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.

A Novel L-Asparaginase from Hyperthermophilic Archaeon Thermococcus sibiricus: Heterologous Expression and Characterization for Biotechnology Application

L-asparaginase (L-ASNase) is a vital enzyme with a broad range of applications in medicine and food industry. Drawbacks of current commercial L-ASNases stimulate the search for better-producing sources of the enzyme, and extremophiles are especially attractive in this view. In this study, a novel L-asparaginase originating from the hyperthermophilic archaeon Thermococcus sibiricus (TsA) was expressed in Escherichia coli, purified and characterized. The enzyme is optimally active at 90 °C and pH 9.0 with a specific activity of 2164 U/mg towards L-asparagine. Kinetic parameters KM and Vmax for the enzyme are 2.8 mM and 1200 µM/min, respectively. TsA is stable in urea solutions 0-6 M and displays no significant changes of the activity in the presence of metal ions Ni2+, Cu2+, Mg2+, Zn2+ and Ca2+ and EDTA added in concentrations 1 and 10 mmol/L except for Fe3+. The enzyme retains 86% of its initial activity after 20 min incubation at 90 °C, which should be enough to reduce acrylamide formation in foods processed at elevated temperatures. TsA displays strong cytotoxic activity toward cancer cell lines K562, A549 and Sk-Br-3, while normal human fibroblasts WI-38 are almost unsensitive to it. The enzyme seems to be a promising candidate for further investigation and biotechnology application.

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.

Bioprocess development for L-asparaginase production by Streptomyces rochei, purification and in-vitro efficacy against various human carcinoma cell lines

In the near future, the demand for L-asparaginase is expected to rise several times due to an increase in its clinical and industrial applications in various industrial sectors, such as food processing. Streptomyces sp. strain NEAE-K is potent L-asparaginase producer, isolated and identified as new subsp. Streptomyces rochei subsp. chromatogenes NEAE-K and the sequence data has been deposited under accession number KJ200343 at the GenBank database. Sixteen different independent factors were examined for their effects on L-asparaginase production by Streptomyces rochei subsp. chromatogenes NEAE-K under solid state fermentation conditions using Plackett-Burman design. pH, dextrose and yeast extract were the most significant factors affecting L-asparaginase production. Thus, using central composite design, the optimum levels of these variables were determined. L-asparaginase purification was carried out by ammonium sulfate followed by DEAE-Sepharose CL-6B ion exchange column with a final purification fold of 16.18. The monomeric molecular weight of the purified L-asparaginase was 64 kD as determined by SDS-PAGE method. The in vitro effects of L-asparaginase were evaluated on five human tumor cell lines and found to have a strong anti-proliferative effects. The results showed that the strongest cytotoxic effect of L-asparaginase was exerted on the HeLa and HepG-2 cell lines (IC50 = 2.16 ± 0.2 and 2.54 ± 0.3 U/mL; respectively). In addition, the selectivity index of L-asparaginase against HeLa and HepG-2 cell lines was 3.94 and 3.35; respectively.

Novel site-specific PEGylated L-asparaginase

L-asparaginase (ASNase) from Escherichia coli is currently used in some countries in its PEGylated form (ONCASPAR, pegaspargase) to treat acute lymphoblastic leukemia (ALL). PEGylation refers to the covalent attachment of poly(ethylene) glycol to the protein drug and it not only reduces the immune system activation but also decreases degradation by plasmatic proteases. However, pegaspargase is randomly PEGylated and, consequently, with a high degree of polydispersity in its final formulation. In this work we developed a site-specific N-terminus PEGylation protocol for ASNase. The monoPEG-ASNase was purified by anionic followed by size exclusion chromatography to a final purity of 99%. The highest yield of monoPEG-ASNase of 42% was obtained by the protein reaction with methoxy polyethylene glycol-carboxymethyl N-hydroxysuccinimidyl ester (10kDa) in 100 mM PBS at pH 7.5 and PEG:ASNase ratio of 25:1. The monoPEG-ASNase was found to maintain enzymatic stability for more days than ASNase, also was resistant to the plasma proteases like asparaginyl endopeptidase and cathepsin B. Additionally, monoPEG-ASNase was found to be potent against leukemic cell lines (MOLT-4 and REH) in vitro like polyPEG-ASNase. monoPEG-ASNase demonstrates its potential as a novel option for ALL treatment, being an inventive novelty that maintains the benefits of the current enzyme and solves challenges.

Isolation, Purification, Characterisation and Application of L-ASNase: A Review

BACKGROUND

L-ASNase (L-asparagine aminohydrolase EC 3.5.1.1) is used for the conversion of L-asparagine to L-aspartic acid and ammonia and also it was found as an agent of chemotherapeutic property according to recent patents. It is known as an anti-cancer agent and recently it has received an immense attention. Various microorganisms have the ability to secrete the L-ASNase. It is famous world-wide as anti-tumor medicine for acute lymphoblastic leukemia and lymphosarcoma. L-ASNase helps in deamination of Asparagine and Glutamine.

SOURCE

L-ASNase mainly found in two bacterial sources; Escherichia coli and Erwinia carotovora. Isolation from plants: Endophytes were also a great source of L-ASNase. It was isolated from four types of plants named as; C. citratus, O. diffusa, M. koengii, and also P. bleo.

APPLICATIONS

L-ASNase is used as a potential anti-tumor medicine. It plays a very much essential role for the growth of tumor cells. Tumor cells require a lot of asparagine for their growth. But ASNase converts to aspartate and ammonia from asparagine. So the tumor cell does not proliferate and fails to survive. The L-ASNase is used as the medicine for the major type of cancer like acute lymphocytic leukemia (ALL), brain. It also used as a medicine for central nervous system (CNS) tumors, and also for neuroblastoma. Two types of L-ASNase have been found.

CONCLUSION

L-ASNase becomes a powerful anti-tumor medicine and researchers should develop a potent strain of asparaginase which can produce asparaginase in the industrial level. It is also used in the pharmaceutical industry and food industry on a broader scale.

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

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

L-Asparaginase from Streptomyces griseus NIOT-VKMA29: optimization of process variables using factorial designs and molecular characterization of L-asparaginase gene

Marine actinobacteria are known to be a rich source for novel metabolites with diverse biological activities. In this study, a potential extracellular L-asparaginase was characterised from the Streptomyces griseus NIOT-VKMA29. Box-Behnken based optimization was used to determine the culture medium components to enhance the L-asparaginase production. pH, starch, yeast extract and L-asparagine has a direct correlation for enzyme production with a maximum yield of 56.78 IU mL(-1). A verification experiment was performed to validate the experiment and more than 99% validity was established. L-Asparaginase biosynthesis gene (ansA) from Streptomyces griseus NIOT-VKMA29 was heterologously expressed in Escherichia coli M15 and the enzyme production was increased threefold (123 IU mL(-1)) over the native strain. The ansA gene sequences reported in this study encloses several base substitutions with that of reported sequences in GenBank, resulting in altered amino acid sequences of the translated protein.

Engineering of Helicobacter pylori L-asparaginase: characterization of two functionally distinct groups of mutants

Bacterial L-asparaginases have been used as anti-cancer drugs for over 4 decades though presenting, along with their therapeutic efficacy, several side effects due to their bacterial origin and, seemingly, to their secondary glutaminase activity. Helicobacter pylori type II L-asparaginase possesses interesting features, among which a reduced catalytic efficiency for L-GLN, compared to the drugs presently used in therapy. In the present study, we describe some enzyme variants with catalytic and in vitro cytotoxic activities different from the wild type enzyme. Particularly, replacements on catalytic threonines (T16D and T95E) deplete the enzyme of both its catalytic activities, once more underlining the essential role of such residues. One serendipitous mutant, M121C/T169M, had a preserved efficiency vs L-asparagine but was completely unable to carry out L-glutamine hydrolysis. Interestingly, this variant did not exert any cytotoxic effect on HL-60 cells. The M121C and T169M single mutants had reduced catalytic activities (nearly 2.5- to 4-fold vs wild type enzyme, respectively). Mutant Q63E, endowed with a similar catalytic efficiency versus asparagine and halved glutaminase efficiency with respect to the wild type enzyme, was able to exert a cytotoxic effect comparable to, or higher than, the one of the wild type enzyme when similar asparaginase units were used. These findings may be relevant to determine the role of glutaminase activity of L-asparaginase in the anti-proliferative effect of the drug and to shed light on how to engineer the best asparaginase/glutaminase combination for an ever improved, patients-tailored therapy.

[Cross-immunogenicity of various bacterial L-asparaginases]

AIM

Evaluate immune response in mice against various L-asparaginases and determine their cross-immunogenicity.

MATERIALS AND METHODS

The studies were carried out in C57Bl(6j) line mice. Immunogenicity of L-asparaginases was studied: Escherichia coli type II (recombinant) (Medak, Germany) (EcA); Erwinia carotovora type II (ErA); Yersinia pseudotuberculosis type II (YpA); Rhodospirillum rubrum type I (RrA); Wollinella succinogenes type II (WsA). Immune response against the administered antigens was determined in EIA.

RESULTS

Y. pseudotuberculosis L-asparaginase was the most immunogenic, E. coli--the least immunogenic. E. carotovora, R. rubrum, W. succinogenes asparaginases displayed intermediate immunogenicity. The results of cross-immunogenicity evaluation have established, that blood sera of mice, that had received YpA, showed cross-immunogenicity against all the other L-asparaginase preparations except E. carotovora. During immunization with E. coli L-asparaginase the developed antibodies also bound preparation from E. carotovora. Sera from mice immunized with W. succinogenes, E. carotovora and R. rubrum L-asparaginases had cross-reaction only with EcA and did not react with other preparations.

CONCLUSION

Cross-immunogenicity of the studied L-asparaginases was determined. A sequence of administration of the studied preparation is proposed that allows to minimize L-asparaginase neutralization by cross-reacting antibodies.

Purification and characterization of a novel and robust L-asparaginase having low-glutaminase activity from Bacillus licheniformis: in vitro evaluation of anti-cancerous properties

L-asparaginase having low glutaminase has been a key therapeutic agent in the treatment of acute lymphpoblastic leukemia (A.L.L). In the present study, an extracellular L-asparaginase with low glutaminase activity, produced by Bacillus licheniformis was purified to homogeneity. Protein was found to be a homotetramer of 134.8 KDa with monomeric size of 33.7 KDa and very specific for its natural substrate i.e. L-asparagine. The activity of purified L-asparaginase enhanced in presence of cations including Na+ and K+, whereas it was moderately inhibited in the presence of divalent cations and thiol group blocking reagents. The purified enzyme was maximally active over the range of pH 6.0 to 10.0 and temperature of 40°C and enzyme was stable maximum at pH 9.0 and -20°C. CD spectra of L-asparaginase predicted the enzyme to consist of 63.05% α-helix and 3.29% β-sheets in its native form with T222 of 58°C. Fluorescent spectroscopy showed the protein to be stable even in the presence of more than 3 M GdHCl. Kinetic parameters Km, Vmax and kcat of purified enzyme were found as 1.4×10(-5) M, 4.03 IU and 2.68×10(3) s(-1), respectively. The purified L-asparaginase had cytotoxic activity against various cancerous cell lines viz. Jurkat clone E6-1, MCF-7 and K-562 with IC50 of 0.22 IU, 0.78 IU and 0.153 IU respectively. However the enzyme had no toxic effect on human erythrocytes and CHO cell lines hence should be considered potential candidate for further pharmaceutical use as an anticancer drug.

Cloning, expression, and characterization of L-asparaginase from a newly isolated Bacillus subtilis B11-06

This study focused on the cloning, overexpression, and characterization of the gene encoding L-asparaginase (ansZ) from a nonpathogenic strain of Bacillus subtilis B11-06. The recombinant enzyme showed high thermostability and low affinity to L-glutamine. The ansZ gene, encoding a putative L-asparaginase II, was amplified by PCR and expressed in B. subtilis 168 using the shuttle vector pMA5. The activity of the recombinant enzyme was 9.98 U/mL, which was significantly higher than that of B. subtilis B11-06. The recombinant enzyme was purified by a two-step procedure including ammonium sulfate fractionation and hydrophobic interaction chromatography. The optimum pH and temperature of the recombinant enzyme were 7.5 and 40 °C, respectively. The enzyme was quite stable at a pH range of 6.0-9.0 and exhibited about 14.7 and 9.0% retention of activity following 2 h incubation at 50 or 60 °C, respectively. The Km for L-asparagine was 0.43 mM, and the Vmax was 77.51 μM/min. Results of this study also revealed the potential industrial application of this enzyme in reducing acrylamide formation during the potato frying process.

[Physicochemical properties and antiproliferative activity of recombinant Yersinia pseudotuberculosis L-asparaginase]

The physicochemical, catalytic, and antiproliferative activity of a recombinant L-asparaginase from Yersinia pseudotuberculosis (YpA) have been studied. The following results were obtained: the K(M) value for L-asparagine is 17 +/- 0.9 microM, the optimal temperature is 60 degrees C, pH is 8.0, pI is 5.4 +/- 0.3, the L-glutaminase activity is no more than 5-6% of the L-asparaginase activity, and the antiproliferative activity on the Fisher L5178y lymphadenosis cell line comprised T/C = 136% (p < 0.001) at a 15% recovery rate. The described characteristic allows one to regard YpA as an antitumor enzyme with biological features similar to the L-asparaginase of E. coli.

Efficient production of L-asparaginase from Bacillus licheniformis with low-glutaminase activity: optimization, scale up and acrylamide degradation studies

L-Asparaginase has potential as an anti-cancer drug and for prevention of acrylamide formation in fried and baked foods. Production of the enzyme by Bacillus licheniformis (RAM-8) was optimized by process engineering using a statistical modeling approach and a maximum yield of 32.26 IU/ml was achieved. The L-asparaginase exhibited glutaminase activity of only 0.8 IU/ml and would therefore be less prone to cause the side effects associated with asparaginase therapy compared to enzyme preparations with higher glutaminase activities. When production was carried out in a 30-L bioreactor, enzyme production reached 29.94 IU/ml in 15 h. The enzyme inhibited poly-acrylamide formation in 10% acrylamide solution and reduced acrylamide formation in fried potatoes by 80%.

Studies on pH and thermal stability of novel purified L-asparaginase from Pectobacterium carotojorum MTCC 1428

Glutaminase free L-asparaginase is known to be an excellent anticancer agent. In the present study, the combined effect of pH and temperature on the performance of purified novel L-asparaginase from Pectobacterium carotovorum MTCC 1428 was studied under assay conditions using response surface methodology (RSM). Deactivation studies and thermodynamic parameters of this therapeutically important enzyme were also investigated. The optimum pH and temperature of the purified L-asparaginase were found to be 8.49 and 39.3 degrees C, respectively. The minimum deactivation rate constant (k(d)) and maximum half life (t1/2) were found to be 0.041 min(-1) and 16.9 h, respectively at pH of 8.6 and 40 degreesC. Thermodynamic parameters (deltaG, deltaH, deltaS, and activation energies) were also evaluated for purified L-asparaginase. The probable mechanism of deactivation of purified L-asparaginase was explained to an extent on the basis of deactivation studies and thermodynamic parameters.

Purification and characterization of glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428

An intracellular glutaminase-free L-asparaginase from Pectobacterium carotovorum MTCC 1428 was isolated to apparent homogeneity. The homotetramer enzyme has a molecular mass of 144.4 kDa (MALDI-TOF MS) and an isoelectric point of approximately 8.4. The enzyme is very specific for its natural substrate, L-asparagine. The activity of L-asparaginase is activated by mono cations and various effectors including Na+, K+, L-cystine, L-histidine, glutathione and 2-mercaptoethanol whereas it is moderately inhibited by various divalent cations and thiol group blocking reagents. Kinetic parameters, Km, Vmax and kcat of purified L-asparaginase from P. carotovorum MTCC 1428 were found to be 0.657 mM, 4.45 U μg(-1) and 2.751×10(3) s(-1), respectively. Optimum pH of purified L-asparaginase for the hydrolysis of L-asparagine was in the range of 8.0-10.0, and its optimum temperature was found to be 40 °C. The purified L-asparaginase has no partial glutaminase activity, which can reduce the possibility of side effects during the course of anti-cancer therapy.

Withania somnifera (Ashwagandha): a novel source of L-asparaginase

Different parts of plant species belonging to Solanaceae and Fabaceae families were screened for L-asparaginase enzyme (E.C.3.5.1.1.). Among 34 plant species screened for L-asparaginase enzyme, Withania somnifera L. was identified as a potential source of the enzyme on the basis of high specific activity of the enzyme. The enzyme was purified and characterized from W. somnifera, a popular medicinal plant in South East Asia and Southern Europe. Purification was carried out by a combination of protein precipitation with ammonium sulfate as well as Sephadex-gel filtration. The purified enzyme is a homodimer, with a molecular mass of 72 +/- 0.5 kDa as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size exclusion chromatography. The enzyme has a pH optimum of 8.5 and an optimum temperature of 37 degrees C. The Km value for the enzyme is 6.1 x 10(-2) mmol/L. This is the first report for L-asparaginase from W. somnifera, a traditionally used Indian medicinal plant.

L-Asparaginase: A Promising Chemotherapeutic Agent

This article comprises detailed information about L-asparaginase, encompassing topics such as microbial and plant sources of L-asparaginase, treatment with L-asparaginase, mechanism of action of L-asparaginase, production, purification, properties, expression and characteristics of l-asparaginase along with information about studies on the structure of L-asparaginase. Although L-asparaginase has been reviewed by Savitri and Azmi (2003), our effort has been to include recent and updated information about the enzyme covering new aspects such as structural modification and immobilization of L-asparaginase, recombinant L-asparaginase, resistance to L-asparaginase, methods of assay of L-asparagine and L-asparaginase activity using the biosensor approach, L-asparaginase activity in soil and the factors affecting it. Also, side-effects of L-asparaginase treatment in acute lymphoblastic leukemia (ALL) have been discussed in the current review. L-asparaginase has been and is still one of the most widely studied therapeutic enzymes by researchers and scientists worldwide.

Expression, purification and crystallization of Helicobacter pylori L-asparaginase

The L-asparaginases from Escherichia coli and Erwinia chrysanthemi are effective drugs that have been used in the treatment of acute childhood lymphoblastic leukaemia for over 30 years. However, despite their therapeutic potential, they can cause serious side effects as a consequence of their intrinsic glutaminase activity, which leads to L-glutamine depletion in the blood. Consequently, new asparaginases with low glutaminase activity, fewer side effects and high activity towards L-asparagine are highly desirable as better alternatives in cancer therapy. L-Asparaginase from Helicobacter pylori was overexpressed in E. coli and purified for structural studies. The enzyme was crystallized at pH 7.0 in the presence of 16-19%(w/v) PEG 4000 and 0.1 M magnesium formate. Data were collected to 1.6 A resolution at 100 K from a single crystal at a synchrotron-radiation source. The crystals belong to space group I222, with unit-cell parameters a = 63.6, b = 94.9, c = 100.2 A and one molecule of L-asparaginase in the asymmetric unit. Elucidation of the crystal structure will provide insight into the active site of the enzyme and a better understanding of the structure-activity relationship in L-asparaginases.

Partial purification and anti-leukemic activity of L-asparaginase enzyme of the actinomycete strain LA-29 isolated from the estuarine fish, Mugil cephalus (Linn.)

The actinomycete strain LA-29 isolated from the gut contents of the fish, Mugil cephalus of the Vellar estuary showed excellent L-asparaginase activity The enzyme was purified 18-fold and the final recovery of protein was 1.9%, which exhibited an activity of 13.57 IU/mg protein. The partially purified L-asparaginase inhibited the growth of leukemia cells in male wistar rats. Average survival period of the rats was more in an optimum enzyme dose of 100 units and the survival period was less when the dosages were increased and at the same time the enzyme became less effective when the dosages were decreased. Higher survival of 17.2 days was recorded when 100 units of the enzyme was given in three intermittent doses (50/25/25 units) at the interval of 24 hr. Analysis of cell components of the strain LA-29 has revealed the wall type-I which is the characteristic of the genus Streptomyces. Further the morphological, physiological and biochemical features along with the micromorphological results obtained for the strain LA-29 were compared with that of the Streptomyces species found in Bergey's Manual of Determinative Bacteriology and the strain LA-29 has been tentatively identified as Streptomyces canus.

Probing the antigenicity of E. coli L-asparaginase by mutational analysis

A strategy, termed alanine-scanning mutagenesis, was used to identify the amino acid residues which are critical to the antigenicity of Escherichia coli L-asparaginase (L-ASP). Three continuous alkaline residues, 195RKH197, were mutated to Ala selectively. Four mutant recombinant L-ASPs were constructed and expressed in E. coli, and then purified. The purified mutants showed a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and were more than 95% pure by reverse high-performance liquid chromatography. The activities of wild-type and mL-ASPs in the fermentative medium were all about 130 U/mL. The change from 195RKH197 to 195AAA197 reduced the antigenicity of the enzyme greatly as shown in competition enzyme-linked immunosorbent assay using polyclonal antibodies raised against the wild-type L-ASP from rabbits. The results show that residues 195RKH197 of E. coli L-ASP are critical to its antigenicity.

In situ extraction of intracellular l-asparaginase using thermoseparating aqueous two-phase systems

The feasibility and generic applicability of directly integrating conventional discrete operations of cell disruption by high pressure homogenizer and the product capture by aqueous two-phase extraction (ATPE) system have been demonstrated for the extraction of intracellular L-asparaginase from E. coli. In a side-by-side comparison with the conventional ATPE process, including cell disruption, centrifugal clarification and following ATPE, purification of L-asparaginase via this novel in situ ATPE process yielded a product of L-asparaginase with a higher specific activity of 94.8 U/(mg protein) and a higher yield of 73.3%, both of which in the conventional ATPE process were 78.6 U/(mg protein) and 52.1%, respectively. In the purification of L-asparaginase (pI=4.9), product-debris interactions commonly diminish its recovery. It was demonstrated that immediate extraction of L-asparaginase in ATPE systems when it is released at pH 5.0 during cell disruption effectively increased its recovery in the top phase due to the reduced interaction between L-asparaginase and cell debris and the reduced degradation by contaminated protease. In addition, no clarification step and/or disruptate storage are required in this in situ ATPE, which reduced the number of unit operations and thus shortened the overall process time. This novel process has a good potential for the separation of other intracellular biological products.

Purification of L-asparaginase from a bacteria Erwinia carotovora and effect of a dihydropyrimidine derivative on some of its kinetic parameters

L-Asparaginase shows antileukemic activity and is generally administered in the body in combination with other anticancer drugs like pyrimidine derivatives. In the present study, L-asparaginase was purified from a bacteria Erwinia carotovora and the effect of a dihydropyrimidine derivative (1-amino-6-methyl-4-phenyl-2-thioxo, 1,2,3,4-tetrahydropyrimidine-5-carboxylic acid methyl ester) was studied on the kinetic parameters Km and Vmax of the enzyme using L-asparagine as substrate. The enzyme had optimum activity at pH 8.6 and temperature 35 degrees C, both in the absence and presence of pyrimidine derivative and substrate saturation concentration at 6 mg/ml. For the enzymatic reaction in the absence and presence (1 to 3 mg/ml) of dihydropyrimidine derivative, Km values were 7.14, 5.26, 4.0, and 5.22 M, and Vmax values were 0.05, 0.035, 0.027 and 0.021 mg/ml/min, respectively. The kinetic values suggested that activity of enzyme was enhanced in the presence of dihydropyrimidine derivative.

Effect of Vitreoscilla hemoglobin on production of a chemotherapeutic enzyme, L-asparaginase, by Pseudomonas aeruginosa

The production of L-asparaginase, an enzyme widely used in cancer chemotherapy, is mainly regulated by carbon catabolite repression and oxygen. This study was carried out to understand how different carbon sources and Vitreoscilla hemoglobin (VHb) affect the production of this enzyme in Pseudomonas aeruginosa and its VHb-expressing recombinant strain (PaJC). Both strains grown with various carbon sources showed a distinct profile of the enzyme activity. Compared to no carbohydrate supplemented medium, glucose caused a slight repression of L-asparaginase in P. aeruginosa, while it stimulated it in the PaJC strain. Glucose, regarded as one of the inhibitory sugars for the production L-asparaginase by other bacteria, was determined to be the favorite carbon source compared to lactose, glycerol and mannitol. Furthermore, contrary to common knowledge of oxygen repression of L-asparaginase in other bacteria, oxygen uptake provided by VHb was determined to even stimulate the L-asparaginase synthesis by P. aeruginosa. This study, for the first time, shows that in P. aeruginosa utilizing a recombinant oxygen uptake system, VHb, L-asparaginase synthesis is stimulated by glucose and other carbohydrate sources compared to the host strain. It is concluded that carbon catabolite and oxygen repression of L-asparaginase in fermentative bacteria is not the case for a respiratory non-fermentative bacterium like P. aeruginosa.

Pharmacological and clinical evaluation of L-asparaginase in the treatment of leukemia

L-Asparaginase is an effective antineoplastic agent, used in the acute lymphoblastic leukemia chemotherapy. It has been an integral part of combination chemotherapy protocols of pediatric acute lymphoblastic leukemia for almost 3 decades. The potential of L-asparaginase as a drug of leukemia has been a matter of discussion due to the high rate of allergic reactions exhibited by the patients receiving the medication of this enzyme drug. Frequent need of intramuscular injection has been another disadvantage associated with the native preparation. However, of late these clinical complications seem to have been addressed by modified versions of L-asparaginase. PEG-L-asparaginase proves to be most effective in this regard. It becomes important to discuss the efficacy of L-asparaginase as an antileukemic drug vis-a-vis these disadvantages. In this review, an attempt has been made to critically evaluate the pharmacological and clinical potential of various preparations of L-asparaginase as a drug. Advantages of PEG-L-asparaginase over native preparations and historical developments of therapy with l-asparaginase have also been outlined in the review below.

Synthesis, characterization and immunogenicity of silk fibroin-l-asparaginase bioconjugates

L-asparaginase (ASNase) is one basic drug in the treatment of acute lymphoblastic leukemia (ALL). Because its half-life time is too short and it is easy to arouse allergic reaction, use in practical clinic is considerably limited. Silk fibroin (SF) with different molecular mass from 40 to 120 kDa is a natural biocompatible protein and could be used as a novel bioconjugate for enzyme modification to overcome its usual shortcomings mentioned above. When the enzyme was bioconjugated covalently with the water-soluble fibroin by glutaraldehyde, the enzyme kinetic properties and immune characteristics in vivo of the resulting silk fibroin-L-asparaginase (SF-ASNase) bioconjugates were investigated in detail. The results show that the modified ASNase was characterized by its higher residual activity (nearly 80%), increased heat and storage stability and resistance to trypsin digestion, and its longer half-life (63 h) than that of intact ASNase (33 h). The abilities of intact and modified ASNases to arouse allergic reaction are 2(4) and 2(1) antibody titers, respectively. Bioconjugation of silk fibroin significantly helps to reduce the immunogenicity and antigenicity of the enzyme. The apparent Michaelis constants of the modified ASNase (K(m(app))=0.844 x 10(-3)mol L(-1)) was approximately six times lower than that of enzyme alone, which suggests that the affinity of the enzyme to substrate l-asparagine elevated when bioconjugated covalently with silk fibroin. SF-ASNase bioconjugates could overcome the common shortcomings of the native form. Therefore, the modified ASNase coupled with silk fibroin has the potential values of being studied and developed as a new bioconjugate drug.

Extracellular expression and single step purification of recombinant Escherichia coli L-asparaginase II

L-Asparaginase (isozyme II) from Escherichia coli is an important therapeutic enzyme used in the treatment of leukemia. Extracellular expression of recombinant asparaginase was obtained by fusing the gene coding for asparaginase to an efficient pelB leader sequence and an N-terminal 6x histidine tag cloned under the T7lac promoter. Media composition and the induction strategy had a major influence on the specificity and efficiency of secretion of recombinant asparaginase. Induction of the cells with 0.1 mM IPTG at late log phase of growth in TB media resulted in fourfold higher extracellular activity in comparison to growing the cells in LB media followed by induction during the mid log phase. Using an optimized expression strategy a yield of 20,950 UI/L of recombinant asparaginase was obtained from the extracellular medium. The recombinant protein was purified from the culture supernatant in a single step using Ni-NTA affinity chromatography which gave an overall yield of 95 mg/L of purified protein, with a recovery of 86%. This is approximately 8-fold higher to the previously reported data in literature. The fluorescence spectra, analytical size exclusion chromatography, and the specific activity of the purified protein were observed to be similar to the native protein which demonstrated that the protein had folded properly and was present in its active tetramer form in the culture supernatant.

Optimization of extracellular production of recombinant asparaginase in Escherichia coli in shake-flask and bioreactor

Various host-vector combinations were tested to maximize the extracellular production of recombinant asparaginase in Escherichia coli. Expression of recombinant asparaginase fused to pelB leader sequence under the inducible T7lac promoter in BLR (DE3) host cells resulted in optimum extracellular production in shake-flasks. Fed-batch studies were carried out using this recombinant strain and an exponential feeding strategy was used to maintain a specific growth rate of 0.3 h(-1). To check the effect of the time of induction on expression, cultures were induced with 1 mM isopropyl-beta-D-thiogalactopyranoside at varying cell optical densities (OD(600): 33, 60, 90, 135). Although the specific product formation rates declined with increasing OD of induction, a maximum volumetric activity of 8.7 x 10(5) units l(-1), corresponding to approximately 5.24 g l(-1) of recombinant asparaginase, was obtained when induction was done at an OD(600) of 90. The recombinant protein was purified directly from the culture medium, using a rapid two-step purification strategy, which resulted in a recovery of approximately 70% and a specific activity of approximately 80% of that of the native enzyme.

Production, Isolation, and Purification of L-Asparaginase from Pseudomonas Aeruginosa 50071 Using Solid-state Fermentation

The L-asparaginase (E. C. 3. 5. 1. 1) enzyme was purified to homogeneity from Pseudomonas aeruginosa 50071 cells that were grown on solid-state fermentation. Different purification steps (including ammonium sulfate fractionation followed by separation on Sephadex G-100 gel filtration and CM-Sephadex C50) were applied to the crude culture filtrate to obtain a pure enzyme preparation. The enzyme was purified 106-fold and showed a final specific activity of 1900 IU/mg with a 43% yield. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the purified enzyme revealed it was one peptide chain with M(r) of 160 kDa. A Lineweaver-Burk analysis showed a K(m) value of 0.147 mM and V(max) of 35.7 IU. The enzyme showed maximum activity at pH 9 when incubated at 37 degrees C for 30 min. The amino acid composition of the purified enzyme was also determined.

Modeling of Monolith-Supported Affinity Chromatography

Ceramic monoliths have been used successfully as active support for affinity chromatography (1). A mathematical model was developed to simulate the adsorption-elution experimental behavior of asparaginase in an agarose-coated monolith support. The computer-based model allows precise determination of experimental parameters. Because of the simple geometry of ceramic monoliths used as support, the mathematical model can be used to design adsorption/elution cycles for the large throughput separation of biomolecules.

One-step purification and kinetic properties of the recombinant l-asparaginase from Erwinia carotovora

ECAR-LANS, the recombinant L-asparaginase from Erwinia carotovora, is a prospective therapeutic enzyme for leukaemia treatment. An efficient and economical scheme was developed for the purification, cloning and expression in Eschericha coli of ECAR-LANS. More than 90% purity, complemented with 72% active enzyme recovery, was achieved with a single chromatographic purification step. The activity of purified L-asparaginase was 630 i.u./mg. The ECAR-LANS K (m) value was 98x10(-6) M for the main physiological substrate L-Asn and 3400x10(-6) M for L-Gln. ECAR-LANS was found to have low relative glutaminase activity (1.2%) at physiological concentrations of L-Asn and L-Gln in blood. Kinetic studies of ECAR-LANS showed that the recombinant asparaginase combined the main advantages of Erw. chrysanthemi and E. coli L-asparaginases II, currently used in the treatment of acute lymphoblastic leukaemia.

[Purification and properties of recombinant Erwinia carotovora L-asparaginase expressed in E.coli cells]

The method of purification Erwinia carotovora recombinant L-asparaginase, expressed in E.coli, including ultrasonic disintegration of biomass, fractionation ammonium sulfate and column chromatography on CM- or SP-Sepharose has been developed. According to SDS-PAAGE the enzyme preparation was homogeneous, its specific activity and yield consist respectively about 620 IU/mg of protein and 75%. Physical-chemical and structural properties of recombinant Erwinia carotovora L-asparaginase are similar to the enzymes from the wild strains Erwinia carotovora and recombinant L-asparaginase Erwinia chrysanthemi.

Use of ceramic monoliths as stationary phase in affinity chromatography

The use of coated ceramic monoliths as support for affinity chromatography is described. Ceramic monoliths are robust active matrix supports and present a very small pressure drop. Monoliths are coated with a very thin agarose gel layer and activated using a standard activation process for agarose beads. Experiments demonstrate that enzyme adsorption occurs exclusively on the outside surface of the agarose coating since enzyme molecules are too large to fit into the porous matrix. Adsorption and desorption rates are large and production of enzyme per unit monolith volume justifies further exploring this separation process for large throughput operation.

[Construction of a set of secreting expression vectors for Saccharomyces cerevisiea]

The DNA fragment ecoding the Signal peptide of inulinase of Kluyveromyces smarxianu was synthesized chemically. This fragment was cloned in-frame in the expression vector pYES2 of Saccharomyces cerevisiae, resulting in a set of new secreting expression vectors pYES2 I, pYES2 II, pYES2 III. The L-Asparaginase gene (ASN) of E. coli and alpha-acetylactate decarboxylase gene (ALDC) of B. brevis which were amplified by PCR and cloned into the new vectors respectively were transformed into Saccharomyces cerevisia, and most of enzyme activities were secreted into the medium. The new secreting expression vectors still have excellent segregational stability even after growth for 100 h in the absence of selective pressure.

Direct process integration of cell disruption and fluidised bed adsorption in the recovery of labile microbial enzymes

The practical feasibility and generic applicability of the direct integration of cell disruption by bead milling with the capture of intracellular products by fluidised bed adsorption has been demonstrated. Pilot-scale purification of the enzyme L-asparaginase from unclarified Erwinia chrysanthemi disruptates exploiting this novel approach yielded an interim product which rivalled or bettered that produced by the current commercial process employing discrete operations of alkaline lysis, centrifugal clarification and batch adsorption. In addition to improved yield and quality of product, the process time during primary stages of purification was greatly diminished. Two cation exchange adsorbents, CM HyperD LS (Biosepra/Life Technologies) and SP UpFront (custom made SP form of a prototype stainless steel/agarose matrix, UpFront Chromatography) were physically and biochemically evaluated for such direct product sequestration. Differences in performance with regard to product capacity and adsorption/desorption kinetics were demonstrated and are discussed with respect to the design of adsorbents for specific applications. In any purification of L-asparaginase (pI = 8.6), product-debris interactions commonly diminish the recovery of available product. It was demonstrated herein, that immediate disruptate exposure to a fluidised bed adsorbent promoted concomitant reduction of product in the liquid phase, which clearly counter-acted the product-debris interactions to the benefit of product yield.

Effects of polyethylene glycol attachment on physicochemical and biological stability of E. coli L-asparaginase

L-asparaginase obtained from E. coli strains is an important enzyme widely used in leukemia treatment. However, hypersensitivity reactions must be considered a relevant adverse effect of asparaginase therapy. One approach to reduce the hypersensitivity reactions caused by this enzyme is to change its physicochemical and biological properties by means of polyethylene glycol (PEG) conjugation, resulting in a less immunogenic enzyme with much longer half-time of plasmatic life. This work investigated the factors that could interfere in PEG-enzyme's stability. The complexation did not affect the range of pH activity and stability was improved in acid medium remaining stable during 1 h at pH 3.5. The PEG-enzyme exhibited activity restoration capacity (32% after 60 min) when subjected to temperatures of 65 degrees C in physiological solution. The PEG-enzyme in vitro assays showed a very high stability in a human serum sample, keeping its activity practically unchanged during 40 min (strength to non-specific antibodies or proteases in serum). An increase of PEG-enzyme catalytic activity during the lyophilization was observed. The process of modification of L-asparaginase with PEG improved both physicochemical and biological stability.

An inhibitory factor for cell-free protein synthesis from Salmonella enteritidis exhibits cytopathic activity against Chinese hamster ovary cells

A factor inhibiting cell-free protein synthesis was purified from Salmonella enteritidis cell lysate by sequential ammonium sulfate precipitation, chromatography on anion exchange and hydrophobic interaction columns, and polyacrylamide disc gel electrophoresis. The purified factor, which was named SIPS (Salmonella inhibitor of protein synthesis), inhibited in vitro protein synthesis in rabbit reticulocyte lysate and had a molecular mass of 38 kDa, estimated by PAGE under denaturing conditions. SIPS was also cytopathic for Chinese hamster ovary cells. The N-terminal amino acid sequence (20 residues) of SIPS was found to be identical to that of mature L-asparaginase II of Escherichia coli. Indeed, the purified SIPS exhibited asparaginase activity, E. coli L-asparaginase II had cytopathic activity and inhibited in vitro protein synthesis. The results suggest that at least a part of cytotoxicity and inhibition of cell-free protein synthesis caused by S. enteritidis is a property of the bacterial L-asparaginase.

L-asparaginase release from Escherichia coli cells with K2HPO4 and Triton X100

A method to release L-asparaginase (EC 3.5.1.1) from ATCC Escherichia coli 11303 cells by chemical permeabilization was studied. It was found that a combination of K2HPO4 and Triton X100 was effective. The influences of K2HPO4 concentration, Triton concentration, E. coli cell concentration and pH on the release of enzyme and proteins were investigated in detail. Experimental results showed that 12.5% (w/v) K2HPO4, 2% (w/v) Triton X100 and 3 x 10(8) cells/mL made the amount of enzyme released over 70%. L-Asparaginase in K2HPO4 and Triton solution could remain stable at least for 24 h. The release effect of K2HPO4 and Triton X100 used simultaneously was better than that of K2HPO4 and Triton X100 used separately in succession. Electron microscopy indicated that the chemical treatment altered the surface structure of E. coli cells but did not break them. As the method does not produce a large amount of cell fragments and the amount of enzyme released is relatively high, it can be thought to be an valuable and economic method to release intracellular enzyme.

Antitumor activity of L-asparaginase from Thermus thermophilus

L-asparaginase (EC 3.5.1.1) was purified to homogeneity from Thermus thermophilus. The apparent molecular mass of L-asparaginase was found to be 33 kDa by SDS-PAGE, whereas by Sephacryl S-300 superfine column it was found to be 200 kDa, indicating that the enzyme in the native stage acts as hexamer. It is a thermostable enzyme and keeps all of its activity at 80 degrees C for 10 min. The antiproliferative activity of the purified L-asparaginase from T. thermiphilus was tested against the following human cell lines: K-562 (chronic myelogenous leukemia), Raji (Burkitt's lymphoma), SK-N-MC (primitive neuroectodermal tumor), HeLa (cervical cancer), BT20 and MCF7 (breast cancers), HT-29 (human colon cancer), and OAW-42 (ovarian cancer). The antiproliferative activity of T. thermophilus enzyme was compared with Erwinase, the commercially available L-asparaginase from Erwinia corotovora. The potency difference between the two L-asparaginases was greater in HeLa and SK-N-MC than in other cell lines. The fact that L-asparaginase from T. thermophilus does not hydrolyse L-glutamine makes it advantageous for future clinical trials.

L-asparaginase of Thermus thermophilus: purification, properties and identification of essential amino acids for its catalytic activity

L-asparaginase EC 3.5.1.1 was purified to homogeneity from Thermus thermophilus. The apparent molecular mass of L-asparaginase by SDS-PAGE was found to be 33 kDa, whereas by its mobility on Sephacryl S-300 superfine column was around 200 kDa, indicating that the enzyme at the native stage acts as hexamer. The purified enzyme showed a single band on acrylamide gel electrophoresis with pI = 6.0. The optimum pH was 9.2 and the Km for L-asparagine was 2.8 mM. It is a thermostable enzyme and it follows linear kinetics even at 77 degrees C. Chemical modification experiments implied the existence ofhistidyl, arginyl and a carboxylic residues located at or near active site while serine and mainly cysteine seems to be necessary for active form.

[Bacterial L-asparaginase and glutamin(asparagin)ase: some properties, structure and anti-tumor activity]

Experimental material on structurally and functional organization, regulation of biosynthesis and activity, mechanism of action, genetic determinants, heterologous expression of bacterial L-asparaginases is accumulated. The modern approaches to isolation and purification of these enzymes, some questions of practical using in oncology in the schedules combined chemotherapy of leukemia the native and modified forms of L-asparaginases are discussed. The some results before carried out in the IBMC RAMS and number institutes of the Russia on study bacterial L-asparaginases and glutamine(asparagine)ases are summarized.

Crystallization and preliminary crystallographic studies of a new crystal form of Escherichia coli L--asparaginase II (Ser58Ala mutant)

Periplasmic Escherichia coli L-asparaginase II with an Ser58Ala mutation in the active-site cavity has been crystallized in a new orthorhombic form (space group P2(1)2(1)2). Crystals of this polymorph suitable for X-ray diffraction have been obtained by vapour diffusion using two sets of conditions: (i) 1% agarose gel using MPD as precipitant (pH 4.8) and (ii) liquid droplets using PEG-MME 550 (pH 9.0). The crystals grown in agarose gel are characterized by unit-cell parameters a = 226.9, b = 128.4, c = 61.9 A and diffract to 2.3 A resolution. The asymmetric unit contains six protein molecules arranged into one pseudo-222-symmetric homotetramer and an active-site competent dimer from which another homotetramer is generated by crystallographic symmetry.

A simple method for the isolation and purification of L-asparaginase from Enterobacter aerogenes

L-Asparaginase from Enterobacter aerogenes was purified by a simple method involving sonication of the crude cell mass, gel filtration with Sephacryl S-100 as the separating material, followed by ultrafiltration. Recent methods involve complex purification procedures of 5-6 steps. The isolation process resulted in 10-fold purification of the enzyme with a specific activity of 55 IU/mg protein and recovery of 54%. The purity was tested by capillary electrophoresis, used for the first time for documenting the purification of L-asparaginase. The choice of the column material was critical in the purification process.

Production and properties of L-asparaginase from Mucor species associated with a marine sponge (Spirastrella sp.)

The fungus Mucor sp. isolated from the marine sponge Spirastrella sp. produced extracellular L-asparaginase. The maximum L-asparaginase activity was found at 50 degrees C. The activation and deactivation energies of the partially purified enzyme were 9.58 and 21.69 kcal mol-1, respectively. The enzyme activity was not affected by the addition of 4% (w/v) NaCl and different metal ions (Co+2, Fe+2, Mg+2, Ni+2, and Zn+2) at 25 mmol l-1 but was strongly inhibited by EDTA.

Purification and preliminary characterization of L-asparaginase from Erwinia aroideae NRRL B-138

L-Asparaginase (L-asparagine amidohydrolase EC 3.5.1.1) from Erwinia aroideae NRRL B-138 has been purified to apparent homogeneity by ammonium sulphate precipitation, chromatography on sulfopropyl-sephadex C-50 and sephadex G-200 with 22% recovery and 567-fold purification. The enzyme obtained from sulfopropyl-sephadex C-50 was unstable and lost activity within a few hours. Addition of glycerol helped in restoring the activity of the enzyme. The enzyme has an apparent molecular mass of approximately 155 kDa and has four subunits of identical molecular mass of approximately 38 kDa. The K(m) for L-asparagine is 2.8 x 10(-3) M. Enzyme shows optimal activity at 45 degrees C and pH 8.2. Energy of activation as determined from Arrhenius plot was 9.1 kcal/mol. Substrate L-asparagine and analogue L-glutamine, D-asparagine and 6 diazo-5-oxo-L-norleucine provide full protection to the enzyme against thermal denaturation.

Guinea pig serum L-asparaginase: purification, and immunological relationship to liver L-asparaginase and serum L-asparaginases in other mammals

L-asparaginase, an enzyme used in the treatment of acute lymphocytic leukemia, is found in the serum of only a few mammalian groups, including the guinea pig and its close relatives in the superfamily Cavioidea. This report describes the purification and characterization of L-asparaginase from guinea pig serum. Antiserum against the purified enzyme cross-reacted with sera from other Cavioidean species but not with mouse serum. Relatively weak cross-reaction with unpurified L-asparaginase in guinea pig liver indicates a significant degree of evolutionary divergence.

Purification, characterization and antitumor activity of L-asparaginase isolated from Pseudomonas stutzeri MB-405

An L-asparaginase produced by Pseudomonas stutzeri MB-405 was isolated and characterized. After initial ammonium sulfate fractionation, the enzyme was purified by consecutive column chromatography on Sephadex G-100, Ca-hydroxylapatite, and DEAE-Sephadex A-50. The 665.5-fold purified enzyme thus obtained has the specific activity of 732.3 units mg protein-1 with an overall recovery of 27.2%. The apparent M(r) of the enzyme under nondenaturing and denaturing conditions was 34 kDa and 33 kDa respectively, and the isoelectric point was 6.38 +/- 0.02. It displayed optimum activity at pH 9.0 and 37 degrees C. The enzyme was very specific for L-asparagine and did not hydrolyze L-glutaminate. The Km of the L-asparaginase was found to be 1.45 x 10(-4) M towards L-asparagine and was competitively inhibited by 5-diazo-4-oxo-L- norvaline (DONV) with a Ki of 0.03 mM. Metal ions such as Mn2+, Zn2+, Hg2+, Fe3+, Ni2+, and Cd2+ potentially inhibited the enzyme activity. The activity was enhanced in the presence of thiol-protecting reagents such as DTT, 2-ME, and glutathione (reduced), but inhibited by PCMB and iodoacetamide. The tumor inhibition study with Dalton's lymphoma tumor cells in vivo indicated that this enzyme possesses antitumor properties.

Extraction of extracellular L-asparaginase from Candida utilis

L-Asparaginase was extracted from Candida utilis cells using various reducing agents, 2-mercaptoethanol, dithiothreitol, or cysteine. The extraction of the enzyme depended upon the kind and concentration of reducing agents, temperature, time of incubation, and pH of buffer used. The enzyme was typically extracted by incubating the cells at 50 degrees C for 4 h in extraction solution containing 20 mM 2-mercaptoethanol in 20 mM potassium phosphate buffer (pH 7.0). The enzyme can be extracted from either cell precipitate or cell culture broth. The yeast cells were viable after extraction of L-asparaginase.

Acute parotitis during induction therapy including L-asparaginase in acute lymphoblastic leukemia

In a patient affected by acute lymphoblastic leukemia (ALL) and subjected to therapy with Erwinia L-asparaginase, acute parotitis was observed. Microbiological studies excluded any infectious etiology. Regression of parotitis was spontaneous. This complication has not been previously reported and could be due to the same mechanism of pancreatic injury. The occurrence of acute parotitis needs to be promptly recognized in order to avoid the continuation of L-asparaginase.