, although several approaches and technologies have been developed. This chapter presents the historical of l-asparaginase discovery and applications. It is also discussed, how the marine environment, even though offering a great potency but is still one of the less explored area for l-asparaginase-producing microorganisms.

Design and Characterization of Erwinia Chrysanthemi l-Asparaginase Variants with Diminished l-Glutaminase Activity

Current FDA-approved l-asparaginases also possess significant l-glutaminase activity, which correlates with many of the toxic side effects of these drugs. Therefore, l-asparaginases with reduced l-glutaminase activity are predicted to be safer. We exploited our recently described structures of the Erwinia chrysanthemi l-asparaginase (ErA) to inform the design of mutants with diminished ability to hydrolyze l-glutamine. Structural analysis of these variants provides insight into the molecular basis for the increased l-asparagine specificity. A primary role is attributed to the E63Q mutation that acts to hinder the correct positioning of l-glutamine but not l-asparagine. The substitution of Ser-254 with either an asparagine or a glutamine increases the l-asparagine specificity but only when combined with the E63Q mutation. The A31I mutation reduces the substrate Km value; this is a key property to allow the required therapeutic l-asparagine depletion. Significantly, an ultra-low l-glutaminase ErA variant maintained its cell killing ability. By diminishing the l-glutaminase activity of these highly active l-asparaginases, our engineered ErA variants hold promise as l-asparaginases with fewer side effects.

Purification and Characterization of Glutaminase Free Asparaginase from Enterobacter cloacae: In-Vitro Evaluation of Cytotoxic Potential against Human Myeloid Leukemia HL-60 Cells

Asparaginase is an important antileukemic agent extensively used worldwide but the intrinsic glutaminase activity of this enzymatic drug is responsible for serious life threatening side effects. Hence, glutaminase free asparaginase is much needed for upgradation of therapeutic index of asparaginase therapy. In the present study, glutaminase free asparaginase produced from Enterobacter cloacae was purified to apparent homogeneity. The purified enzyme was found to be homodimer of approximately 106 kDa with monomeric size of approximately 52 kDa and pI 4.5. Purified enzyme showed optimum activity between pH 7-8 and temperature 35-40°C, which is close to the internal environment of human body. Monovalent cations such as Na+ and K+ enhanced asparaginase activity whereas divalent and trivalent cations, Ca2+, Mg2+, Zn2+, Mn2+, and Fe3+ inhibited the enzyme activity. Kinetic parameters Km, Vmax and Kcat of purified enzyme were found to be 1.58×10-3 M, 2.22 IU μg-1 and 5.3 × 104 S-1, respectively. Purified enzyme showed prolonged in vitro serum (T1/2 = ~ 39 h) and trypsin (T1/2 = ~ 32 min) half life, which is therapeutically remarkable feature. The cytotoxic activity of enzyme was examined against a panel of human cancer cell lines, HL-60, MOLT-4, MDA-MB-231 and T47D, and highest cytotoxicity observed against HL-60 cells (IC50 ~ 3.1 IU ml-1), which was comparable to commercial asparaginase. Cell and nuclear morphological studies of HL-60 cells showed that on treatment with purified asparaginase symptoms of apoptosis were increased in dose dependent manner. Cell cycle progression analysis indicates that enzyme induces apoptosis by cell cycle arrest in G0/G1 phase. Mitochondrial membrane potential loss showed that enzyme also triggers the mitochondrial pathway of apoptosis. Furthermore, the enzyme was found to be nontoxic for human noncancerous cells FR-2 and nonhemolytic for human erythrocytes.

L-asparaginase as a critical component to combat Acute Lymphoblastic Leukaemia (ALL): A novel approach to target ALL

L-asparaginase, an anti-leukaemic drug that has been approved for clinical use for many years in the treatment of childhood Acute Lymphoblastic Leukaemia (ALL), is obtained from bacterial origin (Escherichia coli and Erwinia carotovora). The efficacy of L-asparaginase has been discussed for the past 40 years, and an ideal substitute for the enzyme has not yet been developed. The early clearance from plasma (short half-life) and requirement for multiple administrations and hence frequent physician visits make the overall treatment cost quite high. In addition, a high rate of allergic reactions in patients receiving treatment with the enzyme isolated from bacterial sources make its clinical application challenging. For these reasons, various attempts are being made to overcome these barriers. Therefore, the present article reviews studies focused on seeking substitutes for L-asparaginase through alternative sources including bacteria, fungi, actinomycetes, algae and plants to overcome these limitations. In addition, the role of chemical modifications and protein engineering approaches to enhance the drug's efficacy are also discussed. Moreover, an overview has also been provided in the current review regarding the contradiction among various researchers regarding the significance of the enzyme's glutaminase activity.

Industrial effluent as a substrate for glutaminase freel-asparaginase production from Pseudomonas plecoglossicida strain RS1; media optimization, enzyme purification and its characterization

Glutaminase freel-asparaginase production byPseudomonas plecoglossicidaRS1 using industrial effluent as a substrate: media optimization, enzyme purification and its characterization.

Topotecan combined with Ifosfamide, Etoposide, and L-asparaginase (TIEL) regimen improves outcomes in aggressive T-cell lymphoma

This study evaluated the efficacy and safety of a new regimen consisting of Topotecan, Ifosfamide, Etoposide, and L-asparaginase (TIEL) in treating aggressive T-cell lymphoma. Twenty-four patients were included in the research, eighteen males and six females. Half of the patients were in stages III and IV, and nearly half of them experienced failure of at least one regimen. Eleven were diagnosed as peripheral T-cell lymphoma (PTCL), five extranodal NK/T-cell lymphoma, non-specific, four angioimmunoblastic, and four anaplastic large-cell lymphoma (2 ALK positive). Patients were given 98 cycles of TIEL altogether. The responsive rate to TIEL was 76.9 % among 13 cases who received the regimen as the first-line treatment. Among 11 cases, TIEL was the second- or more-line treatment, the responsive rate was 63.6 %. The median PFS was 32.0 ± 21.0 (95 % CI 0-73.29) months. Median overall survival (OS) was not reached yet. Approximately 41.3 % of patients showed the third- to fourth-degree hematological side effects. Non-hematological toxicity included nausea, vomiting, diarrhea, and abnormal liver function. Among those patients received L-asparaginase, nine experienced mild abnormal coagulation function after 7 days of initiating chemotherapy, and no pancreatic injury was found. TIEL regimen is effective for aggressive T-cell lymphoma with controllable side effect and can be used for more patients.

Characterization of a recombinant glutaminase-free L-asparaginase (ansA3) enzyme with high catalytic activity from Bacillus licheniformis

L-Asparaginase (3.5.1.1) is an enzyme widely used to treat the acute lymphoblastic leukemia. Two genes coding for L-asparaginase (ansA1 and ansA3) from Bacillus licheniformis MTCC 429 were cloned and overexpressed in Escherichia coli BL21 (DE3) cells. The recombinant proteins were purified to homogeneity by one-step purification process and further characterized for various biochemical parameters. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that both the enzymes are monomers of ∼37 kDa. Recombinant ansA1 was found to be highly unstable, and recombinant ansA3 was catalytically active and stable, which showed an optimum activity of 407.65 IU/mg at 37 °C and pH 8. Recombinant ansA3 showed higher substrate specificity for L-asparagine with negligible glutaminase activity. Kinetic parameters like K m , V max, k cat, and k cat/K m were calculated for recombinant ansA3.

Asparaginase unveils glutamine-addicted AML

In this issue of Blood, Willems et al describe the dependence of acute myeloid leukemia (AML) cells on glutamine for maintaining protein synthesis downstream of mammalian target of rapamycin (mTOR) and show that the enzyme asparaginase can be used to target this dependence. Using various AML cell lines, primary samples, and CD341 stem cells from healthy donors, the authors support the notion that asparaginase may offer a therapeutic benefit in AML—not from its well-known enzymatic activity, but from its “off-target” effects on glutamine levels that result in inhibition of downstream mTOR signaling, inhibition of protein synthesis, and ultimately loss of viability.

Biochemical characterization of a novel L-Asparaginase with low glutaminase activity from Rhizomucor miehei and its application in food safety and leukemia treatment

A novel fungal gene encoding the Rhizomucor miehei l-asparaginase (RmAsnase) was cloned and expressed in Escherichia coli. Its deduced amino acid sequence shared only 57% identity with the amino acid sequences of other reported l-asparaginases. The purified l-asparaginase homodimer had a molecular mass of 133.7 kDa, a high specific activity of 1,985 U/mg, and very low glutaminase activity. RmAsnase was optimally active at pH 7.0 and 45°C and was stable at this temperature for 30 min. The final level of acrylamide in biscuits and bread was decreased by about 81.6% and 94.2%, respectively, upon treatment with 10 U RmAsnase per mg flour. Moreover, this l-asparaginase was found to potentiate a lectin's induction of leukemic K562 cell apoptosis, allowing lowering of the drug dosage and shortening of the incubation time. Overall, our findings suggest that RmAsnase possesses a remarkable potential for the food industry and in chemotherapeutics for leukemia.

Glutaminase regulation in cancer cells: a druggable chain of events

Metabolism is the process by which cells convert relatively simple extracellular nutrients into energy and building blocks necessary for their growth and survival. In cancer cells, metabolism is dramatically altered compared with normal cells. These alterations are known as the Warburg effect. One consequence of these changes is cellular addiction to glutamine. Because of this, in recent years the enzyme glutaminase has become a key target for small molecule therapeutic intervention. Like many oncotargets, however, glutaminase has a number of upstream partners that might offer additional druggable targets. This review summarizes the work from the current decade surrounding glutaminase and its regulation, and suggests strategies for therapeutic intervention in relevant cases.