Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.1 (asparaginase)
 2,695 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of nutritional variables on the processing of exogenous precursors into RNA was examined. General nutritional deprivation, or asparagine depletion, led to significant changes in the absolute pool sizes, especially of ATP, UTP and CTP. Fluctuations were found depending on the elapsed time after the nutritional perturbations occurred, and the cell density of the cultures. Depletion of the medium by 28 h of growth, or 1 h of guinea pig asparaginase action, led to considerable inhibition of the conversion of exogenous uridine to CTP by the cells. A series of experiments indicated that in 6C3HED lymphoma cells the uridine nucleotide pool which provided the immediate precursors to RNA (denoted UTP-NA) behaves as a small compartment in rapid equilibrium with exogenously supplied nucleosides. The resemblance to the compartmentation model described by Plagemann (Plagemann, P.G.W. (1972) J. Cell Biol. 52, 131-146 and (1971) J. Cell. Physiol. 77, 241-258) for rat hepatoma cells was close. The UTP-NA pool of the 6C3HED cells constitutes no more than 5% of the cellular UTP pool and is relatively slow in equilibrating with the general cell pool. Correction of the rates of incorporation of isotope into RNA by using some function of the whole cell UTP specific activity to normalize the pool effects, was shown to be invalid.
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PMID:Nutritional effects on precursor uptake and compartmentalization of intracellular pools in relation to RNA synthesis. 117 50

Methods are presented for separating the three IgM heavy chain sialoglycopeptides associated with asparagines 170, 332, and 395. The core glycopeptide units containing the disaccharide fucosyl-N-acetylglucosamine were obtained through the use of an endo-beta-N-acetylglucosamindase from Diplococcus pneumoniae, following exoglycosidase treatment of the sialoglycopeptides. In addition to the core glycopeptides, high yields of a tetrasaccharide, (Man)3GlcNAc, were obtained. The fucose in the core disaccharide is glycosidically linked to the 6-O position of the N-acetylglucosamine residue in Asn-GlcNAc. This core unit is resistant to glycosyl asparaginase, but becomes susceptible to hydrolysis on removal of the fucosyl residue by a purified hen oviduct alpha-L-fucosidase. The core sequence of the immunoglobulin M sialoglycopeptides appears to be similar to that of most other asparagine-linked oligosaccharides in consisting of a basic unit composed of beta-D-Man-(1 leads to 4)beta-D-GlcNAc(1 leads to 4)beta-D-GlcNAc(1 leads to 4), but with L fucose linked alpha-(1 leads to 6) to the proximal GlcNAc. The two nonreducing terminal ends of (Man)3GlcNAc are linked to beta-D-Man by alpha-(1 leads to 3) and alpha(1 leads to 6) bonds, respectively.
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PMID:The isolation and structure of the core oligosaccharide sequences of IgM. 120 Dec 77

New methods for the determination of L-asparagine and arginine are described. Solutions containing L-asparagine were pumped through an asparaginase tube, which catalyzed the hydrolysis of L-asparagine to L-aspartis acid and ammonium ion. For L-arginine determination, solutions containing L-arginine were pumped through an arginase-urease tube. This dual enzyme tube catalyzed the conversion of L-arginine to L-ornithine, carbon dioxide, and ammonium ion. The ammonium ion concentrations in the effluent of the enzyme tubes were determined quantitatively by an ammounin-ion-selective electrode. The potentiometric response of the electrode was directly proportional to the logarithm of the concentration of L-asparagine and L-arginine in the range of 0.1-50 mM. An equation relating the electrode response and the substrate concentration is derived.
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PMID:Reagentless determination of L-asparagine and L-arginine via the combined use of immobilized enzymes and an ion-selective electrode. 125 83

L-Asparaginase has long been used in the treatment of acute lymphoblastic leukemia or malignant lymphoma in childhood. To determine cell type specific sensitivity to this drug, the L-asparaginase-mediated inhibition of blastogenesis of human peripheral T or B lymphocytes was compared. The rate of incorporation of [3H]-thymidine into the DNA of either T lymphocytes due to phytohemagglutinin (PHA) or B lymphocytes due to Staphylococcus aureus Cowan I (SAC) was measured by the addition of Escherichia coli L-asparaginase in the medium. The blastogenic response of either T or B lymphocytes was also determined in medium depleted of exogenous asparagine and/or glutamine, both of which are hydrolyzed by this enzyme. The in vitro blastogenesis of either human T lymphocytes due to PHA or B lymphocytes due to SAC was inhibited by the inclusion of asparaginase in the medium. The deprivation of exogenous asparagine did not have any inhibitory effect on the blastogenic response of both T and B lymphocytes to each mitogen. On the other hand, the glutamine concentration in the culture medium provided a critical influence on the proliferative response of T and B lymphocytes. The rate of incorporation of [3H]-thymidine into DNA was increased markedly as the concentration of glutamine was increased from 2(-7)-2 mmol/l. It is concluded that the mechanism of inhibition of PHA- or SAC-stimulated lymphocyte blastogenesis by L-asparaginase is not asparagine deprivation but glutamine deprivation. Glutamine, which is the most abundant amino acid, is thought to have an important role in the immune response of lymphocytes.
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PMID:The inhibition of lymphocyte blastogenesis by asparaginase: critical role of glutamine in both T and B lymphocyte transformation. 128 1

L-asparaginase is an enzyme that inhibits protein synthesis by the depletion of sources of L-asparagine, which is necessary for transformed lymphoid cells to proliferate. L-asparaginase is used in the treatment of childhood acute lymphoblastic leukemia. A problem with L-asparaginase therapy is the immunogenicity of the enzyme and the development of anaphylactic reactions. Canine lymphoma is a predominantly B-cell tumor with widespread disease; without treatment, dogs with lymphoma usually survive 1-2 months. Canine lymphoma will respond to L-asparaginase therapy. A randomized double-blind study evaluated a polyethylene glycol (PEG) conjugate L-asparaginase combined with chemotherapy (vincristine, cyclophosphamide, doxorubicin, and prednisone). Thirty-five dogs were randomized to the PEG L-asparaginase group, and 34 dogs were randomized to the native L-asparaginase group. Thirty dogs (85.7%) achieved a complete remission (CR) with a median time to relapse of 217 days, and 32 (94.1%) dogs in the native L-asparaginase group achieved a CR with a median time to relapse of 214 days (P greater than 0.05). The asparaginase was well tolerated in both groups. Two dogs in the native L-asparaginase group had severe allergic reactions, and one dog in the PEG asparaginase group had a generalized urticarial reaction after repeated injections. This study indicates that PEG L-asparaginase has equal therapeutic efficacy to native L-asparaginase.
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PMID:Evaluation of L-asparaginase: polyethylene glycol conjugate versus native L-asparaginase combined with chemotherapy. A randomized double-blind study in canine lymphoma. 152 54

Human glycoasparaginase (N4-(beta-N-acetyl-D-glucosaminyl)-L-asparaginase, EC 3.5.1.26) hydrolyzes a series of compounds that contain L-asparagine residue with free alpha-amino and alpha-carboxyl groups. Substrates include high mannose and complex type glycoasparagines as well as those that lack the di-N-acetylchitobiose moiety, L-aspartic acid beta-methyl ester and L-aspartic acid beta-hydroxamate. The enzyme is inactive toward L-asparagine and L-glutamine and glycoasparagines containing substituted alpha-amino and/or alpha-carboxyl groups. In the presence of the acyl acceptor hydroxylamine, glycoasparaginase catalyzes the synthesis of L-aspartic acid beta-hydroxamate from aspartyl-glucosamine, L-aspartic acid beta-methyl ester, and L-aspartic acid. 13C NMR studies using 18O-labeled L-aspartic acid demonstrate that glycoasparaginase catalyzes an oxygen exchange between water and the carboxyl group at C-4 of L-aspartic acid. These results indicate that glycoasparaginase reacts as an exo-hydrolase toward the L-asparagine moiety of the substrates and the free alpha-amino and alpha-carboxyl groups are required for the enzyme reaction. The results are consistent with an L-asparaginase-like reaction pathway which involves a beta-aspartyl enzyme intermediate. Since glycoasparaginase is active toward a series of structurally different glycoasparagines, we suggest the revised systematic name of N4-(beta-glycosyl)-L-asparaginase for the enzyme.
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PMID:Substrate specificity and reaction mechanism of human glycoasparaginase. The N-glycosidic linkage of various glycoasparagines is cleaved through a reaction mechanism similar to L-asparaginase. 155 92

Cell lines resistant to 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3- (2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) show a high degree of collateral sensitivity to L-asparaginase. The mechanism for this phenomenon was investigated by comparing the nutritional requirements and asparagine synthetase activity of the resistant sublines to those of parent cells. Nine ACNU-resistant sublines were isolated from rat glioma 9L cells after incubation with various concentrations of ACNU in Ham's F-12 medium. The 9L cells grew independently of asparagine, developing well in asparagine-deficient Dulbecco's modified Eagle's medium. In contrast, the growth rates of all nine ACNU-resistant sublines decreased under the same conditions and required the addition of 10(-4) M asparagine for maximum growth. Asparagine synthetase activity in the ACNU-resistant cells was much lower than in the 9L cells, suggesting that the requirement for asparagine in the resistant sublines was due to reduced activity of this enzyme. A growth-inhibition assay showed that the ACNU-resistant sublines were more sensitive to L-asparaginase than 9L cells by up to 2 x 10(5)-fold. These results suggest that L-asparaginase therapy has the potential to become a new approach for treating acquired ACNU resistance.
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PMID:Hypersensitivity of rat glioma sublines with acquired ACNU resistance to L-asparaginase. 168 27

Successful chemotherapeutic treatment of drug-responsive cancers can be compromised by the acquisition of drug resistance. Standard remission induction therapy for childhood acute lymphoblastic leukemia includes L-asparaginase, since the leukemic cells lack asparagine synthetase (AS) activity and require exogenous asparagine. We have used the Chinese hamster ovary cell line N3, which lacks AS activity, as a model to examine a novel mechanism involved in the development of drug resistance in acute lymphoblastic leukemia. Expression of AS in Chinese hamster ovary cells is associated with hypomethylation in the 5' region of the gene. Activation of AS in concert with hypomethylation occurs spontaneously at a frequency of about 10(-6); we have found that treatment with the hypomethylating drug 5-azacytidine induces a reversion frequency of 10(-2). To investigate the possibility that chemotherapeutic drugs induce similar changes, the asparagine auxotrophic cell line N3 was treated with the chemotherapeutic agents L-asparaginase, vincristine, and 1-beta-D-arabinofuranosylcytosine and with the mutagen ethyl methanesulfonate. Both L-asparaginase and ethyl methanesulfonate increased the frequency of reversion to asparagine prototrophy to about 10(-5), whereas vincristine and 1-beta-D-arabinofuranosylcytosine had no such effect. Asparagine prototrophy correlated with the demethylation of CpG sites in the 5' region of the AS gene and with the appearance of AS mRNA in revertants. In addition to the specific effect seen with the AS gene, L-asparaginase and ethyl methanesulfonate induced global reductions in methylation of up to 25 and 10%, respectively. The ability of chemotherapeutic drugs to inhibit DNA methylation and thereby activate previously silent genes may enable them to promote the aggressiveness of cancers in vivo, including the expression of drug resistance.
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PMID:Hypomethylation and reactivation of the asparagine synthetase gene induced by L-asparaginase and ethyl methanesulfonate. 170 43

Glutamine depletion strongly inhibits the replication of Rauscher murine leukaemia retrovirus (RLV) in vitro. Pseudomonas 7A glutaminase-asparaginase (PGA), capable of depleting glutamine and asparagine for prolonged periods, was used to determine the therapeutic effectiveness of glutamine depletion in mice infected with RLV or Friend virus. During PGA treatment of viraemic animals, serum reverse transcriptase activity fell to control levels and infected animals did not develop splenomegaly. The therapeutic results obtained with PGA compared favourably with those of azidothymidine given intraperitoneally at 30 mg/kg/day. Western blots performed on splenic tissue from control and treated animals indicated that glutamine depletion prevented readthrough of an amber codon at the gag-pol junction, stopping translation of viral mRNA at that point. Treatment of RLV-infected animals with PGA resulted in nearly a 200% increase in mean survival time even when therapy was initiated late in the course of the disease. To our knowledge, this is the first demonstration that a nutrient required for viral replication can be enzymically depleted in vivo to inhibit viral replication.
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PMID:Inhibition of mouse retroviral disease by bioactive glutaminase-asparaginase. 170 10

The ph optimum of purified staphylococcal L-asparaginase (EC 3.5.1.1) was found to be between 8.6 and 8.8. The temperature optimum was 30 degrees-32 degrees C and the highest reaction rate occurred at 30 degrees C. The KM of the enzyme calculated from Lineweaver-Burk plot was 3.71 x 10(-2) M. Besides L-asparaginase, the substrate specificity of enzyme was restricted to N-alpha-acetyl-L-asparagine. D-asparagine, L-aspartic acid and D-glutamic acid were competitive inhibitors. Hg2+ and Cu2+ cations strongly inhibited the enzyme while Na+ and K+ cations strongly stimulated activity. Two SH-groups could be detected after enzyme denaturation with guanidine.
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PMID:Staphylococcal L-asparaginase: enzyme kinetics. 172 15


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