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.

Two forms of L-asparaginase in Tetrahymena thermophila

In T. thermophila two forms of L-asparaginase (EC 3.5.1.1) were extracted and purified to near homogeneity which are associated with membranes. These two forms of L-asparaginase, I or II, act optimally at pH 8.6 and do not present any glutaminase or kinase activity. Both activities reach maximal values at the stationary phase of growth of T. thermophila. L-Asparaginases are solubilized by treatment of the particulates with 2% w/v Triton X-100 and then by sodium phosphate buffer pH 8.0. Both forms cross reacted with antibodies raised against T. pyriformis L-asparaginase and show isoelectric points 7.4 and 8.2. Among the metals tested, Ca2+ is the most effective in activating L-asparaginase I or II activity. Sorbitol alone up to 30% w/v in the assay mixture activates more than 10 x fold the activity of L-asparaginase II. Incubation of L-asparaginase I or II with increasing concentration of phospholipase C results in gradually loss of their activities. The relative effectiveness of a variety of phospholipids to reconstitute enzyme activity is presented as well.

Fermentative production and isolation of L-asparaginase from Erwinia carotovora, EC-113

L-Asparaginase, an enzyme-drug used for the treatment of acute lymphoblastic leukemia was isolated from Erwinia carotovora. The effects of different carbon and nitrogen sources on the fermentative production of the enzyme were studied. Lactose, monosodium glutamate, corn steep liquor, tryptone and yeast extract showed significant stimulation of the production. When L-asparagine (0.2%), a substrate of the enzyme was added to a fermentation medium, a mutant strain EC-113 exhibited 6 times higher production indicating a distinct induction. The enzyme was extracted from the cells and purified about 30 fold to apparent homogeneity employing polyacrylamide gel electrophoresis. The methods used in sequence were DEAE cellulose chromatography, sephadex G-200 gel filtration, hydroxylapatite ion-exchange and affinity chromatography on sepharose CL-6B. The recovery of enzyme was 60%. The purified enzyme showed optimal pH at 8.0 and optimal temperature at 50 degrees C. The Km value of purified enzyme was 1.8 x 10(-5) M. LD50 of purified enzyme in mice by intravenous route was 4,80,000 IU/Kg and repeated treatment at 20,000 IU/Kg by intravenous route did not elicit bone marrow depression or damage to intestinal mucosa. The plasma half life was 14-24 hours and clearance time was 4-5 hours. Purified enzyme shows significant antitumor activity on experimental animal models.

Probing the role of threonine and serine residues of E. coli asparaginase II by site-specific mutagenesis

Site-specific mutagenesis has been used to probe amino acid residues proposed to be critical in catalysis by Escherichia coli asparaginase II. Thr12 is conserved in all known asparaginases. The catalytic constant of a T12A mutant towards L-aspartic acid beta-hydroxamate was reduced to 0.04% of wild type activity, while its Km and stability against urea denaturation were unchanged. The mutant enzyme T12S exhibited almost normal activity but altered substrate specificity. Replacement of Thr119 with Ala led to a 90% decrease of activity without markedly affecting substrate binding. The mutant enzyme S122A showed normal catalytic function but impaired stability in urea solutions. These data indicate that the hydroxyl group of Thr12 is directly involved in catalysis, probably by favorably interacting with a transition state or intermediate. By contrast, Thr119 and Ser122, both putative target sites of the inactivator DONV, are functionally less important.

L-asparaginase from developing seeds of Lupinus arboreus

Asparaginase (EC 3.5.1.1) activity reached a maximum 40 days post anthesis in developing seeds of Lupinus arboreus and this correlated with the appearance of other ammonia assimilatory enzymes. Asparaginase, purified from these developing seeds, was resolved into three isoforms, designated asparaginases A, B and C. A major protein species in asparaginase A preparations co-focussed with enzyme activity on an isoelectric focussing gel. When analysed by SDS-PAGE, asparaginase isoforms A and B each yielded several polypeptides with M(r)s in the 14,000 to 19,000 ranged. These peptides are fragmentation products of an M(r) 36,000 asparaginase subunit. Polyclonal antibodies raised against asparaginase isoforms A and B precipitated asparaginase activity from a partially purified L. arboreus seed extract. Immunoaffinity chromatography recovered polypeptides with M(r)s between 14,000 and 19,000. Partial protein sequences were obtained for these asparaginase polypeptides.

Rapid large-scale preparation of recombinant Erwinia chrysanthemi L-asparaginase

L-asparaginase from Erwinia provides an alternative to the enzyme from E. coli for the effective treatment of acute lymphoblastic leukaemia. A procedure was required for the large-scale partial purification of the recombinant Erwinia enzyme cloned and expressed in Erwinia. Enzyme was extracted from Erwinia at high pH and extraneous protein precipitated at low pH. S-Sepharose FF was selected as the medium of choice for the chromatography step since it was adequate for the high flow rates required (linear flow rate 315 cm h-1) and the methylsulphonate functional groups exploited the high pI of the enzyme by allowing binding of L-asparaginase at pH 4.8 while most of the other proteins passed through the column. The useful capacity of the matrix was up to 34 mg enzyme/ml matrix at a linear flow rate of 95 cm h-1 and 15.4 mg enzyme/ml matrix at a linear flow rate of 315 cm h-1. Weakly bound protein was removed by a wash at pH 6.0. The L-asparaginase was eluted by a wash at pH 6.8 (linear flow rate 95 cm h-1) and was substantially pure, only requiring polishing steps to be suitable for use as a parenteral agent. The purity of the protein was complemented by a 92% recovery of active enzyme from this cation-exchange matrix.

Construction of expression systems for Escherichia coli asparaginase II and two-step purification of the recombinant enzyme from periplasmic extracts

Isoenzyme II of Escherichia coli L-asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) is among the few enzymes of major therapeutic importance, being used in the treatment of acute lymphoblastic leukemia. We have constructed several inducible expression systems that overproduce asparaginase II from recombinant plasmids. The most efficient of these systems consists of plasmid pTWE1, a derivative of pT7-7, and an ansB- strain of E. coli, CU1783. These cells produce and secrete amounts of asparaginase II that account for 10-15% of the total cellular protein. Most of the active recombinant enzyme can be released from the periplasmic space by a simple osmotic shock procedure. From the resulting material homogeneous asparaginase II was obtained by a two-step procedure. Overall yields of purified asparaginase were 10-15 mg asparaginase II per liter of E. coli culture. The recombinant enzyme appeared identical to conventionally purified preparations.

Purification and properties of an L-asparaginase from Cylindrocarpon obtusisporum MB-10

An L-asparaginase producing mesophilic fungus Cylindrocarpon obtusisporum MB-10 was isolated from soil. The constitutive intracellular L-asparaginase from the organism was purified. The enzyme after 65-fold purification with an overall yield of 11% and specific activity of 100 unit.mg-1 seemed to be homogeneous in native, SDS-PAGE and thin layer isoelectric focusing gel. The apparent Mr of the enzyme was 216,000, and it constituted four identical subunits. The pI of the enzyme was 5.5. It was a conjugate protein with 37.3% (w/w) carbohydrate. The enzyme was stable to storage at -20 degrees C and to repeated freezing and thawing. The L-asparaginase from the organism was very much specific for L-asparagine and did not hydrolyze D-asparagine and L-glutamine. The pH and temperature optima for the enzyme activity were 7.4 and 37 degrees C, respectively. The Km of the L-asparaginase was found to be 1 x 10(-3)M. Metal ions, such as Zn2+, Fe2+, Cu2+, Hg2+ and Ni2+ potentially inhibited the enzyme activity, while metal chelators like EDTA, CN-, cysteine, etc., enhanced the activity indicating that the enzyme was not a metalloprotein. Its activity was also enhanced in the presence of reduced glutathione but not with dithiothreitol and 2-mercaptoethanol. Differential inhibition of the enzyme activity was observed with iodoacetamide and p-chloromercuribenzoate, thus indicating possible involvement of free-SH group in the enzyme catalysis.

Characterization and partial purification of L-asparaginase from Corynebacterium glutamicum

A high L-asparaginase (L-asparagine amidohydrolase: EC 3.5.1.1) activity was found under conditions of lysine overproduction in cultures of Corynebacterium glutamicum. L-Asparaginase was purified 98-fold by protamine sulphate precipitation. DEAE-Sephacel anion exchange, ammonium sulphate precipitation and Sephacryl S-200 gel filtration. The asparaginase protein was subjected to PAGE under non-denaturing conditions, identified by an in situ reaction and eluted from the gel in an active form. The estimated Mr from gel filtration and SDS-PAGE was 80,000. The L-asparaginase activity was inhibited by the L-asparagine analogue 5-diazo-4-oxo-L-norvaline. Neither D-asparagine nor L-glutamine was a substrate for the enzyme. L-Asparaginase was produced constitutively: its role may be that of an overflow enzyme, converting excess asparagine into aspartic acid, the direct precursor of lysine and threonine.

L-asparaginase from Erwinia carotovora. An improved recovery and purification process using affinity chromatography

A large-scale process was developed to purify L-asparaginase from submerged cultures of Erwinia carotovora. Cells from 880 L of fermentation broth were harvested and washed using a plate and frame type filter press. A cellular acetone powder was prepared from the washed cells by suspending the cells twice in acetone and the residual acetone was removed by washing the acetone powder in the filter press with 10 mM phosphate buffer (pH 7.0). The cellular acetone powder was extracted with 10 mM borate buffer at pH 9.5. The enzyme-rich borate extract was recovered by filtration and clarified by an in-line bag filter. The filtrate was adjusted to pH 7.5 and filtered through a 1-micron bag filter precoated with Celite and then through a 0.22-micron cartridge filter. The cell-free extract, containing 21 x 10(6) IU of enzyme and 448 g of total protein, was applied to an L-asparagine Sepharose 6 Fast Flow affinity column (9 L) using a bag filter loaded with Cell Debris Remover as an in-line prefilter. The affinity gel was prepared by coupling L-Asn at pH 9.0 to epoxy-activated Sepharose 6 Fast Flow beads. A total of 14 x 10(6) IU of enzyme (35 g protein) was eluted at pH 9.0 in 10.5 L. The eluted enzyme was determined to be greater than 90% pure using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The total process time from whole broth to affinity column elution was 68 h and the enzyme yield was 38%. This improved process for the 880 L fermentation broth produced a cell-free extract of high specific activity, shortened the process time, increased the column capacity, and yielded a product with high purity.

In vitro alterations of L-asparaginase activity of Tetrahymena pyriformis by lipids

A membrane-bound L-asparaginase (EC 3.5.1.1) of Tetrahymena pyriformis was purified to homogeneity. The purified enzyme is a lipoprotein, since it is inactivated by phospholipase C and its activity is restored by the addition of naturally occurring lipids, such as phosphatidylcholine, triolein and oleyl acetate. The relative effectiveness of a variety of phospholipids, free saturated and unsaturated fatty acids, or neutral lipids, such as esters of fatty acids and glycerides, with respect to the activation of purified L-asparaginase is compared. Enzyme activity is reconstituted in the presence of lipids and evidence for the formation of an enzyme-phospholipid complex is presented. The data of this report suggest that L-asparaginase may have a requirement for lipids that reconstitute a physiological hydrophobic environment, similar to the one existing in vivo.

Asparaginase II of Saccharomyces cerevisiae. Characterization of the ASP3 gene

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

Purification and properties of a membrane-bound L-asparaginase of Tetrahymena pyriformis

L-Asparaginase activity reaches maximal values at the stationary phase of growth of Tetrahymena pyriformis and fluctuates upon the growth conditions and the composition of the medium. Most of the L-asparaginase activity (80%) is associated with the endoplasmic reticulum, and the remaining with the pellicles. Detergents either alone or in combination with NaCl up to 0.5 M concentration failed to solubilize L-asparaginase. Solubilization can be accomplished by means of either the chaotropic agents KSCN and NaClO4, or 0.1 M sodium phosphate buffer pH 8.0, following pretreatment of the particulates with 2% w/v Triton X100. L-Asparaginase has been purified to near homogeneity by hydrophobic and gel filtration chromatography. The native enzyme has a relative molecular weight of 230,000. It is a multiple subunit enzyme, with subunit size of 39,000. Its isoelectric point is at pH 6.8. It acts optimally at pH 8.6 with a Km of 2.2 mM. It does not hydrolyse L-glutamine and its reaction is inhibited competitively by D-aspartic acid and D-asparagine as well as by L-asparagine analogues with substituents at the beta position.

Large-scale recovery and purification of L-asparaginase from Erwinia carotovora

A large-scale process was developed to purify gram quantities of a therapeutic enzyme, L-asparaginase, from submerged cultures of Erwinia carotovora. Cells were harvested from 150 L of fermentation broth and washed. A cellular acetone powder was prepared and extracted with pH 9.5 borate buffer. After continuous centrifugation and filtration to remove cell debris, the acetone powder extract was adjusted to pH 7.7 and adsorbed onto a 16-L CM-Sepharose Fast Flow column, with a precolumn packed with Cell Debris Remover. The enzyme was desorbed from the catin-exchange column at pH 9.0 and further purified with an affinity column of L-asparagine Sepharose CL-4B. After dialysis-concentration to remove buffer salt, the enzyme was depyrogenated, formulated, sterile filled, and lyophilized as a single-dose final product. The final-product evaluation included analysis of the content of protein, sodium chloride, glycine, sodium, glucose hydrate, phosphate, and endotoxin, as well as reconstitution, potency, pH, specific activity, uniformity of fill, and sterility. The product was further subjected to visual examination, sodium dodecyl sulfate polyacrylamide gel electrophoresis, native gel electrophoresis, isoelectric focusing, amino acid analysis, N-terminal sequencing, peptide mapping, and immunological comparison.

A specific L-asparaginase from Thermus aquaticus

The L-asparaginase from an extreme thermophile, Thermus aquaticus strain T351, was highly substrate- and stereospecific, with no activity against glutamine or D-asparagine. It had a high Km of 8.6 mM. In these aspects it closely resembled the corresponding enzymes from thermophilic bacteria. The enzyme had a molecular weight of 80,000, an isoelectric point of 4.6, and a pH optimum of 9.5. It showed some substrate inhibition above 20 mM asparagine and was also inhibited by L-aspartic acid, D- and L-lysine (Ki of 5.2 and 1.25 mM, respectively), and D- and L-serine. The half-life of the enzyme at 85 degrees C was 40 min. The Arrhenius plot showed a change in slope at 55 degrees C.

The purification and some properties of a stereospecific D-asparaginase from an extremely thermophilic bacterium, Thermus aquaticus

A specific D-asparaginase was isolated and crystallized from Thermus aquaticus strain T351. It is present in larger amounts than the L-asparaginase. The enzyme has a molecular weight of 60 000, an isoelectric point of 4.8 and a Km of 2 mM. It has 6 disulphide bonds/molecule, and a histidine residue at the active site. It is inhibited by keto acids and by high salt concentrations.

Isolation and characterization of a Chlamydomonas L-asparaginase

An L-asparaginase (EC 3.5.1.1) specific for L-asparagine has been purified from a marine Chlamydomonas species, the first such enzyme to be purified from a microalga. The purified enzyme (mol.wt. 275 000) possessed a Km for asparagine of 1.34 x 10(-4) M and showed limited antitumour activity in an antilymphoma assay in vivo. Properties of the enzyme are contrasted with those of asparaginases from prokaryotic and eukaryotic sources.

[Glutamin(asparagin)ase from Pseudomonas aurantiaca BKMB-548]

A method for isolation of glutamin (asparagin) ase from Pseudomonas aurantiaca BKMB-548 has been developed. The enzyme preparation is homogeneous during polyacrylamide gel electrophoresis (pH 7.5 and 7.0) with SDS. The pH-optima of the enzyme thermal stability and of the glutaminase activity are equal to 6.0-8.0. At higher pH values the asparaginase activity increases within the pH range of 4-9. The amino acid composition of glutamin(asparagin)ase has been determined.

Tumor inhibitory and non-tumor inhibitory L-asparaginases from Pseudomonas geniculata

Two enzymes that catalyze the hydrolysis of l-asparagine have been isolated from extracts of Pseudomonas geniculata. After initial salt fractionation, the enzymes were separated by chromatography on diethylaminoethyl-Sephadex and purified to homogeneity by gel filtration, ion-exchange chromatography, and preparative polyacrylamide electrophoresis. The enzymes differ markedly in physicochemical properties. One enzyme, termed asparaginase A, has a molecular weight of approximately 96,000 whereas the other, termed asparaginase AG, has a molecular weight of approximately 135,000. Both enzymes are tetrameric. The asparaginase A shows activity only with l-asparagine as substrate, whereas the asparaginase AG hydrolyzes l-asparagine and l-glutamine at approximately equal rates and it is also active with d-asparagine and d-glutamine as substrates. The asparaginase A was found to be devoid of antitumor activity in mice, whereas the asparaginase AG was effective in increasing the mean survival times of both C3H mice carrying the asparagine-requiring Gardner 6C3HED tumor line and Swiss mice bearing the glutamine-requiring Ehrlich ascites tumor line. These differences in antitumor activity were related to differences in the K(m) values for l-asparagine for the two enzymes. The asparaginase A has a K(m) value of 1 x 10(-3) M for this substrate whereas the corresponding value for the AG enzyme is 1.5 x 10(-5) M. Thus the concentration of asparagine necessary for maximal activity of the asparaginase A is very high compared with that of the normal plasma level of asparagine, which is approximately 50 muM.