Recent research progress on microbial l-asparaginases

Identification and Thermostability Modification of the Mesophilic L-asparaginase from Limosilactobacillus secaliphilus

L-asparaginase (L-ASNase, E.C.3.5.1.1) could effectively inhibit the formation of acrylamide (AA) by hydrolyzing the AA precursor L-asparagine. However, most of the L-ASNases showed a relatively weak thermostability, posing a big threat on the application of enzyme at high processing temperatures. Here, the recombinant L-ASNase from mesophilic bacteria Limosilactobacillus secaliphilus was identified for the first time. The recombinant enzyme exhibited its optimal activity at pH 8.0 and 60 ℃. Additionally, the thermostability of L. secaliphilus L-ASNase was enhanced by site-directed mutagenesis after multiple sequence alignment. Ten mutants were reasonably constructed, among which the single-point mutants L24Y, S55T, and V155S showed more than 1 ℃ elevated Tm value compared to the wild-type enzyme. In addition, the half-life of mutant at 40, 50, and 55 ℃ was 376.7 min, 62.1 min, and 18.7 min, much higher than that of wild-type enzyme. The molecular dynamic simulation showed that compared to the wild-type enzyme, the structural stability of V155S was greatly strengthened due to the lower RMSF and RMSD value as well as a decreased total energy compared to that of the wild-type enzyme. The results were positive and provided some useful information for the thermostability modification of L-ASNase.

Application of sequential design for enhanced L-asparaginase synthesis from Ganoderma australe GPC191

With an increasing demand for L-asparaginase in pharmaceutical and food sectors for its cytostatic and acrylamide-reducing qualities, there's a need to discover novel, highly productive enzyme sources with improved pharmacokinetic profiles. Keeping this in mind, the present study aimed at maximizing the potential of Ganoderma australe GPC191 to produce L-asparaginase by fermentation medium optimization using statistical validation. Of the 11 physicochemical parameters evaluated under submerged fermentation conditions through one-factor-at-a-time approach and Plackett-Burman design, only four parameters (inoculum load, L-asparagine, soybean meal, and initial pH) influenced L-asparaginase production, significantly (p < 0.001). The optimal levels and interaction effects of these on the overall production were further evaluated by the central composite rotatable design of response surface methodology. Post-optimization, 27.34 U/mL was predicted as the maximum activity at pH 7 with 5n inoculum load and 15 g/L each of L-asparagine and soybean meal. Experimental validation yielded an activity of 28.52 U/mL, indicating an overall 18.17-fold increase from the unoptimized stage. To our knowledge, this is the first report signifying the L-asparaginase production aptitude of G. australe with sequential statistical validation using agricultural waste, which can serve as a model to enhance its yields, offering a sustainable and cost-effective solution for industrial application.

Characterization and applications of glutaminase free L-asparaginase from indigenous Bacillus halotolerans ASN9

L-asparaginase (L-ASNase) is a versatile anticancer and acrylamide reduction enzyme predominantly used in medical and food industries. However, the high specificity of L-asparaginase formulations for glutamine, low thermostability, and blood clearance are the major disadvantages. Present study describes production, characterization, and applications of glutaminase free extracellular L-asparaginase from indigenous Bacillus halotolerans ASN9 isolated from soil sample. L-asparaginase production was optimized in M9 medium (containing 0.2% sucrose and 1% L-asparagine) that yielded maximum L-ASNase with a specific activity of 256 U mg-1 at pH 6 and 37°C. L-asparaginase was purified through acetone precipitation and Sephadex G-100 column, yielding 48.9 and 24% recovery, respectively. Enzyme kinetics revealed a Vmax of 466 mM min-1 and Km of 0.097 mM. Purified L-ASNase showed no activity against glutamine. The purified glutaminase free L-ASNase has a molecular mass of 60 kDa and an optimum specific activity of 3083 U mg-1 at pH 7 and 37°C. The enzyme retains its activity and stability over a wide range of pH and temperature, in the presence of selected protein inhibitors (SDS, β-mercaptoethanol), CoCl2, KCl, and NaCl. The enzyme also exhibited antioxidant activity against DPPH radical (IC50 value 70.7 μg mL-1) and anticancer activity against U87 human malignant glioma (IC50 55 μg mL-1) and Huh7 human hepatocellular carcinoma (IC50 37 μg mL-1) cell lines. Normal human embryonic kidney cells (HEK293) had greater than 80% cell viability with purified L-ASNase indicating its least cytotoxicity against normal cells. The present work identified potent glutaminase free L-ASNase from B. halotolerans ASN9 that performs well in a wide range of environmental conditions indicating its suitability for various commercial applications.

Enzyme Engineering Strategies for the Bioenhancement of L-Asparaginase Used as a Biopharmaceutical

Over the past few years, there has been a surge in the industrial production of recombinant enzymes from microorganisms due to their catalytic characteristics being highly efficient, selective, and biocompatible. L-asparaginase (L-ASNase) is an enzyme belonging to the class of amidohydrolases that catalyzes the hydrolysis of L-asparagine into L-aspartic acid and ammonia. It has been widely investigated as a biologic agent for its antineoplastic properties in treating acute lymphoblastic leukemia. The demand for L-ASNase is mainly met by the production of recombinant type II L-ASNase from Escherichia coli and Erwinia chrysanthemi. However, the presence of immunogenic proteins in L-ASNase sourced from prokaryotes has been known to result in adverse reactions in patients undergoing treatment. As a result, efforts are being made to explore strategies that can help mitigate the immunogenicity of the drug. This review gives an overview of recent biotechnological breakthroughs in enzyme engineering techniques and technologies used to improve anti-leukemic L-ASNase, taking into account the pharmacological importance of L-ASNase.

Characterization of a Type II L-Asparaginase from the Halotolerant Bacillus subtilis CH11

L-asparaginases from bacterial sources have been used in antineoplastic treatments and the food industry. A type II L-asparaginase encoded by the N-truncated gene ansZP21 of halotolerant Bacillus subtilis CH11 isolated from Chilca salterns in Peru was expressed using a heterologous system in Escherichia coli BL21 (DE3)pLysS. The recombinant protein was purified using one-step nickel affinity chromatography and exhibited an activity of 234.38 U mg-1 and a maximum catalytic activity at pH 9.0 and 60 °C. The enzyme showed a homotetrameric form with an estimated molecular weight of 155 kDa through gel filtration chromatography. The enzyme half-life at 60 °C was 3 h 48 min, and L-asparaginase retained 50% of its initial activity for 24 h at 37 °C. The activity was considerably enhanced by KCl, CaCl2, MgCl2, mercaptoethanol, and DL-dithiothreitol (p-value < 0.01). Moreover, the Vmax and Km were 145.2 µmol mL-1 min-1 and 4.75 mM, respectively. These findings evidence a promising novel type II L-asparaginase for future industrial applications.

Characterization of L-asparaginase from Streptomyces koyangensis SK4 with acrylamide-minimizing potential in potato chips

Microbial L-asparaginase is well known for its application in food industries to reduce acrylamide content in fried starchy food. L-asparaginase produced by Arctic actinomycetes Streptomyces koyangensis SK4 was purified and studied for biochemical characterization. The L-asparaginase was purified with a yield of 15.49% and final specific activity of 179.77 IU/mg of protein. The enzyme exhibited a molecular weight of 43 kDa. The optimum pH and temperature for maximum activity of the purified enzyme were 8.5 °C and 40 °C, respectively. The enzyme expressed maximum activity at an incubation period of 30 min and a substrate concentration of 0.06 M. The enzyme has a low Km value of 0.041 M and excellent substrate specificity toward L-asparagine. The enzyme activity was inhibited by metal ions Ba2+ and Hg2+, while Mn2+ and Mg2+ enhanced the activity. The study evaluated the acrylamide reduction potential of L-asparaginase from Streptomyces koyangensis SK4 in potato chips. The blanching plus L-asparaginase treatment of potato slices resulted in a 50% reduction in acrylamide content. The study illustrated an effective acrylamide reduction strategy in potato chips using L-asparaginase from a psychrophilic actinomycete. Besides the acrylamide reduction potential, L-asparaginase from Streptomyces koyangensis SK4 also did not exhibit any glutaminase or urease activity which is an outstanding feature of L-asparaginase to be used as a chemotherapeutic agent.

Anticancer Asparaginases: Perspectives in Using Filamentous Fungi as Cell Factories

The enzyme L-asparaginase (L-asparagine amidohydrolase) catalyzes the breakdown of L-asparagine into aspartate and ammonia, which leads to an anti-neoplastic activity stemming from its capacity to deplete L-asparagine concentrations in the bloodstream, and it is therefore used in cases of acute lymphoblastic leukemia (ALL) to inhibit malignant cell growth. Nowadays, this anti-cancer enzyme, largely produced by Escherichia coli, is well established on the market. However, E. coli L-asparaginase therapy has side effects such as anaphylaxis, coagulation abnormality, low plasma half-life, hepatotoxicity, pancreatitis, protease action, hyperglycemia, and cerebral dysfunction. This review provides a perspective on the use of filamentous fungi as alternative cell factories for L-asparaginase production. Filamentous fungi, such as various Aspergillus species, have superior protein secretion capacity compared to yeast and bacteria and studies show their potential for the future production of proteins with humanized N-linked glycans. This article explores the past and present applications of this important enzyme and discusses the prospects for using filamentous fungi to produce safe eukaryotic asparaginases with high production yields.

Insights into the Distribution and Functional Properties of l-Asparaginase in the Archaeal Domain and Characterization of Picrophilus torridus Asparaginase Belonging to the Novel Family Asp2like1

l-Asparaginase catalyzes the hydrolysis of l-asparagine to aspartic acid and ammonia and is used in the medical and food industries. In this investigation, from the proteomes of 176 archaeal organisms (with completely sequenced genomes), 116 homologs of l-asparaginase were obtained from 86 archaeal organisms segregated into Asp1, Asp2, IaaA, Asp2like1, and Asp2like2 families based on the conserved domain. The similarities and differences in the structure of selected representatives from each family are discussed. From the two novel archaeal l-asparaginase families Asp2like1 and Asp2like2, a representative of Asp2like1 family Picrophilus torridus asparaginase (PtAsp2like1) was characterized in detail to find its suitability in therapeutics. PtAsp2like1 was a glutaminase-free asparaginase that showed the optimum activity at 80 °C and pH 10.0. The Km of PtAsp2like1 toward substrate l-asparagine was 11.69 mM. This study demonstrates the improved mapping of asparaginases in the archaeal domain, facilitating future focused research on archaeal asparaginases for therapeutic applications.

Bioprocessing and purification of extracellular L-asparaginase produced by endophytic Colletotrichum gloeosporioides and its anticancer activity

L-asparaginase is an enzyme commonly used to treat acute lymphoblastic leukemia. Commercialized bacterial L-asparaginase has been reported to cause several life-threatening complications during treatment, hence the need to seek alternative sources of L-asparaginase. In this study, the novelty of upstream and downstream bioprocessing of L-asparaginase from a fungal endophyte, Colletotrichum gloeosporioides, and the cytotoxicity evaluation was demonstrated. Six variables (carbon source and concentration, nitrogen source and concentration, incubation period, temperature, pH and agitation rate) known to influence L-asparaginase production were studied using One-Factor-At-A-Time (OFAT) approach, with four significant variables further optimized using Response Surface Methodology (RSM). The crude extract produced using optimized condition was purified, characterized and examined for its anticancer effect. Purification of fungal L-asparaginase was performed via ultrafiltration and size exclusion chromatography, which are less common techniques. The protein profile and monomeric weight of L-asparaginase were determined using SDS-PAGE and Western blot. Cytotoxicity of purified L-asparaginase on leukemic Jurkat E6 and oral carcinoma cells were studied using MTS assay for 24 h and 48 h. OFAT results from optimization showed that glucose and L-asparagine concentrations, incubation period and temperature, were significant factors affecting L-asparaginase production by C. gloeosporioides. RSM analysis further evidence the significant interaction between glucose and L-asparagine concentrations in inducing L-asparaginase production. Purified L-asparaginase was profiled with specific activity of 255.02 IU/mg protein, purification fold of 6.12, and 34.63% of enzyme recovery. SDS and Western blot revealed that the purified L-asparaginase might be a tetramer with monomeric units of 25 kDa. Purified L-asparaginase was discovered to be more efficient against Jurkat leukemic cells than against H103 oral carcinoma cells, as lower IC₅₀ value was observed for Jurkat cell lines (46 .36 ± 1.52 µg/mL for Jurkat and 125.56 ± 7.28 µg/mL for H103). In short, purified L-asparaginase derived from endophytic C. gloeosporioides showed high purity and significant anticancer effect toward cancer cells. This study therefore demonstrated the potential of fungal L-asparaginase as alternative chemotherapy drug in the future.

Regulation of l- and d-Aspartate Transport and Metabolism in Acinetobacter baylyi ADP1

The regulated uptake and consumption of d-amino acids by bacteria remain largely unexplored, despite the physiological importance of these compounds. Unlike other characterized bacteria, such as Escherichia coli, which utilizes only l-Asp, Acinetobacter baylyi ADP1 can consume both d-Asp and l-Asp as the sole carbon or nitrogen source. As described here, two LysR-type transcriptional regulators (LTTRs), DarR and AalR, control d- and l-Asp metabolism in strain ADP1. Heterologous expression of A. baylyi proteins enabled E. coli to use d-Asp as the carbon source when either of two transporters (AspT or AspY) and a racemase (RacD) were coexpressed. A third transporter, designated AspS, was also discovered to transport Asp in ADP1. DarR and/or AalR controlled the transcription of aspT, aspY, racD, and aspA (which encodes aspartate ammonia lyase). Conserved residues in the N-terminal DNA-binding domains of both regulators likely enable them to recognize the same DNA consensus sequence (ATGC-N₇-GCAT) in several operator-promoter regions. In strains lacking AalR, suppressor mutations revealed a role for the ClpAP protease in Asp metabolism. In the absence of the ClpA component of this protease, DarR can compensate for the loss of AalR. ADP1 consumed l- and d-Asn and l-Glu, but not d-Glu, as the sole carbon or nitrogen source using interrelated pathways. IMPORTANCE A regulatory scheme was revealed in which AalR responds to l-Asp and DarR responds to d-Asp, a molecule with critical signaling functions in many organisms. The RacD-mediated interconversion of these isomers causes overlap in transcriptional control in A. baylyi. Our studies improve understanding of transport and regulation and lay the foundation for determining how regulators distinguish l- and d-enantiomers. These studies are relevant for biotechnology applications, and they highlight the importance of d-amino acids as natural bacterial growth substrates.

Structural Aspects of E. coli Type II Asparaginase in Complex with Its Secondary Product L-Glutamate

Bacterial L-asparaginases are amidohydrolases (EC 3.5.1.1) capable of deaminating L-asparagine and, with reduced efficiency, L-glutamine. Interest in the study of L-asparaginases is driven by their use as biodrugs for the treatment of acute lymphoblastic leukemia. Here, we report for the first time the description of the molecular structure of type II asparaginase from Escherichia coli in complex with its secondary product, L-glutamate. To obtain high-quality crystals, we took advantage of the N24S variant, which has structural and functional features similar to the wild-type enzyme, but improved stability, and which yields more ordered crystals. Analysis of the structure of the N24S-L-glutamate complex (N24S-GLU) and comparison with its apo and L-aspartate-bound form confirmed that the enzyme-reduced catalytic efficiency in the presence of L-glutamine is due to L-glutamine misfitting into the enzyme-binding pocket, which causes a local change in the catalytic center geometry. Moreover, a tight interaction between the two protomers that form the enzyme active site limits the capability of L-glutamine to fit into (and to exit from) the binding pocket of E. coli L-asparaginase, explaining why the enzyme has lower glutaminolytic activity compared to other enzymes of the same family, in particular the Erwinia chrysanthemi one.

Purification and anticancer activity of glutaminase and urease free intracellular l-asparaginase from Chaetomium sp

l-asparaginase is a chemotherapeutic drug used in the treatment of acute lymphoblastic leukemia, a malignant disorder in children. l-asparaginase helps in removing acrylamide found in fried and baked foods which is carcinogenic in nature. The search for new therapeutic enzymes is of great interest in both medical and food applications. The present work aims to isolate the intracellular l-asparaginase from endophytic fungi Chaetomium sp. The intracellular enzyme was partially purified by chromatographic techniques. Molecular weight of enzyme was found to be ~66 kDa by SDS PAGE analysis. The enzyme is highly specific for l-asparagine and did not show glutaminase and urease activity. Maximum enzyme activity was found to be 58 ± 5 U/mL at 40 °C, pH 7.0 with 2 μg of protein. Intracellular l-asparaginase from Chaetomium sp. exhibited anticancer activity on human blood cancer (MOLT-4) cells.

Microbial L-asparaginase for Application in Acrylamide Mitigation from Food: Current Research Status and Future Perspectives

L-asparaginase (E.C.3.5.1.1) hydrolyzes L-asparagine to L-aspartic acid and ammonia, which has been widely applied in the pharmaceutical and food industries. Microbes have advantages for L-asparaginase production, and there are several commercially available forms of L-asparaginase, all of which are derived from microbes. Generally, L-asparaginase has an optimum pH range of 5.0-9.0 and an optimum temperature of between 30 and 60 °C. However, the optimum temperature of L-asparaginase from hyperthermophilic archaea is considerable higher (between 85 and 100 °C). The native properties of the enzymes can be enhanced by using immobilization techniques. The stability and recyclability of immobilized enzymes makes them more suitable for food applications. This current work describes the classification, catalytic mechanism, production, purification, and immobilization of microbial L-asparaginase, focusing on its application as an effective reducer of acrylamide in fried potato products, bakery products, and coffee. This highlights the prospects of cost-effective L-asparaginase, thermostable L-asparaginase, and immobilized L-asparaginase as good candidates for food application in the future.

Microbial production, molecular modification, and practical application of l-Asparaginase: A review

L-Asparaginase (L-ASNase, EC 3.5.1.1), an antitumor drug for acute lymphoblastic leukemia (ALL) therapy, is widely used in the clinical field. Similarly, L-ASNase is also a powerful and significant biological tool in the food industry to inhibit acrylamide (AA) formation. This review comprehensively summarizes the latest achievements and improvements in the production, modification, and application of microbial L-ASNase. To date, the expression levels and optimization of expression hosts such as Escherichia coli, Bacillus subtilis, and Pichia pastoris, have made significant progress. In addition, examples of successful modification of L-ASNase such as decreasing glutaminase activity, increasing the in vivo stability, and enhancing thermostability have been presented. Impressively, the application of L-ASNase as a food addition aid, as well as its commercialization in the pharmaceutical field, and cutting-edge biosensor application developments have been summarized. The presented results and proposed ideas could be a good guide for other L-ASNase researchers in both scientific and practical fields.

L-asparaginase from Aspergillus oryzae spp.: effects of production process and biochemical parameters

L-asparaginases prevent the formation of acrylamide, a substance commonly found in foods subjected to heat and that also contains reducing sugars and L-asparagine. This work aimed to select a strain of Aspergillus spp. able to produce L-asparaginase and to optimize the fermentation parameters, the partial purification and biochemical characterization were also performed. The Aspergillus oryzae IOC 3999 was selected due to its greater enzymatic activity: 1443.57 U/mL of L-asparaginase after 48 h of fermentation. The optimized conditions allowed for an increase of 223% on the L-asparaginase production: 2.9% lactose, 2.9% L-asparagine and 0.7% hydrolyzed casein, 0.152% KH₂PO₄, 0.052% KCl and MgSO₄, 0.001% of CuNO₃.3H₂O, ZnSO₄.7H₂O and FeSO₄.7H₂O adjusted to pH 7.0; added a concentration of 5.05x10⁶ spores/mL at 30 °C for 100 rpm. A purification factor of 2.11 was found and the molecular mass was estimated at 20.8 kDa. The enzyme showed optimum activity at 60 °C and pH 5 and stability at 50 °C for 1 h. The enzyme presented desirable biochemical characteristics, mainly the acid pH stability, indicating that the enzyme would work well in food matrices due to the closeness of pH, meaning that it could be a potential option for use in the food industry.

Non-classical secretion of a type I L-asparaginase in Bacillus subtilis

L-asparaginase (EC 3.5.1.1) showed great commercial value owing to its effective treatment of acute lymphoblastic leukemia (ALL), lymphoid system malignancies and Hodgkin disease, and also to its use in the prevention of acrylamide formation in fried and baked foods. In this study, a type I L-asparaginase gene from Bacillus licheniformis Z-1 (BlAase) was cloned and expressed in Bacillus subtilis RIK 1285. Results showed that even without the mediation of any N-terminal signal peptides, BlAase can efficiently secrete into the medium. Further investigation indicated that the secretion of the BlAase was via neither Sec- nor Tat-dependent secretion pathway, and both the N- and C-terminal regions of the BlAase were essential for its expression and secretion, implying that BlAase might be secreted via a non-classical secretion pathway. To explore its secretion ability, BlAase was used as a signal peptide to direct the secretion of various heterologous proteins, where two of five proteins were successfully secreted with the mediation of BlAase. To the best of our knowledge, this is the first time to achieve extracellular expression of L-asparaginase via non-classical protein secretion pathway in B. subtilis, and provide a potential tool for secretion of recombinant proteins expressed in B. subtilis using BlAase as a signal peptide.

Characterization of Penicillium crustosum L-asparaginase and its acrylamide alleviation efficiency in roasted coffee beans at non-cytotoxic levels

This work aims at isolating a fungal source for L-asparaginase production to be applied in reducing acrylamide levels in coffee beans at non-cytotoxic levels. An L-asparaginase-producing fungus was isolated from an agricultural soil sample and identified as Penicillium crustosum NMKA 511. A maximum L-asparaginase activity of 19.10 U/mL was obtained by the above-mentioned fungus when grown under optimum conditions (i.e. 16.96 g/L sucrose as carbon source, 1.92 g/L peptone as nitrogen source, pH 7.7 and 33.5 °C). Further, the produced L-asparaginase was purified and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that P. crustosum L-asparaginase was a heterodimer enzyme with molecular weights of approximately 41.3 and 44.4 kDa. Also, the purified P. crustosum L-asparaginase was specific towards L-asparagine and showed negligible and no effects towards L-glutamine and D-asparagine, respectively. Additionally, the purified L-asparaginase reduced the acrylamide levels by 80.7% and 75.8% in light and dark roasted coffee beans, respectively. The amount of L-asparaginase used to reduce acrylamide was considered safe when cell viability reached 94.6%.

Recent Strategies and Applications for l-Asparaginase Confinement

l-asparaginase (ASNase, EC 3.5.1.1) is an aminohydrolase enzyme with important uses in the therapeutic/pharmaceutical and food industries. Its main applications are as an anticancer drug, mostly for acute lymphoblastic leukaemia (ALL) treatment, and in acrylamide reduction when starch-rich foods are cooked at temperatures above 100 °C. Its use as a biosensor for asparagine in both industries has also been reported. However, there are certain challenges associated with ASNase applications. Depending on the ASNase source, the major challenges of its pharmaceutical application are the hypersensitivity reactions that it causes in ALL patients and its short half-life and fast plasma clearance in the blood system by native proteases. In addition, ASNase is generally unstable and it is a thermolabile enzyme, which also hinders its application in the food sector. These drawbacks have been overcome by the ASNase confinement in different (nano)materials through distinct techniques, such as physical adsorption, covalent attachment and entrapment. Overall, this review describes the most recent strategies reported for ASNase confinement in numerous (nano)materials, highlighting its improved properties, especially specificity, half-life enhancement and thermal and operational stability improvement, allowing its reuse, increased proteolysis resistance and immunogenicity elimination. The most recent applications of confined ASNase in nanomaterials are reviewed for the first time, simultaneously providing prospects in the described fields of application.

Interactive effects of asparagine and aspartate homeostasis with sex and age for the risk of type 2 diabetes risk

BACKGROUND

Asparagine and aspartate homeostasis are linked with type 2 diabetes (T2D). This study aimed to explore whether asparagine and aspartate metabolism interacted with sex and age to increase the risk of T2D.

METHODS

From 27 May 2015 to 3 August 2016, we consecutively retrieved 1032 T2D patients and 1522 subjects without T2D from a tertiary care hospital in Liaoning, China. Restricted cubic spline nested in the logistic regression was used to draw odds ratio curves of plasma asparagine to aspartate ratio for T2D by sex and age. Cut-off point was selected where curves went apart, indicating possible interaction. Addictive interactions of asparagine to aspartate ratio with sex or age and secondary interaction with copresence of unfavorable sex and age were further estimated using relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), and synergy index (S).

RESULTS

Ratio of asparagine to aspartate > 1.5 was associated with elevated risk of T2D (OR 7.99, 95%CI 5.50 to 11.6), which was enhanced by female gender to 13.6, (95%CI 8.10-22.9) and by > 50 years of age to 28.7 (14.6-56.3), with significant additive interactions. There was a significant secondary-interaction of copresence of female sex and > 50 years of age with high asparagine to aspartate ratio for increased T2D risk with the OR being further increased to 34.4 (20.5-57.5).

CONCLUSIONS

High asparagine to aspartate ratio was associated with markedly increased risk of T2D, which was further amplified by either female gender or > 50 years of age, and especially both.

Studies on efficient production of a novel l-asparaginase by a newly isolated Pseudomonas resinovorans IGS-131 and its heterologous expression in Escherichia coli

In the current study, the production of novel glutaminase free l-asparaginase from a new microbial source (Pseudomonas resinovorans IGS-131) is reported. Optimization of l-asparaginase production using conventional and statistical optimization techniques resulted in an enzyme yield of 37.63 IU/mL, which was 3.45-fold higher than the initial enzyme activity (i.e., 10.91 IU/mL). l-Asparaginase production from P. resinovorans IGS-131 was successfully carried out at the bioreactor level and investigations on the effect of agitation rates showed a maximum asparaginase yield of 38.88 IU/mL after 24 h fermentation at 400 rpm. The l-asparaginase gene from this source, showing 78% identity with a reported sequence in GenBank, was expressed in Escherichia coli rosetta DE3. The molecular weight of the recombinant protein was determined as 35.6 kDa. Downstream processing of recombinant l-asparaginase resulted in a purified protein concentration of 62.53 mg/L, which showed good free radical scavenging activity of 62%. The current findings provide promising results for a process of l-asparaginase production from P. resinovorans IGS-131. Furthermore, the recombinant production of this enzyme could help in avoiding the complexity of down streaming processes associated with the purification of this enzyme from wild-type organisms.

Development and characterization of a novel l-asparaginase/MWCNT nanobioconjugate

The enzyme l-asparaginase (ASNase) presents effective antineoplastic properties used for acute lymphoblastic leukemia treatment besides their potential use in the food sector to decrease the acrylamide formation. Considering their applications, the improvement of this enzyme's properties by efficient immobilization techniques is in high demand. Carbon nanotubes are promising enzyme immobilization supports, since these materials have increased surface area and effective capacity for enzyme loading. Accordingly, in this study, multi-walled carbon nanotubes (MWCNTs) were explored as novel supports for ASNase immobilization by a simple adsorption method. The effect of pH and contact time of immobilization, as well as the ASNase to nanoparticles mass ratio, were optimized according to the enzyme immobilization yield and relative recovered activity. The enzyme–MWCNTs bioconjugation was confirmed by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Raman and transmission electron microscopy (TEM) studies. MWCNTs have a high ASNase loading capacity, with a maximum immobilization yield of 90%. The adsorbed ASNase retains 90% of the initial enzyme activity at the optimized conditions (pH 8.0, 60 min, and 1.5 × 10⁻³ g mL⁻¹ of ASNase). According to these results, ASNase immobilized onto MWCNTs can find improved applications in several areas, namely biosensors, medicine and food industry.

l-Asparaginase immobilization by adsorption over MWCNTs for potential application in pharmaceutical and food industries.

l-Asparaginase from Aspergillus spp.: production based on kinetics, thermal stability and biochemical characterization

This study describes the production of native l-asparaginases by submerged fermentation from Aspergillus strains and provides the biochemical characterization, kinetic and thermodynamic parameters of the three ones that stood out for high l-asparaginase production. For comparison, the commercial fungal l-asparaginase was also studied. Both commercial and l-asparaginase from Aspergillus oryzae CCT 3940 showed optimum activity and stability in the pH range from 5 to 8 and the asparaginase from Aspergillus niger LBA 02 was stable in a more alkaline pH range. About the kinetic parameters, the denaturation constant increased with the heating temperature for all l-asparaginases, indicating that the l-asparaginase activity decreased at higher temperatures, especially above 60 °C. Moreover, l-asparaginase from A. oryzae CCT 3940 remained stable after 60 min at 50 °C. None of the l-asparaginases were inhibited by high NaCl concentrations, which are highly desirable for food industry application. The catalytic activities of all the l-asparaginases were enhanced by the presence of Mn²⁺ and inhibited by p-chloromercuribenzoate and iodoacetamide. The l-asparaginase from the Aspergillus strains and the commercial enzyme had similar K _m when l-asparagine was used as substrate. None of the l-asparaginases, except the l-asparaginase from A. niger LBA 02, could hydrolyze the substrate l-glutamine, which is of interest for medical proposes, since the glutaminase activity is usually related to adverse reaction during the leukemia treatment. This study showed that these new three non-recombinant l-asparaginases studied have potential application in the food and pharmaceutical industries, especially due to their good thermostability.

Interferences that impact measuring optimal L-asparaginase activity and consequent errors interpreting these data

L-asparaginase is an enzyme produced by microorganisms, plants, and animals, which is used clinically for the treatment for acute lymphoblastic leukemia (ALL) and, in the food industry, to control acrylamide formation in baked foods. The purpose of this review was to evaluate the available literature regarding microbial sources of L-asparaginase, culture media used to achieve maximum enzyme expression in microbial fermentations, and assay methods employed to assess L-asparaginase activity. Studies were gathered by searching PubMed, and Web of Science databases before January 22, 2018, with no time restrictions. The articles were evaluated according to the source of L-asparaginase being studied, the nitrogen source in the culture medium, the type of sample, and the method employed to evaluate L-asparaginase activity. Bacterial L-asparaginase appeared to be the most commonly studied source of the enzyme and, most often, the enzyme activity was assayed from crude protein extracts using the Nessler method, which is an indirect measurement of asparaginase activity that determines the concentration of ammonia generated after the action of the enzyme on the substrate, L-asparagine. However, ammonia is also generated throughout microbial fermentations and this endogenous ammonia will also reduce the Nessler reagent if crude microbial extracts are used to determine total L-asparaginase activity. We suggest that current estimates of L-asparaginase activity reported in the literature may be overestimated when Nessler reagent is used, since we were unable to find a single study that made reference to the possible inference of fermentation derived ammonia.

Antitumor activity and ability to prevent acrylamide formation in fried foods of asparaginase from soybean root nodules

A novel asparaginase (designated srnASNase) has been purified from soybean root nodules and identified by MALDI-TOF/TOF-MS. And the enzymatic properties, antitumor activity and the ability to prevent acrylamide formation in fried foods of srnASNase were evaluated. SrnASNase had high specific activity (531.37 U/mg) toward L-asparagine under optimum conditions (pH 8.0 and 40°C), no activity toward L-glutamine and D-glutamine, but trace activity toward D-asparagine. It was stable in the pH range of 7.0-9.0 and up to 40°C. The Km and Vmax of srnASNase were 0.36 mM and 51.64 mM/min, respectively. Further, in vitro anti-proliferative activity on human cancer cells assay showed that srnASNase was superior to commercial asparaginase in solution by controlling the tumor cell growth with time. In addition, srnASNase showed more effective acrylamide mitigation than commercial asparaginase in fried foods. These results indicate that srnASNase is a potential candidate for applications in the food processing and pharmaceutical industry. PRACTICAL APPLICATIONS: L-asparaginase (L-asparagine amidohydrolase; EC 3.5.1.1) is an enzyme that catalyzes the hydrolysis of the amide group of the side-chain of L-asparagine into aspartic acid and ammonia. It has long been used as a primary component in the treatment of acute lymphoblastic leukemia (All) and other related blood cancers. Apart from its clinical usage, L-asparaginase has attracted more attention in the food processing industries as a promising acrylamide-mitigating agent in recent years. This research revealed that soybean root nodules might be good sources of novel asparaginase.

Development of L-Asparaginase Biobetters: Current Research Status and Review of the Desirable Quality Profiles

L-Asparaginase (ASNase) is a vital component of the first line treatment of acute lymphoblastic leukemia (ALL), an aggressive type of blood cancer expected to afflict over 53,000 people worldwide by 2020. More recently, ASNase has also been shown to have potential for preventing metastasis from solid tumors. The ASNase treatment is, however, characterized by a plethora of potential side effects, ranging from immune reactions to severe toxicity. Consequently, in accordance with Quality-by-Design (QbD) principles, ingenious new products tailored to minimize adverse reactions while increasing patient survival have been devised. In the following pages, the reader is invited for a brief discussion on the most recent developments in this field. Firstly, the review presents an outline of the recent improvements on the manufacturing and formulation processes, which can severely influence important aspects of the product quality profile, such as contamination, aggregation and enzymatic activity. Following, the most recent advances in protein engineering applied to the development of biobetter ASNases (i.e., with reduced glutaminase activity, proteolysis resistant and less immunogenic) using techniques such as site-directed mutagenesis, molecular dynamics, PEGylation, PASylation and bioconjugation are discussed. Afterwards, the attention is shifted toward nanomedicine including technologies such as encapsulation and immobilization, which aim at improving ASNase pharmacokinetics. Besides discussing the results of the most innovative and representative academic research, the review provides an overview of the products already available on the market or in the latest stages of development. With this, the review is intended to provide a solid background for the current product development and underpin the discussions on the target quality profile of future ASNase-based pharmaceuticals.

Enzymes in Metabolic Anticancer Therapy

Cancer treatment has greatly improved over the last 50 years, but it remains challenging in several cases. Useful therapeutic targets are normally unique peculiarities of cancer cells that distinguish them from normal cells and that can be tackled with appropriate drugs. It is now known that cell metabolism is rewired during tumorigenesis and metastasis as a consequence of oncogene activation and oncosuppressors inactivation, leading to a new cellular homeostasis typically directed towards anabolism. Because of these modifications, cells can become strongly or absolutely dependent on specific substrates, like sugars, lipids or amino acids. Cancer addictions are a relevant target for therapy, as removal of an essential substrate can lead to their selective cell-cycle arrest or even to cell death, leaving normal cells untouched. Enzymes can act as powerful agents in this respect, as demonstrated by asparaginase, which has been included in the treatment of Acute Lymphoblastic Leukemia for half a century. In this review, a short outline of cancer addictions will be provided, focusing on the main cancer amino acid dependencies described so far. Therapeutic enzymes which have been already experimented at the clinical level will be discussed, along with novel potential candidates that we propose as new promising molecules. The intrinsic limitations of their present molecular forms, along with molecular engineering solutions to explore, will also be presented.

Cloning and expression of L-asparaginase from Bacillus tequilensis PV9W and therapeutic efficacy of Solid Lipid Particle formulations against cancer

L-asparaginase, a therapeutic involved in cancer therapy, from Bacillus tequilensis PV9W (ansA gene) was cloned and over expressed in Escherichia coli BL21 (DE3), achieved the aim of maximizing the yield of the recombinant enzyme (6.02 ± 1.77 IU/mL) within 12 h. The native L-asparaginase of B. tequilensis PV9W was encapsulated using solid lipid particles by hot lipid emulsion method, which is reported for first time in this study. Subsequently, the lipid encapsulated L-asparaginase (LPE) was characterized by SEM, UV-Vis spectroscopy, FT-IR, SDS-PAGE and its thermo stability was also analyzed by TGA. Further characterization of LPE revealed that enzyme was highly stable for 25 days when stored at 25 °C, showed high pH (9) tolerance and longer trypsin half-life (120 min). In addition, the cytotoxic ability of LPE on HeLa cells was highly enhanced compared to the native L-asparaginase from Bacillus tequilensis PV9W. Moreover, better kinetic velocity and lower Km values of LPE aided to detect L-asparagine in cell extracts by Differential Pulse Voltammetry (DPV) method. The LPE preparation also showed least immunogenic reaction when tested on normal macrophage cell lines. This LPE preparation might thus pave way for efficient drug delivery and enhancing the stability of L-asparaginase for its therapeutic applications.

Simultaneous cell disruption and semi-quantitative activity assays for high-throughput screening of thermostable L-asparaginases

L-asparaginase, which catalyses the hydrolysis of L-asparagine to L-aspartate, has attracted the attention of researchers due to its expanded applications in medicine and the food industry. In this study, a novel thermostable L-asparaginase from Pyrococcus yayanosii CH1 was cloned and over-expressed in Bacillus subtilis 168. To obtain thermostable L-asparaginase mutants with higher activity, a robust high-throughput screening process was developed specifically for thermophilic enzymes. In this process, cell disruption and enzyme activity assays are simultaneously performed in 96-deep well plates. By combining error-prone PCR and screening, six brilliant positive variants and four key amino acid residue mutations were identified. Combined mutation of the four residues showed relatively high specific activity (3108 U/mg) that was 2.1 times greater than that of the wild-type enzyme. Fermentation with the mutant strain in a 5-L fermenter yielded L-asparaginase activity of 2168 U/mL.

A new pH indicator dye-based method for rapid and efficient screening of l-asparaginase producing microorganisms

l-asparaginase is a pharmaceutically and industrially important enzyme as it has potential to treat different cancers and inhibit acrylamide formation in fried and baked food products. In the present study, an attempt was made to screen for new and novel l-asparaginase producers using a widely applied phenol red and bromothymol blue (BTB)¹ dye-based plate assay. Screening of four different soil samples for l-asparaginase producers resulted in the isolation of three new potential l-asparaginase producing bacteria. These three strains identified (by 16S rRNA sequencing) as a Pseudomonas resinovorans strain IGS-131, a Bacillus safensis strain IGS-81, and a Glutamicibacter arilaitensis strain ICS-13 with enzyme activities of 10.91 IU/ml, 6.65 IU/ml, and 1.47 IU/ml, respectively. These three strains of bacteria have not been reported as l-asparaginase producers previously. Also, we developed a new pH indicator dye-based plate assay for the screening of l-asparaginase producers after testing eight different pH indicator dyes. This cresol red dye-based method gave a better differentiable zone of hydrolysis and consistent results as compared to previously reported phenol red and BTB-based plate assay. It was also found to be efficient in comparison to all other dyes studied. It produced a bright yellow color at acidic pH (5.5) and turned into a dark red or maroon color when pH was increased (above 7.5). This finding is expected to make screening of all kinds of l-asparaginases more comfortable, rapid, and efficient.

Expression and purification of L-asparaginase from Escherichia coli and the inhibitory effects of cyclic dipeptides

L-asparaginase, a key enzyme involved in nitrogen metabolism, is an effective anti-tumour agent. Cyclic dipeptides, a group of compounds, contain several important biological functions. In this paper, we proposed a novel method for L-asparaginase expression and purification from Echerichia coli and determined the effect of cyclic dipeptides on the enzymatic activity of recombinant L-asparaginase. The gene ansB encoding L-asparaginase was amplified from the genome of E. coli BL21 (DE3) by polymerase chain reaction and sub-cloned into pET-15b vector to construct expressing plasmid pET-15b-ansB. The expression of recombinant protein was purified by affinity chromatography using a nickel resin followed by anion exchange chromatography. The purity and quality of the recombinant L-asparaginase were optimised. The results indicated that km for the recombinant L-asparaginase was 3.02 × 10^-4 mol/L. Both cyclo-(Pro-Tyr) and cyclo-(Pro-Phe) could inhibit the activity of recombinant L-asparaginase at the level of 10^-5 mol/L.

Current applications and different approaches for microbial l-asparaginase production

l-asparaginase (EC 3.5.1.1) is an enzyme that catalysis mainly the asparagine hydrolysis in l-aspartic acid and ammonium. This enzyme is presented in different organisms, such as microorganisms, vegetal, and some animals, including certain rodent's serum, but not unveiled in humans. It can be used as important chemotherapeutic agent for the treatment of a variety of lymphoproliferative disorders and lymphomas (particularly acute lymphoblastic leukemia (ALL) and Hodgkin's lymphoma), and has been a pivotal agent in chemotherapy protocols from around 30 years. Also, other important application is in food industry, by using the properties of this enzyme to reduce acrylamide levels in commercial fried foods, maintaining their characteristics (color, flavor, texture, security, etc.) Actually, l-asparaginase catalyzes the hydrolysis of l-asparagine, not allowing the reaction of reducing sugars with this aminoacid for the generation of acrylamide. Currently, production of l-asparaginase is mainly based in biotechnological production by using some bacteria. However, industrial production also needs research work aiming to obtain better production yields, as well as novel process by applying different microorganisms to increase the range of applications of the produced enzyme. Within this context, this mini-review presents l-asparaginase applications, production by different microorganisms and some limitations, current investigations, as well as some challenges to be achieved for profitable industrial production.

Purification, Characterization and Comparison between Two New L-asparaginases from Bacillus PG03 and Bacillus PG04

BACKGROUND

L-asparaginase has been used as a chemotherapeutic agent in treatment of lymphoblastic leukemia. In the present investigation, Bacillus sp. PG03 and Bacillus sp. PG04 were studied.

METHODS

L- asparaginases were produced using different culture media and were purified using ion exchange chromatography.

RESULTS

Maximum productivity was obtained when asparagine was used as the nitrogen source at pH 7 and 48 h after cultivation. New intracellular L-asparaginases showed an apparent molecular weight of 25 kDa and 30 kDa by SDS-PAGE respectively. These enzymes were active in a wide pH range (3-9) with maximum activity at pH 6 for Bacillus PG03 and pH 7 for Bacillus PG04 L-asparaginase. Bacillus PG03 enzyme was optimally active at 37 ˚C and Bacillus PG04 maximum activity was observed at 40˚C. Kinetic parameters k_m and V_max of both enzymes were studied using L-asparagine as the substrate. Thermal inactivation studies of Bacillus PG03 and Bacillus PG04 L-asparaginase exhibited t_1/2 of 69.3 min and 34.6 min in 37 ˚C respectively. Also T₅₀ and ∆G of inactivation were measured for both enzymes.

CONCLUSION

The results revealed that both enzymes had appropriate characteristics and thus could be a potential candidate for medical applications.

Batch and fed-batch bioreactor studies for the enhanced production of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428

The effect of dissolved oxygen (DO) level and pH (controlled/uncontrolled) was first studied to enhance the production of novel glutaminase-free L-asparaginase by Pectobacterium carotovorum MTCC 1428 in a batch bioreactor. The optimum level of DO was found to be 20%. The production of L-asparaginase was found to be maximum when pH of the medium was maintained at 8.5 after 12 h of fermentation. Under these conditions, P. carotovorum produced 17.97 U/mL of L-asparaginase corresponding to the productivity of 1497.50 U/L/h. The production of L-asparaginase was studied in fed-batch bioreactor by feeding L-asparagine (essential substrate for production) and/or glucose (carbon source for growth) at the end of the reaction period of 12 h. The initial medium containing both L-asparagine and glucose in the batch mode and L-asparagine in the feeding stream was found to be the best combination for enhanced production of glutaminase-free L-asparaginase. Under this condition, the L-asparaginase production was increased to 38.8 U/mL, which corresponded to a productivity of 1615.8 U/L/h. The production and productivity were increased by 115.8% and 7.9%, respectively, both of which are higher than those obtained in the batch bioreactor experiments.

Acrylamide: inhibition of formation in processed food and mitigation of toxicity in cells, animals, and humans

Potentially toxic acrylamide is largely derived from the heat-inducing reactions between the amino group of the amino acid asparagine and carbonyl groups of glucose and fructose in plant-derived foods including cereals, coffees, almonds, olives, potatoes, and sweet potatoes. This review surveys and consolidates the following dietary aspects of acrylamide: distribution in food, exposure and consumption by diverse populations, reduction of the content in different food categories, and mitigation of adverse in vivo effects. Methods to reduce acrylamide levels include selecting commercial food with a low acrylamide content, selecting cereal and potato varieties with low levels of asparagine and reducing sugars, selecting processing conditions that minimize acrylamide formation, adding food-compatible compounds and plant extracts to food formulations before processing that inhibit acrylamide formation during processing of cereal products, coffees, teas, olives, almonds, and potato products, and reducing multiorgan toxicity (antifertility, carcinogenicity, neurotoxicity, teratogenicity). The herein described observations and recommendations are of scientific interest for food chemistry, pharmacology, and toxicology, but also have the potential to benefit nutrition, food safety, and human health.

Hemocompatible glutaminase free l-asparaginase from marine Bacillus tequilensis PV9W with anticancer potential modulating p53 expression

Glutaminase free l-asparaginase from a marine isolate Bacillus tequilensis PV9W: production, purification, characterization and its biological applications.