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)

It has been demonstrated that the activity of asparaginase A from Ps. fluorescens AG is completely inhibited by 10(-4) M p-chloromercurybenzoate and by 70-85% by Zn2+, Ca2+ and Cu2+ (2.10(-2) M). Iodoacetate, iodoacetamide, N-ethylimide of maleic acid and 5,5'-dithiobis-(2-nitrobenzoic acid) do not decrease the enzyme activity. Dithiothreitol and beta-mercaptoethanol reactivate the enzyme. L-asparagine, the substrate of asparaginase, protects the enzyme in a large degree against the inhibitory action of p-chloromercurybenzoate. p-chloromercurybenzoate induces a sharp increase in the asparaginase inactivation rate at acidic (6.5--5.5) and alkaline (7.5-8.5) values of pH. The enzyme modification by p-chloromercurybenzoate does not change the Km value for L-asparagine, but decreases Vmax. Thus it may be assumed, that asparaginase from Ps. fluorescens AG contains sulfhydryl groups essential for the enzyme activity.
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PMID:[Sulfhydryl groups of L-asparaginase A from Pseudomonas fluorescens AG]. 1 36

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

The concentration dependence of the rate of hydrolysis of L-asparagine by Escherichia coli L-asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) has been measured over the range pH 4.5 to pH 9.1 by a direct spectrophotometric assay at 220 nm and by a coupled assay utilizing glutamate dehydrogenase to detect the ammonia produced. The velocity of the hydrolysis reaction at saturating levels of substrate is independent of pH over this interval. The plot of V/km over the same interval is bell-shaped, being dependent on pKa values of 6.58 and 8.69. The higher pKa is attributed to the amino group of asparagine. The lower pKa is associated with the enzyme active site and is probably due to an imidazole group.
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PMID:pH dependence of the kinetic parameters of L-asparaginase. 2 62

In this study, L-Asparaginase has been bound to collagen heterografts derived from carotid bovine arteries. The immobilization procedure utilizes both non-covalent and covalent interactions to fix the enzyme. Binding of the enzyme to the graft material was shown to the pH dependent, with optimum binding occurring at pH 6.0 and pH 8.5. Amidohydrolysis by the bound enzyme exhibited zero-order kinetic behavior at substrate saturating conditions. Total apparent asparaginase activity expressed by the grafts as a function of the number of repeated in vitro assay trials demonstrated that over a span of 3 months of intermittent storage and use, the enzyme-grafts retained as much as 62% of their initial activities. Implantation of 4 asparaginase-collagen grafts in various locations of the thoracic and abdominal aorta resulting in prolonged reductions of plasma asparagine levels in 3 of the 4 implants. Presence of plasma asparaginase was checked in one of the four implants and determined to be less than 2 X 10(-4) I.U./ml. Removal of grafts from 3 of the 4 animal subjects showed reductions in the apparent asparaginase activity expressed by the grafts of 7 to 70 percent after in vivo contact times which varied from 6 to 15 days.
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PMID:Preliminary studies with L-asparaginase bound to implantable bovine collagen heterografts: a potential long-term, sustained dosage, antitumor enzyme therapy system. 2 73

The formation of beta-aspartyl-glycine from asparagine and glycine was demonstrated in the supernatant of rat kidney. The enzyme involved in this process was partially purified. Based on the properties of the enzyme reaction and the coincidence of purification rates of this activity and asparaginase, it can be speculated that the enzyme is a kind of asparaginase. Examination of the preference for beta-aspartyl donors and acceptors showed that asparagine and glycine were the preferred donor and acceptor, respectively. beta-Aspartyl dipeptides also transferred their aspartyl residues to amino acids. Amino acids other than glycine also accepted the aspartyl moiety from the donors.
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PMID:Partial purification and characterization of an enzyme involved in the formation of beta-aspartyl dipeptides in rat kidney. 3 71

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.
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PMID:Tumor inhibitory and non-tumor inhibitory L-asparaginases from Pseudomonas geniculata. 3 47

L-Asparagine synthesis in Saccharomyces cerevisiae is performed by a glutamine-dependent asparagine synthetase of the type found in higher organisms. Auxotrophy for asparagine has been obtained in two classes of mutants. In class I, asparagine synthetase activity is cancelled. These mutants combine two mutations, asnA- and asnB-. Neither asnA- nor asnB- mutation alone leads to total auxotrophy. Partial auxotrophy as well as a strong decrease in enzyme activity result from asnA- mutation. No change is detectable in cells with the asnB- mutationalone. This, and Jones' report [J. Bacteriol. 134, 200-207 (1978)] of auxotrophy resulting from the combination of two mutations, are strong supports for asparagine synthesis being an unusual biosynthetic operation. In class II, auxotrophy results from a single mutation which leads to a modification of the efficiency of the asparaginyl-tRNA synthetase (asnRS- mutation). This auxotrophy is cancelled if asparaginase I activity (the only one present in sigma 1278b wild type) is cancelled by casnI- mutation. This latter mutation allows an increase in the asparagine pool which is able to compensate for the asparaginyl-tRNA synthetase partial defect of the asnRS- mutant.
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PMID:Synthesis and activation of asparagine in asparagine auxotrophs of Saccharomyces cerevisiae. 3 16

1. The mouse Gardner lymphoma 6C3HED was grown in ascites fluid in a form sensitive to the action of L-asparaginase (line 1), in another form which was resistant to L-asparaginase (line 2) and in a third form with partial sensitivity to L-asparaginase (line 3). 2. The L-asparaginyl-tRNA synthetase activities of extracts of the tumour cells, cultured both in the mouse and in vitro, were determined. Two of the lines, 1 and 3, in early passage numbers, showed a derepression mechanism involving L-asparagine. Mutation occurred with these lines resulting in the L-asparaginyl-tRNA synthetase activity of all the tumour cell lines being the same. 3. Cells of line 1 had low L-asparagine synthetase activity, which was unchanged by altering the supply of L-asparagine in vitro. Cells of lines 2 and 3 exhibited L-asparagine synthetase activities, which changed with the supply of L-asparagine. 4. It is not certain that L-asparagine synthetase activity of L-asparaginase-sensitive cells is controlled by L-asparaginyl-tRNA acting as a corepressor.
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PMID:L-asparaginyl-tRNA synthetase and L-asparagine synthetase activities of L-asparaginase-sensitive and -resistant forms of the mouse Gardner lymphoma 6C3HED. 3 36

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

Production of L-asparaginase by two soil isolates, identified as S. karnatakensis and S. venezuelae, was investigated under different environmental and nutritional conditions. The presence of carbon sources, other than starch, in the growth medium or amino acids, other than L-asparagine-inhibited the enzyme biosynthesis. L-aspartic inhibited growth and enzyme production, due to a feedback mechanism, and/or lowering the pH value. Both organisms were stimulated to produce more enzyme with increasing concentrations of starch and L-asparagine, however, the optimum starch and L-asparagine concentration depended on the tolerance of the organism to low and high pH, respectively. Aeration stimulated growth, but not enzyme production, and both organisms produced more enzyme in static cultures than in shaken cultures.
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PMID:Production of L-asparaginase by Streptomyces karnatakensis and Streptomyces venezuelae. 4 13


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