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Z G Evstigneeva

Publications and source records attributed to Z G Evstigneeva.

12 recordsLinked to original sources
PubMed1979

[Purification and physico-chemical properties of glutamine synthetase from pea chloroplasts].

A highly purified, practically homogeneous glutamine synthetase was isolated from pea leaf chloroplasts. The enzyme purity was assayed by polyacrylamide gel electrophoresis and analytical ultracentrifugation. The sedimentation coefficient is 16,3S. The sedimentation equilibrium analysis showed that the molecular weight of the enzyme is equal to 480 000. The minimal molecular weights of the enzyme as calculated from the data of polyacrylamide gel electrophoresis in the presence of SDS and the amino acid analysis were found to be 62 000 and 60 000, respectively. The enzyme contains a large amount of dicarboxylic and sulfur-containing amino-acids. The N-terminal amino acid is glycine. The isoelectric point for the enzyme lies within the pH range of 4,2-4-4.

Amino Acids↗
PubMed1978

[Irreversible inactivation of Chlorella glutamine synthetase by urea].

The effect of urea on Chlorella glutamine synthetase (E. C. 6.3.1.2) activity and tertiary structure is investigated. Urea is found to inhibit the activity of glutamine synthetase, the inhibitory effect being independent on the time. The enzyme molecule relax and changes its affinity to ammonium under the effect of urea at concentrations of 1.0-4.0 M. Higher concentrations of urea (5,0 M and more) produce a dissociation of the enzyme molecule into monomers without any intermediate forms. Monomers do not possess any synthetase and transferase activities. Substrates and cofactors do not protect the enzyme from the effect of urea and do not stimulate the emzyme reactivation and reaggregation after its dissotiation. The data obtained are discussed from the viewpoint of the regulation of Chlorella glutamine synthetase activity in vivo.

Animals↗
PubMed1978

[Presence of SH-groups and histidine in the active site of Chlorella glutamine synthetase].

The presence of two cysteine residues per each six monomers comprising the oligomer of Chlorella glutamine synthetase (E.C.6.3.1.2) is demonstrated using homogenous enzyme preparation. p-Chloromercuribenzoate (p-CMB) is found to inhibit glutamine synthetase activity, the degree of inhibition depending on the inhibitor concentration. The following enzyme reactivation by dithiotreitol (10(-2) M) was observed only when the enzyme was inactivated with 10(-5) M p-CMB under 15 min. preincubation. Preincubation of the enzyme with 10(-4) M p-CMB for 45 min. did not result in its reactivation. Gel filtration of glutamine synthetase treated with 10(-4) M p-CMB has revealed the dissociation of the enzyme into inactive monomers. Incubation of glutamine synthetase with p-CMB at various pH values, incubation after pre-treatment with urea and experiments with HgCl2 indicate the presence of free and masked inside the globula SH-groups in the enzyme molecule. Competitive character of the enzyme inhibition with p-CMB with respect to ATP indicates that SH-groups of the active site participate in the ATP binding, probably, as Mg-ATP or Mn-ATP complexes. Data on the estimation of ionization constant of glutamate-binding group and experiments on the effect of histidine photooxidation on the enzyme activity indicate the presence of histidine residue in the enzyme active site, which participates in glutamate binding.

Adenosine Triphosphate↗
PubMed1977

[Purification, properties and quaternary structure of glutamine synthetase from Chlorella].

A highly purified preparation of glutamine synthetase from chlorella grown on a medium containing nitrate as a sole source of nitrogen, was isolated and characterized by disc-electrophoresis and analytical ultracentrifugation. The N-terminal amino acid of glutamine synthetase is glycine. The molecular weight of glutamine synthetase is 32.000; its activity in the presence of Mg2+ was 150 mkmol o-phosphate per min per mg protein. The molecular weight of subunits of the enzyme, equal to 53.000 was determined by disc-electrophoresis in polyacrylamide gel in the presence of sodium dodecyl sulfate. Electron microscopy of negatively contrasted enzyme preparations revealed 6 subunits in the enzyme molecule, arranged in a point symmetry group 32.

Chlorella↗
PubMed1977

[Regulation of glutamine metabolism in Chlorella pyrenoidosa. Regulation of glutamine synthetase activity by adenylic system components].

A decrease of glutamine synthetase (E. C. 6.3.1.2.) activity was observed under the assimilation of ammonium nitrogen in Chlorella. At the same time a decrease of ATP content in Chlorella cells took place. The ATP content was 7-fold decreased, while ADP and AMP contents were 4-fold and 3-fold increased respectively, after 15 min. of Chlorella incubation on "ammonium" medium. Further incubation for 45 min, resulted in gradual increase of ATP content and in decrease of ADP and AMP contents. The value of energy charge in ammonium assimilating Chlorella cells sharply decreased for first 15 min. of incubation and then it normalized gradually. The experiments with glutamine synthetase preparation, isolated from ammonium assimilating cells, have shown that ADP and AMP are strong inhibitors of the enzyme in the presence of Mg2+, and only ADP produces the inhibitory effect in the presence of Mn2+. No enzyme reactivation was observed after the transfer of ammonium assimilating cells into nitrogen-free medium or nitrate medium, the enzyme activity increasing at the expense of enzyme protein synthesis denovo.

Adenine Nucleotides↗
PubMed1976

[Regulation of glutamine metabolism in Chlorella pyrenoidosa. Mechanisms of regulating the activity of glutamine synthetase during ammonia assimilation].

Glutamine synthetase (GS) (E.C.6.3.1.2) activity in Chlorella cells decreased when NH4+ was added to nitrogen-free growth medium. This GS inactivation had such a rate, that it could not be due to the repression of enzyme synthesis: the GS activity decreased by 20% within 5 minutes of NH4+ assimilation. Glutamine content in cell increased in 2.5 times for this period. In vitro experiments have shown that glutamine is a strong inhibitor of GS from Chlorella grown in the presence of NO3-, and in a less degree--an inhibitor of GS from cells grown in ammonium-containing medium. The data obtained are negative with respect to possible mechanisms of GS activity regulation via adenylation and ATP-dependent destruction of glutamine synthetase.

Ammonia↗
PubMed1976

[Glutamine metabolism regulation in Chlorella pyrenoidosa. Regulation of Chlorella glutamine synthetase activity by amino acids].

Effect of glutamine and its metabolites (amino acids) on Chlorella glutamine synthetase (GS) (E.C.6.3.1.2) in the presence of Mg or Mn was studied. Purified GS preparation was used, isolated from Chlorella grown in the presence of NH as a sole nitrogen source. Glutamate, aspartate, alanine and glycine inhibit GS activity in the presence of both Mg and Mn. Tryptophane and valine (up to 15 mM) activate GS in the presence of Mn. Tryptophane inhibits GS in the system with Mg. Sinergistic inhibition was observed under the combined effect of amino acids on GS in the presence of Mn and aspartate or alanine. The change of GS activity observed is supposed to be due to the inhibitory effect of glutamine and amino acids studied, since the glutamine content is increased (in 2.5 times for 5 min) and that of alanine and dicarbonic amino acids (for the following 15 min) under NH assimilation in Chlorella cells.

Amino Acids↗
PubMedDate not supplied

[Glutamine synthetase immobilization].

Highly purified glutamine synthetase has been isolated from Chlorella and immobilized on BrCN-sepharose. Its residual activity was 25-35%. Immobilized glutamine synthetase showed far greater thermal stability than glutamine synthetase in solution. During immobilization pH optimum of the enzyme was shifted towards the alkaline area, maximum rate of the reaction was reduced and KM remained unaltered.

Chlorella↗