Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

An L-asparaginase has been purified some 250-fold from extracts of Klebsiella aerogenes to near homogeneity. The enzyme has a molecular weight of 141,000 as measured by gel filtration and appears to consist of four subunits of molecular weight 37,000. The enzyme has high affinity for L-asparagine, with a Km below 10(-5) M, and hydrolyzes glutamine at a 20-fold lower rate, with a Km of 10(-3) M. Interestingly, the enzyme exhibits marked gamma-glutamyltransferase activity but comparatively little beta-aspartyl-transferase activity. A mutant strain lacking this asparaginase has been isolated and grows at 1/2 to 1/3 the rate of the parent strain when asparagine is provided in the medium as the sole source of nitrogen. This strain grows as well as the wild type when the medium is supplemented with histidine or ammonia. Glutamine synthetase activates the formation of L-asparaginase. Mutants lacking glutamine synthetase fail to produce the asparaginase, and mutants with a high constitutive level of glutamine synthetase also contain the asparaginase at a high level. Thus, the formation of asparaginase is regulated in parallel with that of other enzymes capable of supplying the cell with ammonia or glutamate, such as histidase and proline oxidase. Formation of the asparaginase does not require induction by asparaginase and is not subject to catabolite repression.
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PMID:L-Asparaginase of Klebsiella aerogenes. Activation of its synthesis by glutamine synthetase. 0 59

Crystalline glutaminase-asparaginase which is effective against solid as well as ascites tumors was prepared from soil isolate organism Pseudomonas 7A. This enzyme has a ration of Vmax for L-glutamine and L-asparagine of 2.0. The presence of glutamic acid in the growth medium is essential for optimal enzyme production and glucose inhibits the production of glutaminase-asparaginase. The purification procedure provides an overall yield of 40 to 45% from crude cell extract to homogeneous glutaminase-asparaginase and is adaptable to large scale production of the enzyme. The specific activity of homogeneous enzyme is 160 +/- 15 i.u./mg of protein and the E1% 280 is 9.8. No disulfide or sulfhydryl groups appear to be present on the enzyme. The isoelectric point of glutaminase-asparaginase by isoelectric focusing on ampholine polyacrylamide gel plates is 5.8. The Km values for L-glutamine and L-asparagine are 4.6 and 4.4 X 10(-6) M, respectively. The enzyme catalyzes the hydrolysis of the D isomers of glutamine and asparagine at 87 and 69% the rate of the respective L isomers. L-Glutamic acid gamma-monohydroxamate is hydrolyzed at approximately the same rate as L-glutamine. The enzyme is not inhibited by ethylenediaminetetraacetate (0.1 mM), L-glutamate (30 mM), or L-aspartate (30 mM). Ammonium sulfate (10 mM) inhibits the enzymatic activity. The plasma half-life of Pseudomonas 7A glutaminase-asparaginase if 13 hours in normal mice and 43 hours in mice infected with the lactate dehydrogenase-elevating virus.
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PMID:Purification and properties of a highly potent antitumor glutaminase-asparaginase from Pseudomonas 7Z. 0 41

The nutritional requirements and culture conditions affecting biosynthesis of L-asparaginase in a mutant of Escherichia coli HAP designated strain A-1 were studied. Asparaginase activity was increased by the addition of L-glutamic acid, L-glutamine, or commercial-grade monosodium glutamate. The rate of enzyme synthesis was dependent on the interaction between the pH of the culture and the amount of oxygen dissolved in the medium. A critical oxygen transfer rate essential for asparaginase formation was identified, and a fermentation procedure is described in which enzyme synthesis is controlled by aeration rate. Enhancement of L-asparaginase activity by monosodium glutamate was inhibited by the presence of glucose, culture pH, chloramphenicol, and oxygen dissolved in the fermentation medium.
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PMID:Effect of culture conditions on synthesis of L-asparaginase by Escherichia coli A-1. 1 9

Seven Mycobacterium strains were grown statically on salts-glycerol-asparagine (Sauton) or on salts-glucose-glutamate (Sym) media. At desired time of incubation, the bacteria were washed with water, disintegrated with powdered corundum and in resulting cell-free extracts L-asparaginase activity was determined by the Conway method. The majority of experiments were performed on M. phlei which exhibited considerable rise in L-asparaginase activity with increasing age of the culture. This change did not occur on Sym medium because of Zn2+, which proved to abolish the effect of the enzyme induction in vivo but did not inhibit the activity in vitro. Addition of rifampicin to Sauton culture media resulted in a low enzyme level. Exogenous asparagine and glycerol were not indispensable for the enzyme synthesis and could be replaced by glutamate and glucose, respectively.
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PMID:L-asparaginase activity of Mycobacterium phlei under various growth conditions. 24 89

Growing cells of Yersinia pseudotuberculosis, but not those of closely related Yersinia pestis, rapidly destroyed exogenous L-aspartic and L-glutamic acids, thus prompting a comparative study of dicarboxylic amino acid catabolism. Rates of amino acid metabolism by resting cells of both species were determined at pH 5.5, 7.0, and 8.5. Regardless of pH, Y. pseudotuberculosis destroyed L-glutamic acid, L-glutamine, L-aspartic acid, and L-asparagine at rates greater than those observed for Y. pestis. Although rates of proline degardation were similar, its metabolism by Y. pestis at pH 8.5 resulted in excretion of glutamic and aspartic acids. Similarly, Y. pestis excreted aspartic acid when incubated with L-glutamic acid (pH 8.5) or L-asparagine (pH 5.5, 7.0, and 8.5). Aspartase activity was not detected in extracts of 10 strains of Y. pestis but was present in all 11 isolates of Y. pseudotuberculosis. The latter contained significantly more glutaminase, asparaginase, and L-glutamate-oxalacetate transminase activity than did extracts of Y. pestis; specific activities of L-glutamate dehydrogenase and alpha-ketoglutarate dehydrogenase were similar. The observed differences in dicarboxylic amino acid metabolism are traceable to asparatase deficiency in Y. pestis and may account for the slow doubling time of this organism relative to Y. pseudotuberculosis.
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PMID:Consequences of aspartase deficiency in Yersinia pestis. 71 77

Acinetobacter glutaminase-asparaginase (AGA) and Escherichia coli asparaginase were compared for their effects on plasma and tissue levels of amino acids, ammonia, and glutamyl transferase activity in the mouse. Free asparagine was depleted similarly in plasma and tissues by both enzymes. AGA treatment produced partial depletion of glutamine concentrations in muscle, spleen, small intestine, and liver. Brain and kidney glutamine concentrations actually rose with treatment. Despite over 100-fold increase in plasma glutamate, only the kidney showed a substantial increase in free glutamate levels during AGA treatment. Glutamine biosynthesis measured by glutamyl transferase activity showed an appreciable increase only in the kidney. Ammonia levels in tissues and plasma rose 1.3- to 4.3-fold. In general, E. coli asparaginase treatment had much less effect on these measurements than did AGA. The changes in these levels are discussed in relation to sites of possible toxicity and antitumor effects.
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PMID:Effect of Acinetobacter glutaminase-asparaginase treatment on free amino acids in mouse tissues. 109 50

Escherichia coli asparaginase (Asnase) pretreatment of Asnase-sensitive L5178Y cells in vitro is thought to antagonize methotrexate (MTX) cytotoxicity through nonspecific inhibition of protein synthesis and MTX uptake. We have reexamined the mechanism of this interaction in view of recent data demonstrating the importance of MTX metabolism to polyglutamate derivatives (MTXPGs) in the cytotoxic effects of the antifolate. After a 3-hr exposure to 0.5 microM MTX, 67% of intracellular drug was in the form of MTXPGs containing a total of 2 to 5 glutamyl residues (MTX-Glu2-5), and cloning efficiency in drug-free medium was only 7% of untreated control. After a 3-hr pretreatment with E. coli Asnase (0.1 unit/ml), [3H]thymidine incorporation dropped by 29%, MTXPG formation during subsequent MTX exposure decreased by more than one-half (MTX-Glu2 unchanged; MTX-Glu3 and 4 decreased to 51.7 and 18.5% of levels achieved in cells not pretreated with Asnase; no MTX-Glu5 formed), and cloning efficiency increased to 71% of untreated control. This effect was not due to decreased MTX uptake into L5178Y cells or to decreased intracellular free L-glutamate or L-glutamine levels. A 3-hr exposure of L5178Y cells to media lacking L-isoleucine, an essential amino acid for cell growth, prior to MTX exposure inhibited [3H]thymidine incorporation by 37%, decreased subsequent MTXPG formation by 62%, and increased subsequent cloning in drug-free medium to control levels. Decreased MTXPG formation was responsible for the prevention of MTX cytotoxicity seen after both pretreatments. Unmetabolized MTX rapidly left L5178Y cells after removal of extracellular MTX. Consequently, lower levels of unbound intracellular drug, a prerequisite of drug activity, were maintained in pretreated than in control cells after passage in drug-free medium. Asnase pretreatment protects L5178Y cells from the cytotoxic effects of MTX, possibly through inhibition of cell growth which nonspecifically decreases MTXPG formation.
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PMID:Prevention of methotrexate cytotoxicity by asparaginase inhibition of methotrexate polyglutamate formation. 257 94

A rapid, reproducible HPLC method based on dansyl chloride derivatization has been developed for the determination of L-asparagine, L-aspartate, L-glutamine, and L-glutamate in mouse and human serum samples. This improved procedure has been designed for automation with an autoinjector system. Studies with mice bearing the sensitive and the asparaginase-resistant L5178Y leukemia show that this analytical method can be employed to monitor the effect of L-asparaginase on serum levels of these four amino acids. The method can be used to monitor serum amino acid levels in patients undergoing therapy with L-asparaginase.
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PMID:Serum amino acid levels in leukemic mice after L-asparaginase treatment. 337 8

In studies on kinetics of thermoinactivation of glutaminase (asparaginase) from Ps. arantiaca BKMB-548 at 50 degrees and pH 7.0 in presence or in absence of L-glutamate the enzyme inactivation was found to obey the first order equation. Both the glutaminase and asparaginase activities decreased at a similar rate. L-Glutamate stabilized the enzyme due to direct interaction with its molecule. Stability of the complex formed was evaluated quantitatively. L-Glutamate reacted apparently with a specific site on the surface of the enzyme molecule; Kdiss was 0.42 +/- 0.03 mM at pH 7.0 and 50 degrees. No cooperative effect was found. L-Aspartate protected the enzyme completely; stabilizing effects of L-cysteine, L-serine and glycine were similar to the effect of L-glutamate (94%, 84%, 83% and 82%, respectively). At the same time, glutarate, succinate, alpha-ketobutyrate, alpha-ketoglutarate, gamma-aminobutyrate and N-benzoyl glutamate did not exhibit the stabilization effect. The data obtained suggest that the high stabilizing effect might exhibit only the substances containing simultaneously free alpha-NH2 and alpha-COOH groups in a molecule, whereas presence of COOH groups at beta--or gamma-carbon atoms was not essential for the stabilizing effect.
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PMID:[Thermostabilization of glutamin(asparagin)ase from Pseudomonas aurantica BKMB-548]. 402 28

L-Asparaginase (EC 3.5.1.1) inhibited respiration in sensitive, but not resistant, lines of murine lymphoma 6C3HED. Glucose, in these tumor lines, was principally converted to lactate, and very little was oxidized in the citric acid cycle or hexose monophosphate shunt. The cells derived 70-80% of their respiratory CO(2) from glutamine or glutamate. Asparaginase had no effect on the pattern of glucose utilization. The differential effect on oxygen consumption may result from the absence of asparagine synthetase in sensitive cells. Respiration may be inhibited by accumulation of the aspartate, the product of glutamate oxidation. Resistant lymphoma cells remove aspartate by converting it to asparagine. Sensitive cells, which lack asparagine synthetase, cannot make asparagine.
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PMID:Glutamate oxidation of 6C3HED lymphoma: effects of L-asparaginase on sensitive and resistant lines. 453 Feb 80


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