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

Cultural and nutritional requirements for a maximum synthesis of 1-asparaginase by staphylococci were determined. The best production of the enzyme was found in the stationary phase of growth of a batch culture. The highest 1-asparaginase yield was obtained when the culture were aerated during an exponential phase of growth and further incubated in the stationary phase. Optimum pH for the enzyme production was 7.5. Glucose inhibited the enzyme formation. Maximum yield of 1-asparaginase was obtained when casein hydrolysate and yeast extract were supplied as carbon and nitrogen sources. Repression by 1-asparagine and 1-aspartic acid was absent.
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PMID:Factors influencing L-asparaginase production by staphylococci. 1 83

A Chlamydomonas species isolated from a marine environment possesses an L-asparaginase, an enzyme not yet reported in the microalgae. This enzyme enabled the organism to grow as well with asparagine as sole nitrogen source as with inorganic nitrogen sources (NO3-, NH4+). Only the amide nitrogen was used for growth since growth did not occur on aspartate and aspartate accumulated in the media when cells were either grown on asparagine or during short-term incubations with L-[U-14C]asparagine. Cells grown on NO3-, NH4+, or L-asparagine in batch culture possessed equivalent asparaginase activities. However, nitrogen-limited cells possessed four times the activity of cells grown with sufficient nitrogen for normal growth, regardless of the possessed the lowest activity per cell, while lag phase and stationary phase cells possessed greater activity. The enzyme behaved like a periplasmic space enzyme since (1) breaking the cells did not release into solution more activity than was shown by whole cells and (2) whole cells converted L-[U-14C]asparagine to [14C]aspartate with little intracellular accumulation of radioactivity. Cell-free preparations of the enzyme possessed a Km value for asparagine of 1.1 x 10-4 M, with no glutaminase activity.
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PMID:Asparagine metabolism and asparaginase activity in a euryhaline Chlamydomonas species. 4 71

Five actinomycete isolates (all belonged to the genus Streptomyces), capable of producing detectable amounts of L-asparaginase, were isolated from the soil of Kuwait after enrichment. The three most potent enzyme producers were identified as different strains of Streptomyces collinus. Factors affecting enzyme production by the strongest strain were examined. Synthetic media with asparagine as a nitrogen source stimulated more enzyme production than natural media. Starch and asparagine at final concentrations of 1 and 0.8%, respectively, were optimum for enzyme production. An initial pH of 8.5 for the growth medium and an incubation temperature of 28-30 degrees C in a static culture for 6 days stimulated enzyme production by the examined strain of Streptomyces collinus.
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PMID:L-asparaginase-producing Streptomyces from the soil of Kuwait. 4 99

During recent studies conducted with suspensions of three strains of Saccharomyces cerevisiae, it was observed that ammonia was rapidly liberated when L-asparagine was added to the medium. Subsequent investigation has revealed that these strains of S. cerevisiae have an externally active asparaginase as well as an internally active one. The appearance of the external asparaginase is stimulated by nitrogen starvation, requires an available energy source, and is prevented by cycloheximide. The internal enzyme appears to be constitutive. The external activity is relatively insensitive to para-hydroxymercuribenzoate inhibition, whereas the internal activity is highly inhibited by this compound.
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PMID:L-Asparaginase of Saccharomyces cerevisiae: an extracellular Enzyme. 23 36

The formation of the high-affinity (Km equal to 0.2 muM) L-glutamine transport system of Escherichia coli strain 7 (Lin) appears to be subject to the same major control as the glutamine synthetase (EC 6.3.1.2) of this gram-negative organism. Culture of cells under nitrogen-limited conditions provides maximum derepression of both the glutamine synthetase and the glutamine transport system. Nutritional conditions providing a rich supply of ammonium salts or available sources of nitrogen, i.e., conditions which repress the formation of glutamine synthetase, provide three- and 20-fold repression, respectively, of the glutamine transport system. Culture of cells with glutamine supplements of 2 mM does not increase the repression of high-affinity glutamine transport system beyond the level observed in the absence of glutamine. A second kinetically distinct low-affinity component of glutamine. A second kinetically distinct low-affinity component of glutamine uptake is observed in cells cultured with a glutamine-depleted nutrient broth. This second component is associated with the appearance of glutaminase A (EC 3.5.1.2) and asparaginase I (EC 3.5.1.1), a periplasmic enzyme. Parallel changes were observed in the levels of the high-affinity glutamine transport system and the glutamine synthetase when cells were cultured with the carbon sources: glucose, glycerol, or succinate.
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PMID:Regulation of Glutamine Transport in Escherichia coli. 23 38

The effect of 18 amino acids and 7 organic acids on the production of L-asparaginase EC-2 by a strain of Escherichia coli in a chemically defined medium was investigated under moderate aeration. All the amino acids and some of the organic acids stimulated the enzyme production. The specific activity without stimulants was about 0.16 nkat per mg dry weight, with stimulants it lay between 1 and 6 nkat per mg dry weight but with L-leucine and L-methionine the values were 12 nkat and 17 nkat per mg, respectively. When two organic or amino acids were added simultaneously at concentrations that were suboptimal for stimulation, the stimulating effects were cumulative in most cases. When cells were grown under conditions approaching anaerobiosis, the specific activity reached, even in the absence of stimulants, values as high as 5 nkat per mg; under these conditions, a further substantial increase in specific activity was only caused by L-leucine and L-methionine. Stimulating effects of DL-lactate and of some amino acids were also found in other strains of Escherichia coli. The ability to grow on a medium with L-asparagine as the sole source of both nitrogen and carbon was found in two strains; growth took place even when there was no measurable activity of L-asparaginase EC-2.
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PMID:Stimulation of L-asparaginase production in Escherichia coli by organic and amino acids. 32 7

The cistron that codes for L-asparaginase I in Saccharomyces cerevisiae (aspl) is not genetically linked to either of the cistrons coding for expression of asparaginase II (asp2 and asp3). Cells containing different combinations of theses enzymes grow at different rates in media in which L-asparagine or D-asparagine is the only source of nitrogen for cell replication. Cells lacking L-asparaginase I but possessing asparaginase II grow more rapidly in medium containing D-asparagine as a nitrogen source than cells containing both enzymes, even though D-asparagine is not a substrate of L-asparaginase I. These results indicate that L-asparaginase I and asparaginase II interact in some way to regulate the utilization of asparagine as a nitrogen source for cell growth.
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PMID:Genetic and physiological relationships between L-asparaginase I and asparaginase II in Saccharomyces cerevisiae. 32 21

Saccharomyces cerevisiae X2180-1A synthesizes two forms of asparaginase: L-asparaginase I, an internal constitutive enzyme, and asparaginase II, an external enzyme which is secreted in response to nitrogen starvation. The two enzymes are biochemically and genetically distinct. The structural gene for asparaginase I (asp 1) is closely linked to the trp 4 gene on chromosome IV. The gene controlling the synthesis of asparaginase II is not linked to either the trp 4 or asp 1 genes. The rate of biosynthesis of asparaginase II is unaltered in yeast strains carrying the structural gene mutation for asparaginase I. Asparaginase II has been purified approximately 300-fold from crude extracts of Saccharomyces by heat and pH treatment, ethanol fractionation, ammonium sulfate fractionation followed by Sephadex G-25 chromatography, and DEAE-cellulose chromatography. Multiple activity peaks were obtained which, upon gas chromatographic analysis, exhibit varying mannose to protein ratios. Asparaginase I has been purified approximately 100-fold from crude extracts of Saccharomyces by protamine sulfate treatment, ammonium sulfate fractionation, gel permeation chromatography, and DEAE-cellulose chromatography. No carbohydrate component was observed upon gas chromatographic analysis. Comparative kinetic and analytic studies show the two enzymes have little in common except their ability to hydrolyze L-asparagine to L-aspartic acid and ammonia.
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PMID:Characterization of two forms of asparaginase in Saccharomyces cerevisiae. 34 21

The activity of deamidases of L-glutamine and L-asparagine of Pseudomonas boreopolis 526 was found to depend on the conditions of cultivation. The activity of L-glutaminase-asparaginase II (EC 3.5.1.38) decreased with an increase of the specific growth rate in the conditions of periodic cultivation and increased in the conditions of continuous cultivation. The activity of this enzyme was manifested mainly in the conditions of continuous cultivation at a rate of 0.1--0.2 hr-1 and a final nitrogen concentration of 0.006--0.025 g per litre of the medium. If the concentration of nitrogen was increased in these conditions, biosynthesis of L-glutaminase-asparaginase I was stimulated while the activity of L-glutaminase-asparaginase II was not detected at all.
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PMID:[L-glutaminase-asparaginase biosynthesis by a Pseudomonas boreopolis culture dependent on cultivation conditions]. 67 79


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