Identification of CRASH, a gene deregulated in gynecological tumors

We have identified CRASH, a human asparaginase-like protein which is composed of 308 amino acids and exhibits 32% homology to human aspartylglucosaminadase at the amino acid level. Database analysis revealed that the gene corresponding to CRASH is composed of 7 exons and 6 introns. Steady-state level of CRASH mRNA was found to be increased in 5 cell lines derived from metastatic lesions compared with 2 cell lines derived from primary mammary carcinoma and HMEC (human mammary epithelial cells). We found that the mRNA level of CRASH correlates with the metastatic propensity of several isogenic human colon cancer and pancreatic carcinoma cell lines. CRASH corresponds to a recently identified sperm autoantigen and furthermore we have demonstrated inducibility of CRASH mRNA by androgen and progesterone. Investigation of several types of human cancers and their corresponding normal tissues revealed high levels of CRASH mRNA in uterine, mammary and ovarian tumors compared with the corresponding normal tissues. CRASH mRNA expression was analysed in breast cancer samples with disclosed clinico-pathological features and corresponding normal tissues. The levels of CRASH mRNA were significantly up-regulated in tumors compared with normal breast tissues and correlate with lack of estrogen receptor expression of the tumors.

Molecular characterization of the soybean L-asparaginase gene induced by low temperature stress

L-asparaginase (EC 3.5.1.1) catalyzes the hydrolysis of the amide group of L-asparagine, releasing aspartate and NH4+. We isolated a low temperature-inducible cDNA sequence encoding L-asparaginase from soybean leaves. The full-length L-asparaginase cDNA, designated GmASP1, contains an open reading frame of 1,258 bp coding for a protein of 326 amino acids. Genomic DNA blotting and fluorescence in situ hybridization showed that the soybean genome has two copies of GmASP1. GmASP1 mRNA was induced by low temperature, ABA and NaCl, but not by heat shock or drought stress. E. coli cells expressing recombinant GmASP1 had 3-fold increased L-asparaginase activity. A possible function of L-asparaginase in the early response to low temperature stress is discussed.

A Mouse Model with Ablated Asparaginase and Isoaspartyl Peptidase 1 (Asrgl1) Develops Early Onset Retinal Degeneration (RD) Recapitulating the Human Phenotype

We previously identified a homozygous G178R mutation in human ASRGL1 (hASRGL1) through whole-exome analysis responsible for early onset retinal degeneration (RD) in patients with cone-rod dystrophy. The mutant G178R ASRGL1 expressed in Cos-7 cells showed altered localization, while the mutant ASRGL1 in E. coli lacked the autocatalytic activity needed to generate the active protein. To evaluate the effect of impaired ASRGL1 function on the retina in vivo, we generated a mouse model with c.578_579insAGAAA (NM_001083926.2) mutation (Asrgl1mut/mut) through the CRISPR/Cas9 methodology. The expression of ASGRL1 and its asparaginase activity were undetectable in the retina of Asrgl1mut/mut mice. The ophthalmic evaluation of Asrgl1mut/mut mice showed a significant and progressive decrease in scotopic electroretinographic (ERG) response observed at an early age of 3 months followed by a decrease in photopic response around 5 months compared with age-matched wildtype mice. Immunostaining and RT-PCR analyses with rod and cone cell markers revealed a loss of cone outer segments and a significant decrease in the expression of Rhodopsin, Opn1sw, and Opn1mw at 3 months in Asrgl1mut/mut mice compared with age-matched wildtype mice. Importantly, the retinal phenotype of Asrgl1mut/mut mice is consistent with the phenotype observed in patients harboring the G178R mutation in ASRGL1 confirming a critical role of ASRGL1 in the retina and the contribution of ASRGL1 mutations in retinal degeneration.

Towards development of biobetter: L-asparaginase a case study

BACKGROUND

L-asparaginase (ASNase) has played a key role in the management of acute lymphoblastic leukaemia (ALL). As an amidohydrolase, it catalyzes the hydrolysis of L-asparagine, a crucial step in the treatment of ALL. Various ASNase variants have evolved from diverse sources since it was first used in paediatric patients in the 1960s. This review describes the available ASNase and approaches being used to develop ASNase as a biobetter candidate.

SCOPE OF REVIEW

The review discusses the Glycosylation and PEGylation techniques, which are frequently used to develop biobetter versions of the majority of the therapeutic proteins. Further, it explores current ASNase biobetters in therapeutic use and discusses the protein engineering and chemical modification approaches that were employed to reduce immunogenicity, extend protein half-life, and enhance protease stability of ASNase. Emerging strategies like immobilization and encapsulation are also highlighted as potential pathways for improving ASNase properties.

MAJOR CONCLUSIONS

The purpose of the development of ASNase biobetter is to achieve a novel therapeutic candidate that could improve catalytic efficiency, in vivo stability with minimum glutaminase (GLNase) activity and toxicity. Modification of ASNase by immobilization and encapsulation or by fusion technologies like Albumin fusion, Fc fusion, ELP fusion, XTEN fusion, etc. can be exploited to develop a novel biobetter candidate suitable for therapeutic approaches.

GENERAL SIGNIFICANCE

This review emphasizes the importance of biobetter development for therapeutic proteins like ASNase. Improved ASNase molecules have the potential to significantly advance the treatment of ALL and have broader implications in the pharmaceutical industry.

Characterization of the impact of the MYBBP1A gene and rs3809849 on asparaginase sensitivity and cellular functions

Aims: To investigate the role of MYBBP1A gene and rs3809849 in pancreatic cancer (PANC1) and lymphoblastic leukemia (NALM6) cell lines and their response to asparaginase treatment. Materials & methods: The authors applied CRISPR-Cas9 to produce MYBBP1A knock-out (KO) and rs3809849 knock-in (KI) cell lines. The authors also interrogated rs3809849's impact on PANC1 cells through allele-specific overexpression. Results: PANC1 MYBBP1A KO cells exhibited lower proliferation capacity (p ≤ 0.05), higher asparaginase sensitivity (p = 0.01), reduced colony-forming potential (p = 0.001), cell cycle blockage in S phase, induction of apoptosis and remarkable morphology changes suggestive of an epithelial-mesenchymal transition. Overexpression of the wild-type (but not the mutant) allele of MYBBP1A-rs3809849 in PANC1 cells increased asparaginase sensitivity. NALM6 MYBBP1A KO displayed resistance to asparaginase (p < 0.0001), whereas no effect for rs3809849 KI was noted. Conclusions:MYBBP1A is important for regulating various cellular functions, and it plays, along with its rs3809849 polymorphism, a tissue-specific role in asparaginase treatment response.

Enhanced expression of halp gene confers cellular resistance to H2O2 induced senescence

OBJECTIVE

To investigate the H2O2-induced expression of human histone acetyltransferase-like protein (hALP), a telomerase regulation-associated gene, and its effects on the stress-triggered cellular senescence.

METHODS

The induced expression of hALP was measured by semi-quantitative RT-PCR and immunofluorescent histochemistry after treatment of HeLa cells by H2O2. The effects of hALP expression on cellular responses to H2O2 were analyzed by MTT, flowcytometry, and SA-beta-gal staining, respectively.

RESULTS

hALP mRNA could be dose-dependently induced by treatments of 0.2-1.6 mmol/L H2O2, and the induction could be observed after 6 hours and kept for 36 hours in the presence of 0.4 mmol/L H2O2. Meanwhile, the immunofluorescent staining showed marked stronger nuclear intensity of hALP protein in H2O2-treated HeLa cells. In the treatment of H2O2, the ectopic expression of hALP enhanced continuous growth and overcame G2/M arrest as well as decreased senescence-associated beta-gal staining. On the contrary, the transfected clones with antisense or blank vector and original He-La cells presented growth suppression, G2/M delay and higher percentage of SA-beta-gal activities in the presence of H2O2.

CONCLUSIONS

The expression of hALP could be up-regulated by treatment of H2O2, and elevated expression could enhance cellular resistance to H2O2-induced cellular senescence. The data might be of references to elucidation of basic biological function of hALP gene and its associated telomerase activity.

[An analysis of induced expression and function of telomerase-regulation associated hALP gene on genotoxic agents]

OBJECTIVE

To confirm the responses and function of hALP, a telomerase-regulation associated gene, in DNA damage.

METHODS

HeLa and Hep2 cells were treated by genotoxic agents H2O2 and cisplatin, and the induced expression of hALP was measured by quantitative RT-PCR and immunofluorescent histochemistry. The alterations in transcriptional activity of hALP promoter were estimated by luciferase reporter assays. The effects of genotoxic agents on cells in different status of hALP expression were analyzed by MTT method.

RESULTS

The level of hALP mRNA could be increased when treated by 0.2 - 1.6 mmol/L H2O2 and reach a peak in concentration of 0.4 mmol/L. The induction could be observed after 6 h in the treatment of 0.4 mmol/L H2O2 and the higher level can be retained for 36 h. Similarly, cisplatin induced hALP mRNA expression is also dose and time dependent. The immunofluorescent staining showed that the treatment of 0.2 or 0.4 mmol/L H2O2, 0.2 or 0.5 micromol/L cisplatin increased the intensity of hALP protein in cellular nuclei. The luciferase assays demonstrated that both H2O2 and cisplatin could up-regulate hALP promoter activity through its upstream - 705 - +20 nt region. In cell survivor assay, the HeLa cells expressing sense hALP gene could grow continuously in the presence of 0.4 mmol/L H2O2 or 0. 5 micromol/L cisplatin while cells with antisense hALP or control cells were slower in growth.

CONCLUSIONS

The expression of hALP gene could be up-regulated by DNA damage through activating transcription of its promoter, and increase cellular resistance to genotoxic agents.

Controlling enzyme activity by mutagenesis and metal exchange to obtain crystal structures of stable substrate complexes of Class 3 l-asparaginase

Rhizobium etli is a nitrogen-fixing bacterium that encodes two l-asparaginases. The structure of the inducible R. etli asparaginase ReAV has been recently determined to reveal a protein with no similarity to known enzymes with l-asparaginase activity, but showing a curious resemblance to glutaminases and β-lactamases. The uniqueness of the ReAV sequence and 3D structure make the enzyme an interesting candidate as potential replacement for the immunogenic bacterial-type asparaginases that are currently in use for the treatment of acute lymphoblastic leukemia. The detailed catalytic mechanism of ReAV is still unknown; therefore, the enzyme was subjected to mutagenetic experiments to investigate its catalytic apparatus. In this work, we generated two ReAV variants of the conserved Lys138 residue (K138A and K138H) that is involved in zinc coordination in the wild-type protein and studied them kinetically and structurally. We established that the activity of wild-type ReAV and the generated variants is significantly reduced in the presence of Cd2+ cations, which slow down the proteins while improving their apparent substrate affinity. Moreover, the inhibitory effect of Cd2+ is enhanced by the substitutions of Lys138, which disrupt the metal coordination sphere. The proteins with impaired activity but increased affinity were cocrystallized with the L-Asn substrate. Here, we present the crystal structures of wild-type ReAV and its K138A and K138H variants, unambiguously revealing bound l-asparagine in the active site. After careful analysis of the stereochemistry of the nucleophilic attack, we assign the role of the primary nucleophile of ReAV to Ser48. Furthermore, we propose that the reaction catalyzed by ReAV proceeds according to a double-displacement mechanism.

[Nucleolar localization of human acetyltransferase-like protein and its expression in tumors]

OBJECTIVE

To confirm the nucleolar localization of telomerase-regulation associated protein-human N-acetyltransferase-like protein (hALP) and its associated functions.

METHODS

Immunofluoresent staining and immunoelectron microscopy were used to detect the distribution of hALP in HeLa and Saos2 cells, and the co-localization of hALP and rDNA was analyzed by fluorescence in situ hybridization and immunofluoresence. RNAi was performed to further verify the nucleolar localization of hALP. A series of eukaryotic expression plasmids carrying various portions of hALP sequence were constructed and transiently transfected to HeLa and Saos2 cells. The expression of hALP in tumor tissues was stained by immunohistochemistry.

RESULTS

hALP distributed predominantly in the nucleoli of HeLa and Saos2 cells, and colocalized with rDNA. Granular component was the precise distribution of hALP in the nucleolus under electron microscope. Nucleolar signals for hALP reduced significantly in cells transfected with hALP siRNA. The carboxy terminus of hALP including residues 549-834 was necessary for its nucleolar localization. hALP could be detected in the nucleoli of many kinds of tumor cells, including leiomyosarcoma, primitive neuroectodermal tumor, neuroblastoma, melanoma, prostatic cancer, and clear cell renal carcinoma.

CONCLUSION

hALP is a nucleolar protein, and the nucleolar localization is mediated by its carboxy terminal domain, and hALP could be detected in the nucleoli of many tumor tissues, which is worthy of further investigation.

Optimizing recombinant production of L-asparaginase 1 from Saccharomyces cerevisiae using response surface methodology

L-asparaginase is an essential enzyme used in cancer treatment, but its production faces challenges like low yield, high cost, and immunogenicity. Recombinant production is a promising method to overcome these limitations. In this study, response surface methodology (RSM) was used to optimize the production of L-asparaginase 1 from Saccharomyces cerevisiae in Escherichia coli K-12 BW25113. The Box-Behnken design (BBD) was utilized for the RSM modeling, and a total of 29 experiments were conducted. These experiments aimed to examine the impact of different factors, including the concentration of isopropyl-b-LD-thiogalactopyranoside (IPTG), the cell density prior to induction, the duration of induction, and the temperature, on the expression level of L-asparaginase 1. The results revealed that while the post-induction temperature, cell density at induction time, and post-induction time all had a significant influence on the response, the post-induction time exhibited the greatest effect. The optimized conditions (induction at cell density 0.8 with 0.7 mM IPTG for 4 h at 30 °C) resulted in a significant amount of L-asparaginase with a titer of 93.52 μg/mL, which was consistent with the model-based prediction. The study concluded that RSM optimization effectively increased the production of L-asparaginase 1 in E. coli, which could have the potential for large-scale fermentation. Further research can explore using other host cells, optimizing the fermentation process, and examining the effect of other variables to increase production.

Supramolecular assembly of GSK3α as a cellular response to amino acid starvation

The tolerance of amino acid starvation is fundamental to robust cellular fitness. Asparagine depletion is lethal to some cancer cells, a vulnerability that can be exploited clinically. We report that resistance to asparagine starvation is uniquely dependent on an N-terminal low-complexity domain of GSK3α, which its paralog GSK3β lacks. In response to depletion of specific amino acids, including asparagine, leucine, and valine, this domain mediates supramolecular assembly of GSK3α with ubiquitin-proteasome system components in spatially sequestered cytoplasmic bodies. This effect is independent of mTORC1 or GCN2. In normal cells, GSK3α promotes survival during essential amino acid starvation. In human leukemia, GSK3α body formation predicts asparaginase resistance, and sensitivity to asparaginase combined with a GSK3α inhibitor. We propose that GSK3α body formation provides a cellular mechanism to maximize the catalytic efficiency of proteasomal protein degradation in response to amino acid starvation, an adaptive response co-opted by cancer cells for asparaginase resistance.

Enhancing the Catalytic Activity of Thermo-Asparaginase from Thermococcus sibiricus by a Double Mesophilic-like Mutation in the Substrate-Binding Region

L-asparaginases (L-ASNases) of microbial origin are the mainstay of blood cancer treatment. Numerous attempts have been performed for genetic improvement of the main properties of these enzymes. The substrate-binding Ser residue is highly conserved in L-ASNases regardless of their origin or type. However, the residues adjacent to the substrate-binding Ser differ between mesophilic and thermophilic L-ASNases. Based on our suggestion that the triad, including substrate-binding Ser, either GSQ for meso-ASNase or DST for thermo-ASNase, is tuned for efficient substrate binding, we constructed a double mutant of thermophilic L-ASNase from Thermococcus sibiricus (TsA) with a mesophilic-like GSQ combination. In this study, the conjoint substitution of two residues adjacent to the substrate-binding Ser55 resulted in a significant increase in the activity of the double mutant, reaching 240% of the wild-type enzyme activity at the optimum temperature of 90 °C. The mesophilic-like GSQ combination in the rigid structure of the thermophilic L-ASNase appears to be more efficient in balancing substrate binding and conformational flexibility of the enzyme. Along with increased activity, the TsA D54G/T56Q double mutant exhibited enhanced cytotoxic activity against cancer cell lines with IC90 values from 2.8- to 7.4-fold lower than that of the wild-type enzyme.

Why a "benign" mutation kills enzyme activity. Structure-based analysis of the A176V mutant of Saccharomyces cerevisiae L-asparaginase I

A conservative and apparently harmless A176V mutation in intracellular S. cerevisiae L-asparaginase (ScerAI) completely abolishes the enzyme activity. Sequence and structural comparisons with type II bacterial L-asparaginases show that the mutated residue is in a very conservative region and plays a vital role in the cohesion of functional tetramers of these enzymes through participation in side-chain...main-chain (Ser) Oy...O (Ala) hydrogen bonds across the tetramer interface. The fact that bacterial L-asparaginases of type I show less conservation in this region suggests that they may have different quaternary structure while adopting the subunit fold and intimate dimer architecture of type II enzymes. A comparison of all available sequences of microbial L-asparaginases confirms that separate intra- and extra-cellular enzymes evolved in prokaryotes and eukaryotes independently. However, an analysis of the available complete genome sequences reveals a surprising fact that Haemophilus influenzae possesses only a type II asparaginase while the archaebacterium Methanococcus jannaschii has a type I gene, but not a type II.

[PEGylated recombinant L-asparaginase from Erwinia carotovora: Production, properties, and potential applications]

N-hydroxysuccinimide ester of monomethoxy polyethylene glycol hemisuccinate was synthesized. It acylated amino groups in a molecule of recombinant L-asparaginase from Erwinia carotovora. A method of L-asparaginase modification by the obtained activated polyethylene glycol derivative was developed. The best results were produced by modification of the enzyme with a 25-fold excess of reagent relative to the enzyme tetramer. The modified L-asparaginase was isolated from the reaction mixture by gel filtration on Sepharose CL-6B. The purified bioconjugate did not contain PEG unbound to the protein, demonstrated high catalytic activity, and exhibited antiproliferative action on cell cultures.

Dissecting dual specificity: Identifying key residues in L-asparaginase for enhanced acute lymphoid leukemia therapy and reduced adverse effects

L-asparaginase from Escherichia coli (EcA) has been used for the treatment of acute lymphoid leukemia (ALL) since the 1970s. Nevertheless, the enzyme has a second specificity that results in glutaminase breakdown, resulting in depletion from the patient's body, causing severe adverse effects. Despite the huge interest in the use of this enzyme, the exact process of glutamine depletion is still unknown and there is no consensus regarding L-asparagine hydrolysis. Here, we investigate the role of T12, Y25, and T89 in asparaginase and glutaminase activities. We obtained individual clones containing mutations in the T12, Y25 or T89 residues. After the recombinant production of wild-type and mutated EcA, The purified samples were subjected to structural analysis using Nano Differential Scanning Fluorimetry, which revealed that all samples contained thermostable molecules in their active structural conformation, the homotetramer conformation. The quaternary conformation was confirmed by DLS and SEC. The activity enzymatic assay combined with molecular dynamics simulation identified the contribution of T12, Y25, and T89 residues in EcA glutaminase and asparaginase activities. Our results mapped the enzymatic behavior paving the way for the designing of improved EcA enzymes, which is important in the treatment of ALL.

Cell growth stimulation by CRASH, an asparaginase-like protein overexpressed in human tumors and metastatic breast cancers

The gene encoding CRASH, a human asparaginase-like protein, has been cloned and its transcriptional activation has been detected in gynecologic cancers. To define the expression of CRASH in human tumors and its possible functional role, monoclonal antibodies against the CRASH protein have been generated. In non-transformed tissues CRASH was only detected in testis, brain, esophagus, prostate and proliferating endometrium. On the other hand, 36/50 ovarian carcinomas, 16/78 mammary carcinomas, 6/6 uroepithelial bladder carcinomas and 5/33 colon carcinomas scored positive for CRASH, with the absence of reactivity in the corresponding normal tissues. Strikingly, 11 out of the 16 breast cancers that expressed CRASH were metastatic, nominating CRASH to be functionally relevant in tumor progression. Twenty-eight out of 42 endometrium tumors expressed CRASH at high levels as did 5/41 prostate carcinomas, as well as ovary and breast cancers, indicating a regulation of CRASH expression by sex hormones. A bona fide estrogen responsive element was detected at bases -201/-183. This proved to be highly preserved across species, supporting an actual functional role. Asparaginase-like proteins play a role in growth regulation and signaling by p70 S6 kinase. The somatic knock-out of CRASH resulted in significant inhibition of growth of KM12L4A colon carcinoma cells, which abundantly express CRASH, whereas the proliferation of the syngeneic, weakly-expressing, slowly-growing KL12SM was not affected. These results are consistent with a selective growth advantage for aggressive cancers expressing CRASH, and nominate CRASH as a novel diagnostic and therapeutic tumor target.

L-Asparaginase from Lachancea Thermotolerans: Effect of Lys99Ala on Enzyme Performance and in vitro Antileukemic Efficacy

L-asparaginases (EC 3.5.1.1) are amidohydrolase enzymes that predominantly catalyze conversion of L-asparagine to L-aspartic acid and ammonia. In addition, some exhibit secondary L-glutaminase activity. Escherichia coli and Erwinia chrysanthemi L-asparaginases are widely used in the pharmaceutical industry to produce therapeutically important compounds. In the therapeutic use of enzymes, bacterial L-asparaginases can trigger immune responses, leading to a high rate of adverse effects that diminish the effectiveness of the treatment. This situation has forced scientists to search for promising L-asparaginases from new sources. Yeast L-asparaginases could be useful in reducing toxicity and enhancing efficacy but they have been poorly studied to date. Here, we characterized the yeast Lachancea thermotolerans L-asparaginase (LtASNase) purified by affinity chromatography. It has a specific activity of 313.8 U/mg and a high kcat value (312.4 s). We demonstrated through a semi-rational design that the mutations of Lys99 show varying effects on catalytic activity, with the Lys99Ala mutant increasing specific activity 3.3-fold. Furthermore, the in vitro antileukemic activity of the non-formulated form of Lys99Ala LtASNase was evaluated against SUP-B15 and REH cell lines. The results demonstrated that LtASNase exhibits significant antileukemic potential, comparable to commercial type II bacterial enzymes. The understanding of the mutant L-asparaginases examined in this study will significantly contribute to the development of new and more effective yeast-derived asparaginases.

Improving the production of recombinant L-Asparaginase-II in Escherichia coli by co-expressing catabolite repressor activator (cra) gene

Identification of a single genetic target for microbial strain improvement is difficult due to the complexity of the genetic regulatory network. Hence, a more practical approach is to identify bottlenecks in the regulatory networks that control critical metabolic pathways. The present work focuses on enhancing cellular physiology by increasing the metabolic flux through the central carbon metabolic pathway. Global regulator cra (catabolite repressor activator), a DNA-binding transcriptional dual regulator was selected for the study as it controls the expression of a large number of operons that modulate central carbon metabolism. To upregulate the activity of central carbon metabolism, the cra gene was co-expressed using a plasmid-based system. Co-expression of cra led to a 17% increase in the production of model recombinant protein L-Asparaginase-II. A pulse addition of 0.36% of glycerol every two hours post-induction, further increased the production of L-Asparaginase-II by 35% as compared to the control strain expressing only recombinant protein. This work exemplifies that upregulating the activity of central carbon metabolism by tuning the expression of regulatory genes like cra can relieve the host from cellular stress and thereby promote the growth as well as expression of recombinant hosts.

Nonclinical Evaluation of Single-Mutant E. coli Asparaginases Obtained by Double-Mutant Deconvolution: Improving Toxicological, Immune and Inflammatory Responses

Acute lymphoblastic leukaemia is currently treated with bacterial L-asparaginase; however, its side effects raise the need for the development of improved and efficient novel enzymes. Previously, we obtained low anti-asparaginase antibody production and high serum enzyme half-life in mice treated with the P40S/S206C mutant; however, its specific activity was significantly reduced. Thus, our aim was to test single mutants, S206C and P40S, through in vitro and in vivo assays. Our results showed that the drop in specific activity was caused by P40S substitution. In addition, our single mutants were highly stable in biological environment simulation, unlike the double-mutant P40S/S206C. The in vitro cell viability assay demonstrated that mutant enzymes have a higher cytotoxic effect than WT on T-cell-derived ALL and on some solid cancer cell lines. The in vivo assays were performed in mice to identify toxicological effects, to evoke immunological responses and to study the enzymes' pharmacokinetics. From these tests, none of the enzymes was toxic; however, S206C elicited lower physiological changes and immune/allergenic responses. In relation to the pharmacokinetic profile, S206C exhibited twofold higher activity than WT and P40S two hours after injection. In conclusion, we present bioengineered E. coli asparaginases with high specific enzyme activity and fewer side effects.

Kinetics characterization of a low immunogenic recombinant l-asparaginase from Phaseolus vulgaris with cytotoxic activity against leukemia cells

l-asparaginases play a crucial role in the treatment of acute lymphoblastic leukemia (ALL), a type of cancer that mostly affects children and teenagers. However, it is common for these molecules to cause adverse reactions during treatment. These downsides ignite the search for novel asparaginases to mitigate these problems. Thus, this work aimed to produce and characterize a recombinant asparaginase from Phaseolus vulgaris (Asp-P). In this study, Asp-P was expressed in Escherichia coli with high yields and optimum activity at 40 °C, pH 9.0. The enzyme Km and Vmax values were 7.05 mM and 1027 U/mg, respectively. Asp-P is specific for l-asparagine, showing no activity against l-glutamine and other amino acids. The enzyme showed a higher cytotoxic effect against Raji than K562 cell lines, but only at high concentrations. In silico analysis indicated that Asp-P has lower immunogenicity than a commercial enzyme. Asp-P induced biofilm formation by Candida sp. due to sublethal dose, showing an underexplored potential of asparaginases. The absence of glutaminase activity, lower immunogenicity and optimal activity similar to physiological temperature conditions are characteristics that indicate Asp-P as a potential new commercial enzyme in the treatment of ALL and its underexplored application in the treatment of other diseases.

Expression, characterization and cytotoxicity of recombinant l-asparaginase II from Salmonella paratyphi cloned in Escherichia coli

L-asparaginase is a remarkable antineoplastic enzyme used in medicine for the treatment of acute lymphoblastic leukemia (ALL) as well as in food industries. In this work, the L-asparaginase-II gene from Salmonella paratyphi was codon-optimized, cloned, and expressed in E. coli as a His-tag fusion protein. Then, using a two-step chromatographic procedure it was purified to homogeneity as confirmed by SDS-PAGE, which also showed its monomeric molecular weight to be 37 kDa. This recombinant L-asparaginase II from Salmonella paratyphi (recSalA) was optimally active at pH 7.0 and 40 °C temperature. It was highly specific for L-asparagine as a substrate, while its glutaminase activity was low. The specific activity was found to be 197 U/mg and the kinetics elements Km, Vmax, and kcat were determined to be 21 mM, 28 μM/min, and 39.6 S-1, respectively. Thermal stability was assessed using a spectrofluorometer and showed Tm value of 45 °C. The in-vitro effects of recombinant asparaginase on three different human cancerous cell lines (MCF7, A549 and Hep-2) by MTT assay showed remarkable anti-proliferative activity. Moreover, recSalA exhibited significant morphological changes in cancer cells and IC50 values ranged from 28 to 45.5 μg/ml for tested cell lines. To investigate the binding mechanism of SalA, both substrates L-asparagine and l-glutamine were docked with the protein and the binding energy was calculated to be -4.2 kcal mol-1 and - 4.4 kcal mol-1, respectively. In summary, recSalA has significant efficacy as an anticancer agent with potential implications in oncology while its in-vivo validation needs further investigation.

Development of a bioengineered Erwinia chrysanthemi asparaginase to enhance its anti-solid tumor potential for treating gastric cancer

Asparaginase has been traditionally applied for only treating acute lymphoblastic leukemia due to its ability to deplete asparagine. However, its ultimate anticancer potential for treating solid tumors has not yet been unleashed. In this study, we bioengineered Erwinia chrysanthemi asparaginase (ErWT), one of the US Food and Drug Administration-approved types of amino acid depleting enzymes, to achieve double amino acid depletions for treating a solid tumor. We constructed a fusion protein by joining an albumin binding domain (ABD) to ErWT via a linker (GGGGS)5 to achieve ABD-ErS5. The ABD could bind to serum albumin to form an albumin-ABD-ErS5 complex, which could avoid renal clearance and escape from anti-drug antibodies, resulting in a remarkably prolonged elimination half-life of ABD-ErS5. Meanwhile, ABD-ErS5 did not only deplete asparagine but also glutamine for ∼2 weeks. A biweekly administration of ABD-ErS5 (1.5 mg/kg) significantly suppressed tumor growth in an MKN-45 gastric cancer xenograft model, demonstrating a novel approach for treating solid tumor depleting asparagine and glutamine. Multiple administrations of ABD-ErS5 did not cause any noticeable histopathological abnormalities of key organs, suggesting the absence of acute toxicity to mice. Our results suggest ABD-ErS5 is a potential therapeutic candidate for treating gastric cancer.

Reverse Phase Proteomic Array Profiling of Asparagine Synthetase Expression in Newly Diagnosed Acute Myeloid Leukemia

Asparaginase-based therapy is a cornerstone in acute lymphoblastic leukemia (ALL) treatment, capitalizing on the methylation status of the asparagine synthetase (ASNS) gene, which renders ALL cells reliant on extracellular asparagine. Contrastingly, ASNS expression in acute myeloid leukemia (AML) has not been thoroughly investigated, despite studies suggesting that AML with chromosome 7/7q deletions might have reduced ASNS levels. Here, we leverage reverse phase protein arrays to measure ASNS expression in 810 AML patients and assess its impact on outcomes. We find that AML with inv(16) has the lowest overall ASNS expression. While AML with deletion 7/7q had ASNS levels slightly lower than those of AML without deletion 7/7q, this observation was not significant. Low ASNS expression correlated with improved overall survival (46 versus 54 weeks, respectively, p = 0.011), whereas higher ASNS levels were associated with better response to venetoclax-based therapy. Protein correlation analysis demonstrated association between ASNS and proteins involved in methylation and DNA repair. In conclusion, while ASNS expression was not lower in patients with deletion 7/7q as initially predicted, ASNS levels were highly variable across AML patients. Further studies are needed to assess whether patients with low ASNS expression are susceptible to asparaginase-based therapy due to their inability to augment compensatory ASNS expression upon asparagine depletion.

Asparaginase II of Saccharomyces cerevisiae. Characterization of the ASP3 gene

Purified preparations of asparaginase II of Saccharomyces cerevisiae exhibit two protein bands upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cloning and sequencing of the ASP3 gene, and partial amino acid sequencing as asparaginase II, imply that both bands are encoded by ASP3 but have different N termini. Northern blot analysis using the cloned ASP3 gene as a probe indicates that nitrogen catabolite repression of asparaginase II is achieved by alteration in mRNA levels. Deletion of sequences greater than 600 base pairs upstream from the initiation AUG codon results in an altered response to certain nitrogen sources in strains containing the truncated gene.

L-asparaginase-driven antibiosis in Pseudomonas fluorescens EK007: A promising biocontrol strategy against fire blight

Fire blight, caused by Erwinia amylovora, is a destructive bacterial disease affecting pear and apple trees. The biocontrol ability of Pseudomonas fluorescens EK007 suppresses E. amylovora through competitive exclusion. In this study, EK007 was isolated from the pear phylloplane and characterized as an effective biological agent through antibacterial compounds. To identify the mechanisms underlying EK007's biocontrol activity, physiological tests, transposon insertion mutant libraries, allelic exchange, and whole-genome sequencing were performed. A transposon mutation in the massC homolog gene, part of the massetolide A lipopeptide biosynthesis cluster, reduced the biocontrol efficiency. Allelic exchange confirmed cyclic lipopeptide (CLP) as part of the mechanism. Additionally, a gacA mutant isolated by transposon mutagenesis showed deficient inhibition activity. Culture conditions and nutritional sources clearly influenced EK007's antimicrobial activity against E. amylovora. Growth yield generally correlated with antibiotic production, with amino acids and iron affecting production. Asparagine and aspartate shut down biocontrol activity. This study presents preliminary findings on a novel CLP that may contribute to EK007's antibacterial activity against E. amylovora. While EK007 shows promise as a biocontrol candidate compared to related strains, these results are based solely on in vitro studies, highlighting the need for further investigations to evaluate its efficacy in natural environments.