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

---

Query: EC:3.5.1.1 (asparaginase)
2,695 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The denaturation and reconstitution of Erwinia carotovora and Escherichia coli L-asparaginases has been followed by optical rotatory dispersion, circular dichroism and analytical ultracentrifugation. Denaturation in urea results in dissociation of the native enzyme (mol. wt. 140 000 approx.) to produce unfolded subunits (mol. wt. 35 000 approx.); the Erwinia L-asparaginase subunits can be refolded by dilution or dialysis in alkaline conditions, pH 10.5, without aggregation to the active tetramer, to give a rather unstable solution of a monomer possibly in equilibrium with dimer. These alkaline-reconstituted subunits undergo a conformational change to a more ordered state in the presence of sodium dodecylsulphate, similar to those produced by the action of sodium dodecylsulphate on the native enzyme. If the denatured subunits are reconstituted in the pH range 5.0-7.5, the enzymically active tetramer is reformed in up to 80% yield, depending upon the conditions of temperature and concentration. Kinetic data for these various transitions suggest that dissociation is a rate-limiting step while conformational changes of the polypeptide chains are relatively much more rapid. The possible significance of these different rates of change to therapeutic considerations is discussed.
...
PMID:Comparative study on conformational stability and subunit interactions of two bacterial asparaginases. 23 38

Electrolyte disturbances in leukemia can be the result of the disease process or drug therapy. One group of electrolyte abnormalities is related to the stage of the leukemic process. Included in this group are newly diagnosed patients who may show elevated serum potassium, phosphorus, and magnesium--a result of their release from malignant cells after cytotoxic therapy or their accumulation due to urate nephropathy. Patients in remission usually have normal serum electrolyte concentrations, but acute leukemia patients during relapse may have hypokalemia, hypophosphatemia, and hypomagnesemia. This imbalance may be related to cellular uptake of these electrolytes in the presence of inadequate dietary intake. Other factors contributing to electrolyte derangements, and related to the leukemic process, include hyponatremia and hypochloremia secondary to the SIADH, hypokalemia in acute monocytic or acute myelomonocytic leukemia due to lysozyme-induced tubular damage, hypercalcemia possibly secondary to leukemic infiltration of bone or parathyroid glands (with PTH release), or production of a PTH-like substance by leukemic cells. Nonspecific factors related to the disease process which may aggravate the electrolyte imbalance include gastrointestinal loss through nausea, vomiting, and malnutrition. The drug-related electrolyte abnormalities include cyclophosphamide- and vincristine-induced SIADH; decreased serum sodium, chloride, potassium, and calcium concentrations as a result of polymyxin B nephrotoxicity; hypokalemia and hypomagnesemia secondary to amphotericin B; hypocalcemia, hypophosphatemia, and hyperphosphaturia due to L-asparaginase-induced hypoparathyroidism; hypokalemia due to a nonreabsorbable anion effect of antibiotics in the distal tubule or changes in membrane ionic transport of all cells by large doses of antibiotics. Electrolyte disturbance in leukemia thus have a multifactorial pathogenesis which can best be delineated according to the stage of the leukemic process and the drugs being used. Recognition of the cause or causes in a particular patient is essential for an effective approach to management. This review emphasizes the need for routine measurement of serum electrolytes during all phases of the leukemic process.
...
PMID:Electrolyte and acid-base disturbances in the management of leukemia. 26 90

Reductive coupling with sodium cyanoborhydride has been used with lactose and N-acetylneuraminyl lactose to prepare glycosylated Escherichia coli L-asparaginase. A substantial degree of modification can be achieved without significant loss of enzyme activity. The lactosylated enzyme shows increased thermal stability and resistance to proteolytic cleavage and is cleared more rapidly from the plasma of mice, compared to native asparaginase. The effect on clearance varies directly with the degree of lactosylation. Asparaginase modified with N-acetylneuraminyl lactose, in contrast, with approximately 13.6 mol of N-acetylneuraminyl lactose/mol of enzyme, is cleared more slowly, with a t 1/2 that is approximately twice that of the native enzyme.
...
PMID:Glycosylation of Escherichia coli L-asparaginase. 33 66

Earlier work has shown that 5-diazo-4-oxo-L-norvaline (DONV) irreversibly inactivates the L-asparaginase from E. coli by formation of a covalent bond in the region of the active site. Model compounds have been prepared to study this acid-labile covalent bond tentatively assigned to a serine or possibly a threonine residue in a decapeptide isolated from 14C-DONV-inactivated enzyme. Appropriately blocked DONV was found to alkylate methanol, and the hydroxyl function of blocked serine or threonine in the presence of boron trifluoride. The labile beta-ketoethers thus formed were reduced to the more stable beta-hydroxyethers. Facile lactonization of these 5-substituted-4-hydroxy-L-norvalines was observed. The diastereoisomers of both the lactonized and open forms of 5-methoxy-4-hydroxy-L-norvaline and related 4-hydroxy-L-2-amino acids of similar length were distinguishable on the amino acid analyzer. The beta-hydroxyethers derived from serine and threonine were hydrolyzed with acid and yielded the expected cleavage products. When the beta-ketoether was reduced by sodium borohydride prior to deblocking, in addition to the beta-hydroxyether, N-blocked amino alcohols were also formed, yielding a complex mixture of products.
...
PMID:Synthesis of model compounds relevant to the active-site-directed inactivation of L-asparaginase by 5-diazo-4-oxo-L-norvaline. 38 21

Acinetobactor glutaminase-asparaginase was treated with [6-14C]diazo-5-oxonorleucine, reduced with sodium borohydride, and cleaved with cyanogen bromide. Radioactivity was present only in a 96-residue-N-terminal peptide which eluted as the second peptide peak on Sephadex G-50. Radioactivity was released with the threonine in position 12 during automatic sequencing of this peptide. The amino acid sequence of a 60-residue tn-terminal segment and a 16-residue C-terminal segment of this peptide was determined. Pseudomonas 7 A glutaminase-asparaginase was treated with [6-14C]diazo-5-oxonorleucine and reduced with sodium borohydride. Radioactivity was released with the threonine in residue 20 during automatic sequencing of the whole enzyme. Analysis of 26 N-terminal residues showed that an 8-residue segment containing the radioactive threonine was identical with that in Acinetobacter glutaminase-asparaginase and in Escherichia coli asparaginase. Additional identical residues were noted in the N-terminal regions of these enzymes.
...
PMID:Amino acid sequence of the diazooxonorleucine binding site of Acinetobacter and Pseudomonas 7A glutaminase--asparaginase enzymes. 61 99

Effect of urea on the activity of serum L-asparaginase in outbred guinea pigs (Hartley) was examined for comparison between heat-resistant and heat-sensitive types. The heat-resistant serum L-asparaginase was much more stable to urea-treatment than the heat-sensitive serum enzyme, and the urea-inactivation of the serum enzyme was protected by Na+ or K+. Liver L-asparaginase of the guinea pig, in which the serum enzyme was resistant to heat, was also resistant to heat, and vice versa, although liver enzyme was much more sensitive to heat than serum enzyme. The heat inactivation of liver enzyme was also protected by Na+. Similar results were also demonstrated on purified serum L-asparaginase, although the amino acid compositions between the two purified enzyme preparations were slightly different. When the animal having heat-resistant serum L-asparaginase were crossed with each other, serum enzyme of the resultant progenies was also resistant to heat, and vice versa. The serum enzyme of two inbred strains (JY-1, Hartley/F) was thermostable and the enzyme of the other (Strain 2, Strain 13) was thermolabile.
...
PMID:Effect of strain differences on heat-susceptibility of L-asparaginase in the guinea pig. 71 34

Homogenization of guinea pig liver in isotonic sucrose solution followed by the separation of the subcellular fractions by differential centrifugation releases the liver L-asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) activity into the supernatant fraction. Electron micrographs of the liver L-asparaginase-antibody complexes, precipitated from the clear supernatant phase by addition of L-asparaginase-specific antiserum, show membrane-liek structures and some amorphous material. The attachment of L-asparaginase to the membrane-like structures is indicated by the ferritin-labeled antibody technique. The immunoprecipitates possess low activities of 5'-nucleotidase, alkaline phosphodiesterase I, NADPH cytochrome c reductase, glucose-6-phosphatase, and acid phosphatase. This observation suggests that L-asparaginase found in the liver supernatant fraction is associated with cytomembrane components. Analysis of guinae pig serum L-asparaginase-antibody complexes is polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate gives three distinct protein bands. These bands correspond to heavy and light chains of rabbit immunoglobulins and the L-asparaginase subunits. Analysis of the liver L-asparaginase-antibody complexes by the above procedure shows similar but more diffuse protein bands.
...
PMID:Evidence for the association of L-asparaginase with cytomembrane components in the guinea pig liver soluble fraction. 81 93

The fluorescence lifetimes and relative quantum yields of several derivatives of tyrosine are reported. The quenching of the fluorescence of these compounds by phosphate, caesium and iodide ions has been investigated; the encounter rate constants, calculated from the quenching parameters and lifetimes, show a clear dependence on the charges borne by the quenchers and fluorophores. The ratio of the Stern-Volmer constants of iodide and caesium, ions of similar size, defines an electrostatic parameter sensitive to the charge of the fluorophore which can be evaluated without knowledge of the fluorescent lifetimes. The mean of the encounter rate constants for caesium and iodide ions defines a rate constant which is largely charge-independent and is used to establish a steric parameter. The two parameters are used to investigate the tyrosine environment in bovine ribonuclease A (EC 3.1.4.23) and Erwinia carotovora L-asparaginase (EC 3.5.1.1). The quantum yield of L-asparaginase (0.12) is very high for a class A protein and may be associated with the absence of disulphide bridges. There was no evidence for more than one type of tyrosine residue from the quenching experiments with either enzyme, an observation which is attributed to efficient energy transfer amongst tyrosine residues. At pH values close to the isoelectric points of the enzymes the electrostatic parameter suggests that the environment of the quenchable tyrosines in L-asparaginase is somewhat more positive than in ribonuclease. In 1% sodium dodecyl sulphate the tyrosine environment of L-asparaginase becomes markedly negative as expected. The steric parameter indicates a lower accessibility of the tyrosine residues in L-asparaginase than in ribonuclease; an illustrative calculation is provided linking the steric parameter with the number of exposed tyrosine residues by taking into account the greater collision frequency of the larger protein molecules and the encounter distance for quenching determined from charge effects on the quenching of the model compounds. The calculation suggests that three tyrosyl residues are accessible in ribonuclease, in good agreement with other studies, but in L-asparaginase the number increases from 0.4 at pH 5.73 to 0.8 at pH 9.16 suggesting a loosening of the enzyme structure at high pH.
...
PMID:An investigation of the electronic and steric environments of tyrosyl residues in ribonuclease A and Erwinia carotovora L-asparaginase through fluorescence quenching by caesium, iodide and phosphate ions. 98 70

A method potentially capable of enhancing the effectiveness of therapeutic enzymes such as L-asparaginase was investigated. The method was suggested by the following properties that have been observed for lectins injected into tissues: (1) six lectins with differing specificities were retained near the site of injection in the feet of mice 10 to 100 times longer than several non-lectin proteins. Prolonged retention of 125I-labelled concanavalin A was also observed in other normal and malignant mouse tissues. (2) The retention of 125I-labelled concanavalin A was not affected by prior immunization against concanavalin A. (3) Electrophoresis of tissue extracts on sodium dodecyl sulfate-poly-acrylamide gels followed by radioautography indicated that the 125I-labelled concanavalin A retained in the tissue remained as intact in form as prior to injection. Since the therapeutic efficacy of many enzymes may be enhanced by localization at the intended site of action, in principle it should be possible to enhance the effectiveness of therapeutic enzymes by combining the tissue-localizing properties of a lectin with therapeutic effectiveness of the enzyme. A conjugate of E. coli L-asparaginase and concanavalin A has been prepared by covalent cross-linking with glutaraldehyde and has been shown to be retained in mouse tissue 90 times longer than the free enzyme. However, it is completely ineffective in the treatment of the L-asparaginase-sensitive lymphosarcoma 6C3HED in C3H/HeJ mice. The ineffectiveness of the conjugated enzyme may be associated with the interiorization of the conjugate by the cells of the tumor.
...
PMID:Effect of localization of L-asparaginase as the concanavalin A conjugate on anti-tumor activity. 103 89

Purified L-asparaginase from Serratia marcescens had an apparent-weight average molecular weight of 171,000 to 180,000 as determined by electrophoresis on polyacrylamide gels and by sedimentation equilibrium at low speed in an analytical ultracentrifuge. A subunit molecular weight of 31,500 +/- 1,500 was estimated for the enzyme after treatment with sodium dodecyl sulfate and urea and electrophoresis on polyacrylamide gels; a similar value was obtained by high-speed sedimentation equilibrium in the presence of guanidine hydrochloride. Our data indicate that the Serratia enzyme could have five or six subunits of 32,000 daltons, compared to four subunits of 32,000 daltons in the Escherichia coli enzyme. The Serratia L-asparaginase also appears to be a larger molecule than the enzyme from Erwinia carotovora, Proteus vulgaris, Acinetobacter glutaminasificans, and Alcaligenes eutrophus. The Serratia enzyme, like that from E. caratovora, was more resistant than the E. coli enzyme to dissociation by sodium dodecyl sulfate. This resistance could be due to the finding that the Serratia enzyme had a relatively high hydrophobicity, similar to the enzyme from E. caratovora, when compared with the hydrophobicity of the E. coli enzyme. The isoelectric point of the Serratia enzyme was approximately 5.2. The influence of certain physical characteristics of the enzyme on the biological properties is discussed.
...
PMID:Physical properties of L-asparaginase from Serratia marcescens. 110 30


1 2 3 4 5 6 Next >>

---