Recent Strategies and Applications for l-Asparaginase Confinement

Human Commensal Bacteria: Next-generation Pro- and Post-biotics for Anticancer Therapy

Cancer is a common, deadly disease with an unknown etiology. Meanwhile, current therapeutic options possess significant risks. However, probiotic bacteria and their metabolites have been reported to have antiproliferative and apoptotic effects on cancer cells. Therefore, because of their selective specificity and lack of treatment-associated comorbidities, these bacteria and their metabolites could be potential alternatives to conventional chemical and radiation therapies. Given their superior immunomodulatory and anti-cancer effects and lack of side effects, commensal bacteria derived from healthy humans are currently used as next-generation probiotics. This review summarizes current findings on these probiotic properties and anti-cancer activities of healthy human commensal bacteria. Additionally, the review focuses on small metabolites, proteins, and enzymes secreted by human commensal bacteria for their therapeutic applications against cancer. Further, utilizing a protein engineering strategy to reduce the toxicity of L-asparaginase, an enzyme-based anti-leukemia drug used for the last forty years, is also discussed. A possible workflow outline for isolating, identifying, screening, and characterizing human commensal bacterial strains for their therapeutic applications in cancer treatment is also proposed. This review emphasizes the need to explore various human commensal bacteria, not just mainstream lactic acid bacteria, for novel cancer therapeutics that provide multiple health benefits.

Recent advances in L-Asparaginase enzyme production and formulation development for acrylamide reduction during food processing

L-asparagine is an essential amino acid for cell growth and common constituent of all the proteins. During high temperature food processing it reacts with reducing sugars and leads to acrylamide production through a complex process known as Maillard reaction. L-asparaginase hydrolyses the amine-group of L-asparagine to produce aspartic acid and ammonia. L-asparaginase pre-treatment of potato led to more than 80 % reduction of acrylamide content in foods like french fries, potato chips and in flour-dough based products. New cost-effective strategies for large scale L-asparaginase production and diverse types of formulations will be needed to successfully integrate L-asparaginase in food processing. Here we comprehensively review the recent developments in enzyme production to enhance the yield, activity and specificity of L-asparaginase. Novel liquid and lyophilized formulations are developed to enhance stability and activity of the enzyme under different conditions. These developments present a promising approach to enzymatically mitigate acrylamide formation during food processing.

Isolation, Identification, and Characterization of L-asparaginase-Producing Human Commensal Bacterial Strains: A Promising Next-Gen Probiotics

L-asparaginase is an FDA-approved drug for treating blood cancer, but its inherent antigenicity and L-glutaminase activity are associated with hypersensitivity and organ toxicity. Extracellularly produced glutaminase-free L-asparaginase from human commensal bacteria may be a good alternative to reduce the side effects of therapeutic L-asparaginase. Here, we report the isolation and characterization of fourteen L-asparaginase-producing bacterial strains belonging to the genera Acinetobacter, Escherichia, Klebsiella, and Pseudomonas from human stool and saliva samples. To the best of our knowledge, this is the first report of L-asparaginase-producing human commensal bacterial strains isolated from healthy individuals. L-asparaginase produced by fecal and salivary isolates exhibited significantly higher activity (3.64 to 16.96 U/ml) toward L-asparagine than L-glutamine. Interestingly, L-asparaginase from fecal isolates, Escherichia coli strains 3F1 and 3F2 and salivary isolate Klebsiella pneumoniae 3S3, exhibited no L-glutaminase activity. These isolates were also sensitive to all tested antibiotics. Additionally, these three isolates demonstrated tolerance to pH 3.0 (≥ 88% survival) and 0.3% bile (≥ 95% survival), indicating their potential as probiotics. Among these isolates, L-asparaginase from the highest-producing K. pneumoniae 3S3 strain was found to be a homodimer, with native and subunit molecular weights of 110 kDa and 55 kDa, respectively. The purified enzyme can be further explored for its antitumor and immunomodulatory properties. Overall, future research can be expanded to include the use of a pool of human commensal bacteria as genuine and alternative sources of L-asparaginase for effective cancer treatments and cutting-edge next-generation probiotics.

Immobilization of L-Asparaginase on biofunctionalized magnetic graphene oxide nanocomposite: A promising approach for Enhanced Stability and reusability

The application of the amidohydrolase enzyme, L-asparaginase (ASNase), as a biocatalyst in the food and pharmaceutical industries has garnered significant interest. However, challenges such as hypersensitivity reactions, limited stability, and reusability under various operational conditions have hindered its cost-effective utilization. This paper introduces a novel nano-support for ASNase immobilization, namely the nanocomposite of iron oxide magnetic nanoparticles and amino acid-decorated graphene oxide (GO-Asp-Fe3O4). Characterization using FTIR spectroscopy, FE-SEM, and TEM microscopy revealed the homogeneous distribution of iron oxide nanoparticles on the surface of GO sheets. The effects of carrier functionalization and carrier-to-protein ratio on the immobilization of ASNase were studied to optimize the immobilization conditions. The magnetized nanocomposite of ASNase exhibited a 4.4-fold lower Michaelis-Menten constant (Km), suggesting an enhanced affinity for the substrate. The immobilized ASNase demonstrated two to eight times higher thermostability compared to the free enzyme and showed an extremely extended pH stability range. Furthermore, the immobilized enzyme retained over 80 % of its initial bioactivity after eight repeated reaction cycles. These findings suggest that the immobilization of ASNase on GO-Asp- Fe3O4 nanocomposite could be a viable option for industrial applications.

Targeted Polymeric Micelles System, Designed to Carry a Combined Cargo of L-Asparaginase and Doxorubicin, Shows Vast Improvement in Cytotoxic Efficacy

L-asparaginases (ASP) and Doxorubicin (Dox) are both used in the treatment of leukemia, including in combination. We have attempted to investigate if their combination within the same targeted delivery vehicle can make such therapy more efficacious. We assembled a micellar system, where the inner hydrophobic core was loaded with Dox, while ASP would absorb at the surface due to electrostatic interactions. To make such absorption stronger, we conjugated the ASP with oligoamines, such as spermine, and the lipid components of the micelle-lipoic and oleic acids-with heparin. When loaded with Dox alone, the system yielded about a 10-fold improvement in cytotoxicity, as compared to free Dox. ASP alone showed about a 2.5-fold increase in cytotoxicity, so, assuming additivity of the effect, one could expect a 25-fold improvement when the two agents are applied in combination. But in reality, a combination of ASP + Dox loaded into the delivery system produced a synergy, with a whopping 50× improvement vs. free individual component. Pharmacokinetic studies have shown prolonged circulation of micellar formulations in the bloodstream as well as an increase in the effective concentration of Dox in micellar form and a reduction in Dox accumulation to the liver and heart (which reduces hepatotoxicity and cardiotoxicity). For the same reason, Dox's liposomal formulation has been in use in the treatment of multiple types of cancer, almost replacing the free drug. We believe that an opportunity to deliver a combination of two types of drugs to the same target cell may represent a further step towards improvement in the risk-benefit ratio in cancer treatment.

Reducing Acrylamide Formation Potential by Targeting Free Asparagine Accumulation in Seeds

Acrylamide is a probable carcinogen in humans and is formed when reducing sugars react with free asparagine (Asn) during thermal processing of food. Although breeding for low reducing sugars worked well in potatoes, it is less successful in cereals. However, reducing free Asn in cereals has great potential for reducing acrylamide formation, despite the role that Asn plays in nitrogen transport and amino acid biosynthesis. In this perspective, we summarize the efforts aimed at reducing free Asn in cereal grains and discuss the potentials and challenges associated with targeting this essential amino acid, especially in a seed-specific manner.

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.

Assessment of structural behaviour of a new L-asparaginase and SAXS data-based evidence for catalytic activity in its monomeric form

The present study reports the structural and functional characterization of a new glutaminase-free recombinant L-asparaginase (PrASNase) from Pseudomonas resinovorans IGS-131. PrASNase showed substrate specificity to L-asparagine, and its kinetic parameters, Km, Vmax, and kcat were 9.49 × 10-3 M, 25.13 IUmL-1 min-1, and 3.01 × 103 s-1, respectively. The CD spectra showed that PrASNase consisted of 18.5 % helix, 21.5 % antiparallel sheets, 4.2 % parallel sheets, 14 % turns, and rest other structures. FTIR was used for the functional characterization, and molecular docking predicted that the substrate interacts with serine, alanine, and glutamine in the binding pocket of PrASNase. Differing from known asparaginases, structural characterization by small-angle X-ray scattering (SAXS) and analytical ultracentrifugation (AUC) unambiguously revealed PrASNase to exist as a monomer in solution at low temperatures and oligomerized to a higher state with temperature rise. Through SAXS studies and enzyme assay, PrASNase was found to be mostly monomer and catalytically active at 37 °C. Furthermore, this glutaminase-free PrASNase showed killing effects against WIL2-S and TF-1.28 cells with IC50 of 7.4 μg.mL-1 and 5.6 μg.mL-1, respectively. This is probably the first report with significant findings of fully active L-asparaginase in monomeric form using SAXS and AUC and demonstrated the potential of PrASNase in inhibiting cancerous cells, making it a potential therapeutic candidate.

Thermal Stability Enhancement of L-Asparaginase from Corynebacterium glutamicum Based on a Semi-Rational Design and Its Effect on Acrylamide Mitigation Capacity in Biscuits

Acrylamide is present in thermally processed foods, and it possesses toxic and carcinogenic properties. L-asparaginases could effectively regulate the formation of acrylamide at the source. However, current L-asparaginases have drawbacks such as poor thermal stability, low catalytic activity, and poor substrate specificity, thereby restricting their utility in the food industry. To address this issue, this study employed consensus design to predict the crucial residues influencing the thermal stability of Corynebacterium glutamicum L-asparaginase (CgASNase). Subsequently, a combination of site-point saturating mutation and combinatorial mutation techniques was applied to generate the double-mutant enzyme L42T/S213N. Remarkably, L42T/S213N displayed significantly enhanced thermal stability without a substantial impact on its enzymatic activity. Notably, its half-life at 40 °C reached an impressive 13.29 ± 0.91 min, surpassing that of CgASNase (3.24 ± 0.23 min). Moreover, the enhanced thermal stability of L42T/S213N can be attributed to an increased positive surface charge and a more symmetrical positive potential, as revealed by three-dimensional structural simulations and structure comparison analyses. To assess the impact of L42T/S213N on acrylamide removal in biscuits, the optimal treatment conditions for acrylamide removal were determined through a combination of one-way and orthogonal tests, with an enzyme dosage of 300 IU/kg flour, an enzyme reaction temperature of 40 °C, and an enzyme reaction time of 30 min. Under these conditions, compared to the control (464.74 ± 6.68 µg/kg), the acrylamide reduction in double-mutant-enzyme-treated biscuits was 85.31%, while the reduction in wild-type-treated biscuits was 68.78%. These results suggest that L42T/S213N is a promising candidate for industrial applications of L-asparaginase.

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.

Response surface methodology based optimized production, purification, and characterization of L-asparaginase from Fusarium foetens

L-asparaginase is used as one of the prime chemotherapeutic agents to treat acute lymphoblastic leukemia. L-asparaginase obtained from bacteria exhibits hypersensitive reactions including various side effects. The present work aimed to optimize growth parameters for maximum production of L-asparaginase by Fusarium foetens through response surface methodology, its purification, and characterization. The optimization of L-asparaginase production by Fusarium foetens was initially done through a one-factor-at-a-time method. L-asparaginase production was further optimized using a central composite design based response surface methodology. The maximum L-asparaginase activity of 12.83 IU/ml was obtained under the following growth conditions; temperature-27.5 °C, pH-8, inoculum concentration-1.5 × 10⁶ spores/ml, and incubation period-7 days. In comparison with the unoptimized growth conditions (4.58 IU/ml), the optimization led to a 2.65-fold increase in the L-asparaginase activity. The L-asparaginase from Fusarium foetens was purified 15.60-fold, with a yield of 39.89% using DEAE-cellulose column chromatography. After purification, the L-asparaginase activity was determined to be 127.26 IU/ml and the specific activity was found to be 231.38 IU/mg. The molecular mass was estimated to be approximately 37 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme showed optimum activity at pH 5, and a temperature of 40 °C. The enzyme showed 100% specificity towards L-asparagine and no activity towards L-glutamine. Its activity was enhanced by Mn²⁺, Fe²⁺, and Mg², while it was inhibited by β-mercaptoethanol and EDTA. The Km and Vmax of the purified L-asparaginase were found to be 23.82 mM and 210.3 IU/ml respectively. The results suggest that Fusarium foetens could be a potent candidate for the bioprocessing of L-asparaginase at a large scale.

Current state of molecular and metabolic strategies for the improvement of L-asparaginase expression in heterologous systems

Heterologous expression of L-asparaginase (L-ASNase) has become an important area of research due to its clinical and food industry applications. This review provides a comprehensive overview of the molecular and metabolic strategies that can be used to optimize the expression of L-ASNase in heterologous systems. This article describes various approaches that have been employed to increase enzyme production, including the use of molecular tools, strain engineering, and in silico optimization. The review article highlights the critical role that rational design plays in achieving successful heterologous expression and underscores the challenges of large-scale production of L-ASNase, such as inadequate protein folding and the metabolic burden on host cells. Improved gene expression is shown to be achievable through the optimization of codon usage, synthetic promoters, transcription and translation regulation, and host strain improvement, among others. Additionally, this review provides a deep understanding of the enzymatic properties of L-ASNase and how this knowledge has been employed to enhance its properties and production. Finally, future trends in L-ASNase production, including the integration of CRISPR and machine learning tools are discussed. This work serves as a valuable resource for researchers looking to design effective heterologous expression systems for L-ASNase production as well as for enzymes production in general.

L-Asparaginase delivery systems targeted to minimize its side-effects

L-asparaginase (L-ASP) is one of the key enzymes used in therapeutic applications, particularly to treat Acute Lymphocytic Leukemia (ALL). L-asparagine is a non-essential amino acid, which means that it can be synthesized by the body and is not required to be obtained through the diet. The synthesis of L-asparagine occurs primarily in the liver, but it also takes place in other tissues throughout the body. In contrast, leukemic cells cannot synthesize L-asparagine due the absence of L-asparagine synthetase and should obtain it from circulating sources for protein synthesis and cell division processes to ensure their vital functions. L-ASP catalyzes the deamination process of L-asparagine amino-acid into aspartic acid and ammonia, depriving leukemic cells of asparagine. This leads to decreased protein synthesis and cell division in tumor cells. However, using L-ASP has side effects, such as hypersensitivity or allergic reaction, antigenicity, short half-life, temporary blood clearance, and toxicity. L-ASP immobilization can minimize the side effects of L-ASP by stopping the immune system from attacking non-human enzymes and improving the enzyme's performance. The first strategy includes modification of enzyme structure, such as covalent binding (conjugation), adsorption to the support material and cross-linking of the enzyme. The chemical modification of residues, often nonspecific, changes the enzyme's hydrophobicity and surface charge, lowering the enzyme's activity. Also, the first strategy exposes the enzyme's surface to the environment. This eliminates its performance and does not allow targeted delivery of the enzyme. The second strategy is based on the entrapment of the enzyme inside the protecting structure or encapsulation. This strategy offers the same benefits as the first. Still, it also enables reducing toxicity, prolonging in vivo half-life, enhancing stability and activity, enables a targeted delivery and controlled release of the enzyme. Compared to the first strategy, encapsulation does not modify the chemical structure of the enzyme since L-ASP is only effective against leukemia in its native tetrameric form. This review aims to present state of the art in L-ASP formulations developed for reducing the side effects of L-ASP, focusing on describing improvements in their safety. The primary focus in the field remains to be improving the overall performance of the L-ASP formulations. Almost all encapsulation systems allow reducing immune response due to screening the enzyme from antibodies and prolonging its half-life. However, the enzyme's activity and stability depend on the encapsulation system type. Therefore, the selection of the right encapsulation system is crucial in therapy due to its effect on the performance parameters of the L-ASP. Biodegradable and biocompatible materials, such as chitosan, alginate and liposomes, mainly attract the researcher's interest in enzyme encapsulation. The research trends are also moving towards developing formulations with targeted delivery and increased selectivity.

The anticancer effect of PASylated calreticulin-targeting L-ASNase in solid tumor bearing mice with immunogenic cell death-inducing chemotherapy

L-Asparaginase (L-ASNase), a bacterial enzyme that degrades asparagine, has been commonly used in combination with several chemical drugs to treat malignant hematopoietic cancers such as acute lymphoblastic leukemia (ALL). In contrast, the enzyme was known to inhibit the growth of solid tumor cells in vitro, but not to be effective in vivo. We previously reported that two novel monobodies (CRT3 and CRT4) bound specifically with calreticulin (CRT) exposed on tumor cells and tissues during immunogenic cell death (ICD). Here, we engineered L-ASNases conjugated with monobodies at the N-termini and PAS200 tags at the C-termini (CRT3LP and CRT4LP). These proteins were expected to possess four monobody and PAS200 tag moieties, which did not disrupt the L-ASNase conformation. These proteins were expressed 3.8-fold more highly in E. coli than those without PASylation. The purified proteins were highly soluble, with much greater apparent molecular weights than expected ones. Their affinity (Kd) against CRT was about 2 nM, 4-fold higher than that of monobodies. Their enzyme activity (∼6.5 IU/nmol) was similar to that of L-ASNase (∼7.2 IU/nmol), and their thermal stability was significantly increased at 55 °C. Their half-life times were > 9 h in mouse sera, about 5-fold longer than that of L-ASNase (∼1.8 h). Moreover, CRT3LP and CRT4LP bound specifically with CRT exposed on tumor cells in vitro, and additively suppressed the tumor growth in CT-26 and MC-38 tumor-bearing mice treated with ICD-inducing drugs (doxorubicin and mitoxantrone) but not with a non-ICD-inducing drug (gemcitabine). All data indicated that PASylated CRT-targeted L-ASNases enhanced the anticancer efficacy of ICD-inducing chemotherapy. Taken together, L-ASNase would be a potential anticancer drug for treating solid tumors.

Biochemical characterization of extremozyme L-asparaginase from Pseudomonas sp. PCH199 for therapeutics

L-asparaginase (L-ASNase) from microbial sources is a commercially vital enzyme to treat acute lymphoblastic leukemia. However, the side effects associated with the commercial formulations of L-ASNases intrigued to explore for efficient and desired pharmacological enzymatic features. Here, we report the biochemical and cytotoxic evaluation of periplasmic L-ASNase of Pseudomonas sp. PCH199 isolated from the soil of Betula utilis, the Himalayan birch. L-ASNase production from wild-type PCH199 was enhanced by 2.2-fold using the Response Surface Methodology (RSM). Increased production of periplasmic L-ASNase was obtained using an optimized osmotic shock method followed by its purification. The purified L-ASNase was a monomer of 37.0 kDa with optimum activity at pH 8.5 and 60 ℃. It also showed thermostability retaining 100.0% (200 min) and 90.0% (70 min) of the activity at 37 and 50 ℃, respectively. The K_m and V_max values of the purified enzyme were 0.164 ± 0.009 mM and 54.78 ± 0.4 U/mg, respectively. L-ASNase was cytotoxic to the K562 blood cancer cell line (IC₅₀ value 0.309 U/mL) within 24 h resulting in apoptotic nuclear morphological changes as examined by DAPI staining. Therefore, the dynamic functionality in a wide range of pH and temperature and stability of PCH199 L-ASNase at 37 ℃ with cytotoxic potential proves to be pharmaceutically important for therapeutic application.

Thermo-L-Asparaginases: From the Role in the Viability of Thermophiles and Hyperthermophiles at High Temperatures to a Molecular Understanding of Their Thermoactivity and Thermostability

L-asparaginase (L-ASNase) is a vital enzyme with a broad range of applications in medicine, food industry, and diagnostics. Among various organisms expressing L-ASNases, thermophiles and hyperthermophiles produce enzymes with superior performances-stable and heat resistant thermo-ASNases. This review is an attempt to take a broader view on the thermo-ASNases. Here we discuss the position of thermo-ASNases in the large family of L-ASNases, their role in the heat-tolerance cellular system of thermophiles and hyperthermophiles, and molecular aspects of their thermoactivity and thermostability. Different types of thermo-ASNases exhibit specific L-asparaginase activity and additional secondary activities. All products of these enzymatic reactions are associated with diverse metabolic pathways and are important for mitigating heat stress. Thermo-ASNases are quite distinct from typical mesophilic L-ASNases based on structural properties, kinetic and activity profiles. Here we attempt to summarize the current understanding of the molecular mechanisms of thermo-ASNases' thermoactivity and thermostability, from amino acid composition to structural-functional relationships. Research of these enzymes has fundamental and biotechnological significance. Thermo-ASNases and their improved variants, cloned and expressed in mesophilic hosts, can form a large pool of enzymes with valuable characteristics for biotechnological application.

Elucidation of the Reaction Mechanism of Cavia porcellus l-Asparaginase: A QM/MM Study

The l-asparaginase (l-ASNase) enzyme catalyzes the conversion of the non-essential amino acid l-asparagine into l-aspartic acid and ammonia. Importantly, the l-ASNases are used as a key part of the treatment of acute lymphoblastic leukemia (ALL); however, despite their benefits, they trigger severe side effects because they have their origin in bacterial species (Escherichia coli and Erwinia chrysanthemi). Therefore, one way to solve these side effects is the use of l-ASNases with characteristics similar to those of bacterial types, but from different sources. In this sense, Cavia porcellus l-ASNase (CpA) of mammalian origin is a promising enzyme because it possesses similarities with bacterial species. In this work, the hydrolysis reaction for C. porcellus l-asparaginase was studied from an atomistic point of view. The QM/MM methodology was employed to describe the reaction, from which it was found that the conversion mechanism of l-asparagine into l-aspartic acid occurs in four steps. It was identified that the nucleophilic attack and release of the ammonia group is the rate-limiting step of the reaction. In this step, the nucleophile (Thr₁₉) attacks the substrate (ASN) leading to the formation of a covalent intermediate and release of the leaving group (ammonia). The calculated energy barrier is 18.9 kcal mol^-1, at the M06-2X+D3(0)/6-311+G(2d,2p)//CHARMM36 level of theory, which is in agreement with the kinetic data available in the literature, 15.9 kcal mol^-1 (derived from the k_cat value of 38.6 s^-1). These catalytic aspects will hopefully pave the way toward enhanced forms of CpA. Finally, our work emphasizes that computational calculations may enhance the rational design of mutations to improve the catalytic properties of the CpA enzyme.

Post-refolding stability considerations for optimization of in-vitro refolding: L-asparaginase as a case study

BACKGROUND

L-Asparaginase is an essential enzyme for the food and biopharmaceutical industry. The stability, however, of L-asparaginase is widely known to be an issue. Commercial manufacturing of any biopharmaceutical involves hold-ups during processing, and can result in product loss if stability is an issue, as is the case with L-asparaginase. This interplay of product intermediate stability and process design is the focus of this investigation.

METHODS AND RESULTS

In this study, we propose a strategy to simultaneously increase the refolding yield and stability of refolded L-asparaginase so as to improve overall process yield. Using one variable at a time (OVAT) experiments, urea (6 M), solubilized inclusion bodies (15 mg/ml), refolding method (step dilution), and pH (8.6) were identified as significant process parameters. A design of experiment (DOE)-based optimization was then performed for the refolding step. The net outcome was more than a three-fold increase in enzyme recovery (i.e., 4.90 IU/ml) compared to unoptimized conditions (i.e., 1.26 IU/ml). Further, the L-asparaginase process intermediate was found to be stable for more than a week at room temperature and 2-8°C, while the unoptimized sample was stable at 2-8°C but did not show any activity at room temperature after 72 h.

CONCLUSIONS

The current study elucidates how process intermediate stability needs to be given due consideration during process optimization, particularly for products such as L-asparaginase which are labile.

Thermostability Improvement of L-Asparaginase from Acinetobacter soli via Consensus-Designed Cysteine Residue Substitution

To extend the application range of L-asparaginase in food pre-processing, the thermostability improvement of the enzyme is essential. Herein, two non-conserved cysteine residues with easily oxidized free sulfhydryl groups, Cys8 and Cys283, of Acinetobacter soli L-asparaginase (AsA) were screened out via consensus design. After saturation mutagenesis and combinatorial mutation, the mutant C8Y/C283Q with highly improved thermostability was obtained with a half-life of 361.6 min at 40 °C, an over 34-fold increase compared with that of the wild-type. Its melting temperature (T_m) value reaches 62.3 °C, which is 7.1 °C higher than that of the wild-type. Molecular dynamics simulation and structure analysis revealed the formation of new hydrogen bonds of Gln283 and the aromatic interaction of Tyr8 formed with adjacent residues, resulting in enhanced thermostability. The improvement in the thermostability of L-asparaginase could efficiently enhance its effect on acrylamide inhibition; the contents of acrylamide in potato chips were efficiently reduced by 86.50% after a mutant C8Y/C283Q treatment, which was significantly higher than the 59.05% reduction after the AsA wild-type treatment. In addition, the investigation of the mechanism behind the enhanced thermostability of AsA could further direct the modification of L-asparaginases for expanding their clinical and industrial applications.

Enhancing the Catalytic Activity of Type II L-Asparaginase from Bacillus licheniformis through Semi-Rational Design

Low catalytic activity is a key factor limiting the widespread application of type II L-asparaginase (ASNase) in the food and pharmaceutical industries. In this study, smart libraries were constructed by semi-rational design to improve the catalytic activity of type II ASNase from Bacillus licheniformis. Mutants with greatly enhanced catalytic efficiency were screened by saturation mutations and combinatorial mutations. A quintuple mutant ILRAC was ultimately obtained with specific activity of 841.62 IU/mg and kcat/Km of 537.15 min−1·mM−1, which were 4.24-fold and 6.32-fold more than those of wild-type ASNase. The highest specific activity and kcat/Km were firstly reported in type II ASNase from Bacillus licheniformis. Additionally, enhanced pH stability and superior thermostability were both achieved in mutant ILRAC. Meanwhile, structural alignment and molecular dynamic simulation demonstrated that high structure stability and strong substrate binding were beneficial for the improved thermal stability and enzymatic activity of mutant ILRAC. This is the first time that enzymatic activity of type II ASNase from Bacillus licheniformis has been enhanced by the semi-rational approach, and results provide new insights into enzymatic modification of L-asparaginase for industrial applications.

Molecular Mimicry of the Rheumatoid Arthritis-Related Immunodominant T-Cell Epitope within Type II Collagen (CII260-270) by the Bacterial L-Asparaginase

The etiology of most autoimmune diseases, including rheumatoid arthritis (RA), remains unclear. Both genetic and environmental factors are believed to be involved in pathogenesis. Molecular mimicry is considered one of the mechanisms for the occurrence of autoimmune diseases. The aim of the study was to determine whether the bacterial peptide L-ASNase67-81, which mimics the immunodominant T-cell epitope CII259-273, can induce T-cell reactivity in blood samples from RA patients and healthy subjects through molecular mimicry. Using bioinformatic molecular modeling methods, we first determined whether the L-ASNase67-81 peptide binds to the HLA-DRB1*04:01 molecule and whether the formed MHCII–peptide complex interacts with the corresponding T-cell receptor. To validate the obtained results, leukocytes isolated from early RA patients and healthy individuals were stimulated in vitro with L-ASNase67-81 and CII259-273 peptides as well as with bacterial L-asparaginase or human type II collagen (huCII). The activated T cells (CD4+CD154+) were analyzed by flow cytometry (FACS), and the levels of cytokines produced (IL-2, IL-17A/F, and IFN-γ) were measured by ELISA. Our in silico analyses showed that the bacterial peptide L-ASNase67-81 binds better to HLA-DRB1*04:01 compared to the immunodominant T-cell epitope CII259-273, mimicking its structure and localization in the binding groove of MHCII. Six contact points were involved in the molecular interaction of the peptide with the TCR. FACS data showed that after in vitro stimulation with the L-ASNase67-81 peptide, the percentage of activated T cells (CD154⁺CD4⁺) was significantly increased in both cell cultures isolated from ERA patients and those isolated from healthy individuals, as higher values were observed for the ERA group (9.92 ± 0.23 vs. 4.82 ± 0.22). Furthermore, the ELISA assays revealed that after stimulation with L-ASNase67-81, a significant increase in the production of the cytokines IL-2, IL-17A/F, and IFN-γ was detected in the group of ERA patients. Our data showed that the bacterial L-ASNase67-81 peptide can mimic the immunodominant T-cell epitope CII259-273 and activate HLA-DRB1*04:01-restricted T cells as well as induce cytokine production in cells isolated from ERA patients. These results are the first to demonstrate that a specific bacterial antigen could play a role in the pathogenesis of RA, mimicking the immunodominant T-cell epitope from type II collagen.

Advances in the application of immobilized enzyme for the remediation of hazardous pollutant: A review

Nowadays, ecofriendly, low-cost, and sustainable alternatives techniques have been focused on the effective removal of hazardous pollutants from the water streams. In this context, enzyme immobilization seems to be of specific interest to several researchers to develop novel, effective, greener, and hybrid strategies for the removal of toxic contaminants. Immobilization is a biotechnological tool, anchoring the enzymes on support material to enhance the stability and retain the structural conformation of enzymes for catalysis. Recyclability and reusability are the main merits of immobilized enzymes over free enzymes. Studies showed that immobilized enzyme laccase can be used up to 7 cycles with 66% efficiency, peroxidase can be recycled to 2 cycles with 50% efficiency, and also cellulase to 3 cycles with 91% efficiency. In this review, basic concepts of immobilization, different immobilization techniques, and carriers used for immobilization are summarized. In addition to that, the potential of immobilized enzymes as the bioremediation agents for the effective degradation of pollutants from the contaminated zone and the impact of different operating parameters are summarized in-depth. Further, this review provides future trends and challenges that have to be solved shortly for enhancing the potential of immobilized systems for large-scale industrial wastewater treatment.

Biochemical and Biological Evaluation of an L-Asparaginase from Isolated Escherichia coli MF-107 as an Anti-Tumor Enzyme on MCF7 Cell Line

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Advances on Delivery of Cytotoxic Enzymes as Anticancer Agents

Cancer is one of the most serious human diseases, causing millions of deaths worldwide annually, and, therefore, it is one of the most investigated research disciplines. Developing efficient anticancer tools includes studying the effects of different natural enzymes of plant and microbial origin on tumor cells. The development of various smart delivery systems based on enzyme drugs has been conducted for more than two decades. Some of these delivery systems have been developed to the point that they have reached clinical stages, and a few have even found application in selected cancer treatments. Various biological, chemical, and physical approaches have been utilized to enhance their efficiencies by improving their delivery and targeting. In this paper, we review advanced delivery systems for enzyme drugs for use in cancer therapy. Their structure-based functions, mechanisms of action, fused forms with other peptides in terms of targeting and penetration, and other main results from in vivo and clinical studies of these advanced delivery systems are highlighted.

Cis-Element Engineering Promotes the Expression of Bacillus subtilis Type I L-Asparaginase and Its Application in Food

Type I L-asparaginase from Bacillus licheniformis Z-1 (BlAase) was efficiently produced and secreted in Bacillus subtilis RIK 1285, but its low yield made it unsuitable for industrial use. Thus, a combined method was used in this study to boost BlAase synthesis in B. subtilis. First, fifteen single strong promoters were chosen to replace the original promoter P43, with PyvyD achieving the greatest BlAase activity (436.28 U/mL). Second, dual-promoter systems were built using four promoters (PyvyD, P43, PaprE, and PspoVG) with relatively high BlAase expression levels to boost BlAase output, with the engine of promoter PaprE-PyvyD reaching 502.11 U/mL. The activity of BlAase was also increased (568.59 U/mL) by modifying key portions of the PaprE-PyvyD promoter. Third, when the ribosome binding site (RBS) sequence of promoter PyvyD was replaced, BlAase activity reached 790.1 U/mL, which was 2.27 times greater than the original promoter P43 strain. After 36 h of cultivation, the BlAase expression level in a 10 L fermenter reached 2163.09 U/mL, which was 6.2 times greater than the initial strain using promoter P43. Moreover, the application potential of BlAase on acrylamide migration in potato chips was evaluated. Results showed that 89.50% of acrylamide in fried potato chips could be removed when combined with blanching and BlAase treatment. These findings revealed that combining transcription and translation techniques are effective strategies to boost recombinant protein output, and BlAase can be a great candidate for controlling acrylamide in food processing.

Production of a Novel Marine Pseudomonas aeruginosa Recombinant L-Asparaginase: Insight on the Structure and Biochemical Characterization

The present study focused on the cloning, expression, and characterization of L-asparaginase of marine Pseudomonas aeruginosa HR03 isolated from fish intestine. Thus, a gene fragment containing the L-asparaginase sequence of Pseudomonas aeruginosa HR03 isolated from the fish intestine was cloned in the pET21a vector and then expressed in Escherichia coli BL21 (DE3) cells. Thereafter, the recombinant L-asparaginase (HR03Asnase) was purified by nickel affinity chromatography, and the enzymatic properties of HR03Asnase, including the effects of pH and temperature on HR03Asnase activity and its kinetic parameters, were determined. The recombinant enzyme HR03Asnase showed the highest similarity to type I L-asparaginase from Pseudomonas aeruginosa. The three-dimensional (3D) modeling results indicate that HR03Asnase exists as a homotetramer. Its molecular weight was 35 kDa, and the maximum activity of the purified enzyme was observed at pH8 and at 40 °C. The k_m and V_max of the enzyme obtained with L-asparagine as substrate were 10.904 mM and 3.44 × 10^-2 mM/min, respectively. The maximum activity of HR03Asnase was reduced by 50% at 90 °C after 10-min incubation; however, the enzyme maintained more than 20% of its activity after 30-min incubation. This enzyme also maintained almost 50% of its activity at pH 12 after 40-min incubation. The evaluation of pH and temperature stability of HR03Asnase showed that the enzyme has a wide range of activity, which is a suitable characteristic for its application in different industries. Overall, the results of the present study indicate that marine sources are promising biological reservoirs for enzymes to be used for biotechnological purposes, and marine thermostable HR03Asnase is likely a potential candidate for its future usage in the pharmaceutical and food industries.

Immobilization and Characterization of L-Asparaginase over Carbon Xerogels

L-asparaginase (ASNase) is an aminohydrolase currently used in the pharmaceutical and food industries. Enzyme immobilization is an exciting option for both applications, allowing for a more straightforward recovery and increased stability. High surface area and customizable porosity make carbon xerogels (CXs) promising materials for ASNase immobilization. This work describes the influence of contact time, pH, and ASNase concentration on the immobilization yield (IY) and relative recovered activity (RRA) using the Central Composite Design methodology. The most promising results were obtained using CX with an average pore size of 4 nm (CX-4), reaching IY and RRA of 100%. At the optimal conditions (contact time 49 min, pH 6.73, and [ASNase] 0.26 mg·mL⁻¹), the ASNase-CXs biocomposite was characterized and evaluated in terms of kinetic properties and operational, thermal, and pH stabilities. The immobilized ASNase onto CX-4 retained 71% of its original activity after six continuous reaction cycles, showed good thermal stability at 37 °C (RRA of 91% after 90 min), and was able to adapt to both acidic and alkaline environments. Finally, the results indicated a 3.9-fold increase in the immobilized ASNase affinity for the substrate, confirming the potential of CXs as a support for ASNase and as a cost-effective tool for subsequent use in the therapeutic and food sectors.

[Mechanisms of development of side effects and drug resistance to asparaginase and ways to overcome them]

Asparaginase is one of the most important chemotherapeutic agents against acute lymphoblastic leukemia, the most common form of blood cancer. To date, both asparaginases from E. coli and Dickeya dadantii (formerly known as Erwinia chrysanthemi), used in hematology, induce chemoresistance in cancer cells and side effects in the form of hypersensitivity of immune reactions. Leukemic cells may be resistant to asparaginase due to the increased activity of asparagine synthetase and other mechanisms associated with resistance to asparaginase. Therefore, the search for new sources of L-asparaginases with improved pharmacological properties remains a promising and prospective study. This article discusses the mechanisms of development of resistance and drug resistance to L-asparaginase, as well as possible ways to overcome them.

Overview of the structure, side effects, and activity assays of l-asparaginase as a therapy drug of acute lymphoblastic leukemia

l-Asparaginase (l-ASNase is the abbreviation, l-asparagine aminohydrolase, E.C.3.5.1.1) is an enzyme that is clinically employed as an antitumor agent for the treatment of acute lymphoblastic leukemia (ALL). Although l-ASNase is known to deplete l-asparagine (l-Asn), causing cytotoxicity in leukemia cells, the specific molecular signaling pathways are not well defined. Because of the deficiencies in the production and administration of current formulations, the l-ASNase agent in clinical use is still associated with serious side effects, so controlling its dose and activity monitoring during therapy is crucial for improving the treatment success rate. Accordingly, it is urgent to summarize and develop effective analytical methods to detect l-ASNase activity in treatment. However, current reports on these detection methods are fragmented and also have not been systematically summarized and classified, thereby not only delaying the investigations of specific molecular mechanisms, but also hindering the development of novel detection methods. Herein, in this review, we provided a detailed summary of the l-ASNase structures, antitumor mechanism and side effects, and current detection approaches, such as fluorescence assays, colorimetric assays, spectroscopic assays and some other assays. All of them possess unique advantages and disadvantages, so it has been difficult to establish clear criteria for clinical application. We hope that this review will be of some value in promoting the development of l-ASNase activity detection methods.

Enhanced Enzyme Reuse through the Bioconjugation of L-Asparaginase and Silica-Based Supported Ionic Liquid-like Phase Materials

L-asparaginase (ASNase) is an amidohydrolase that can be used as a biopharmaceutical, as an agent for acrylamide reduction, and as an active molecule for L-asparagine detection. However, its free form displays some limitations, such as the enzyme's single use and low stability. Hence, immobilization is one of the most effective tools for enzyme recovery and reuse. Silica is a promising material due to its low-cost, biological compatibility, and tunable physicochemical characteristics if properly functionalized. Ionic liquids (ILs) are designer compounds that allow the tailoring of their physicochemical properties for a given task. If properly designed, bioconjugates combine the features of the selected ILs with those of the support used, enabling the simple recovery and reuse of the enzyme. In this work, silica-based supported ionic liquid-like phase (SSILLP) materials with quaternary ammoniums and chloride as the counterion were studied as novel supports for ASNase immobilization since it has been reported that ammonium ILs have beneficial effects on enzyme stability. SSILLP materials were characterized by elemental analysis and zeta potential. The immobilization process was studied and the pH effect, enzyme/support ratio, and contact time were optimized regarding the ASNase enzymatic activity. ASNase-SSILLP bioconjugates were characterized by ATR-FTIR. The bioconjugates displayed promising potential since [Si][N3444]Cl, [Si][N3666]Cl, and [Si][N3888]Cl recovered more than 92% of the initial ASNase activity under the optimized immobilization conditions (pH 8, 6 × 10-3 mg of ASNase per mg of SSILLP material, and 60 min). The ASNase-SSILLP bioconjugates showed more enhanced enzyme reuse than reported for other materials and immobilization methods, allowing five cycles of reaction while keeping more than 75% of the initial immobilized ASNase activity. According to molecular docking studies, the main interactions established between ASNase and SSILLP materials correspond to hydrophobic interactions. Overall, it is here demonstrated that SSILLP materials are efficient supports for ASNase, paving the way for their use in the pharmaceutical and food industries.

Highly Active Thermophilic L-Asparaginase from Melioribacter roseus Represents a Novel Large Group of Type II Bacterial L-Asparaginases from Chlorobi-Ignavibacteriae-Bacteroidetes Clade

L-asparaginase (L-ASNase) is a biotechnologically relevant enzyme for the pharmaceutical, biosensor and food industries. Efforts to discover new promising L-ASNases for different fields of biotechnology have turned this group of enzymes into a growing family with amazing diversity. Here, we report that thermophile Melioribacter roseus from Ignavibacteriae of the Bacteroidetes/Chlorobi group possesses two L-ASNases-bacterial type II (MrAII) and plant-type (MrAIII). The current study is focused on a novel L-ASNase MrAII that was expressed in Escherichia coli, purified and characterized. The enzyme is optimally active at 70 °C and pH 9.3, with a high L-asparaginase activity of 1530 U/mg and L-glutaminase activity ~19% of the activity compared with L-asparagine. The kinetic parameters KM and Vmax for the enzyme were 1.4 mM and 5573 µM/min, respectively. The change in MrAII activity was not significant in the presence of 10 mM Ni2+, Mg2+ or EDTA, but increased with the addition of Cu2+ and Ca2+ by 56% and 77%, respectively, and was completely inhibited by Zn2+, Fe3+ or urea solutions 2-8 M. MrAII displays differential cytotoxic activity: cancer cell lines K562, Jurkat, LnCap, and SCOV-3 were more sensitive to MrAII treatment, compared with normal cells. MrAII represents the first described enzyme of a large group of uncharacterized counterparts from the Chlorobi-Ignavibacteriae-Bacteroidetes clade.

Expanding the bio-catalysis scope and applied perspectives of nanocarrier immobilized asparaginases

l-asparaginase is an essential enzyme in medicine and a well-known chemotherapeutic agent. This enzyme's importance is not limited to its use as an anti-cancer agent; it also has a wide variety of medicinal applications. Antimicrobial properties, prevention of infectious disorders, autoimmune diseases, and canine and feline cancer are among the applications. Apart from the healthcare industry, its importance has been identified in the food industry as a food manufacturing agent to lower acrylamide levels. When isolated from their natural habitats, they are especially susceptible to different denaturing conditions due to their protein composition. The use of an immobilization technique is one of the most common approaches suggested to address these limitations. Immobilization is a technique that involves fixing enzymes to or inside stable supports, resulting in a heterogeneous immobilized enzyme framework. Strong support structures usually stabilize the enzymes' configuration, and their functions are maintained as a result. In recent years, there has been a lot of curiosity and focus on the ability of immobilized enzymes. The nanomaterials with ideal properties can be used to immobilize enzymes to regulate key factors that determine the efficacy of bio-catalysis. With applications in biotechnology, immunosensing, biomedicine, and nanotechnology sectors have opened a realm of opportunities for enzyme immobilization.

Technological Prospecting: Mapping Patents on L-asparaginases from Extremophilic Microorganisms

BACKGROUND

L-asparaginase (L-ASNase, L-asparagine amidohydrolase, E.C.3.5.1.1) is an enzyme with wide therapeutic applicability. Currently, the commercialized L-ASNase comes from mesophilic organisms, presenting low specificity to the substrate and limitations regarding thermostability and active pH range. Such factors prevent the maximum performance of the enzyme in different applications. Therefore, extremophilic organisms may represent important candidates for obtaining amidohydrolases with particular characteristics desired by the biotechnological market.

OBJECTIVES

The present study aims to carry out a technological prospecting of patents related to the L-asparaginases derived from extremophilic organisms, contributing to pave the way for further rational investigation and application of such enzymes.

METHODS

This patent literature review used six patents databases: The LENS, WIPO, EPO, USPTO, Patent Inspiration, and INPI.

RESULTS

It was analyzed 2860 patents, and 14 were selected according to combinations of descriptors and study criteria. Approximately 57.14% of the patents refer to enzymes obtained from archaea, especially from the speciesPyrococcus yayanosii (35.71% of the totality).

CONCLUSION

The present prospective study has singular relevance since there are no recent patent reviews for L-asparaginases, especially produced by extremophilic microorganisms. Although such enzymes have well-defined applications, corroborated by the patents compiled in this review, the most recent studies allude to new uses, such as the treatment of infections. The characterization of the catalytic profiles allows us to infer that there are potential sources still unexplored. Hence, the search for new L-ASNases with different characteristics will continue to grow in the coming years and, possibly, ramifications of the technological routes will be witnessed.

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.

Structural and biophysical aspects of l-asparaginases: a growing family with amazing diversity

l-Asparaginases have remained an intriguing research topic since their discovery ∼120 years ago, especially after their introduction in the 1960s as very efficient antileukemic drugs. In addition to bacterial asparaginases, which are still used to treat childhood leukemia, enzymes of plant and mammalian origin are now also known. They have all been structurally characterized by crystallography, in some cases at outstanding resolution. The structural data have also shed light on the mechanistic details of these deceptively simple enzymes. Yet, despite all this progress, no better therapeutic agents have been found to beat bacterial asparaginases. However, a new option might arise with the discovery of yet another type of asparaginase, those from symbiotic nitrogen-fixing Rhizobia, and with progress in the protein engineering of enzymes with desired properties. This review surveys the field of structural biology of l-asparaginases, focusing on the mechanistic aspects of the well established types and speculating about the potential of the new members of this amazingly diversified family.

L-asparaginase production review: bioprocess design and biochemical characteristics

In the past decades, the production of biopharmaceuticals has gained high interest due to its great sensitivity, specificity, and lower risk of negative effects to patients. Biopharmaceuticals are mostly therapeutic recombinant proteins produced through biotechnological processes. In this context, L-asparaginase (L-asparagine amidohydrolase, L-ASNase (E.C. 3.5.1.1)) is a therapeutic enzyme that has been abundantly studied by researchers due to its antineoplastic properties. As a biopharmaceutical, L-ASNase has been used in the treatment of acute lymphoblastic leukemia (ALL), acute myeloblastic leukemia (AML), and other lymphoid malignancies, in combination with other drugs. Besides its application as a biopharmaceutical, this enzyme is widely used in food processing industries as an acrylamide mitigation agent and as a biosensor for the detection of L-asparagine in physiological fluids at nano-levels. The great demand for L-ASNase is supplied by recombinant enzymes from Escherichia coli and Erwinia chrysanthemi. However, production processes are associated to low yields and proteins associated to immunogenicity problems, which leads to the search for a better enzyme source. Considering the L-ASNase pharmacological and food importance, this review provides an overview of the current biotechnological developments in L-ASNase production and biochemical characterization aiming to improve the knowledge about its production. KEY POINTS: • Microbial enzyme applications as biopharmaceutical and in food industry • Biosynthesis process: from the microorganism to bioreactor technology • Enzyme activity and kinetic properties: crucial for the final application.

Acrylamide in Bakery Products: A Review on Health Risks, Legal Regulations and Strategies to Reduce Its Formation

Acrylamide is a contaminant as defined in Council Regulation (EEC) No 315/93 and as such, it is considered a chemical hazard in the food chain. The toxicity of acrylamide has been acknowledged since 2002, among its toxicological effects on humans being neurotoxicity, genotoxicity, carcinogenicity, and reproductive toxicity. Acrylamide has been classified as carcinogenic in the 2A group, with human exposure leading to progressive degeneration of the peripheral and central nervous systems characterized by cognitive and motor abnormalities. Bakery products (bread, crispbread, cakes, batter, breakfast cereals, biscuits, pies, etc.) are some of the major sources of dietary acrylamide. The review focuses on the levels of acrylamide in foods products, in particular bakery ones, and the risk that resulting dietary intake of acrylamide has on human health. The evolving legislative situation regarding the acrylamide content from foodstuffs, especially bakery ones, in the European Union is discussed underlining different measures that food producers must take in order to comply with the current regulations regarding the acrylamide levels in their products. Different approaches to reduce the acrylamide level in bakery products such as the use of asparginase, calcium salts, antioxidants, acids and their salts, etc., are described in detail.