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N A Andreeva

Publications and source records attributed to N A Andreeva.

At least 37 records · Page 2Linked to original sources
PubMed1999

Hydrolysis of tripolyphosphate by purified exopolyphosphatase from Saccharomyces cerevisiae cytosol: kinetic model.

The kinetics of hydrolysis of tripolyphosphate by purified exopolyphosphatase from Saccharomyces cerevisiae cytosol has been studied in the presence of Mg2+. Two kinetic models suggesting the formation of complexes of tripolyphosphate and the enzyme with Mg2+ are compared. Both models suggest that only enzyme--substrate complexes containing Mg2+ and tripolyphosphate simultaneously are able to hydrolyze the tripolyphosphate. The first model suggests that the enzyme is able to bind to Mg2+ independently from substrate binding. The second model does not consider this possibility, but suggests that both complexes containing tripolyphosphate and Mg2+ in proportion 1:1 and 1:2 can serve as the reaction substrates. The description of the experimental data by both models is essentially the same. The complex containing tripolyphosphate and Mg2+ in proportion 1:1 is optimal for the enzyme activity, the complex containing tripolyphosphate and Mg2+ in proportion 1:2 being hydrolyzed at a lower rate.

Acid Anhydride Hydrolases↗
PubMed1998

The lack of extracellular Na+ exacerbates Ca2+-dependent damage of cultured cerebellar granule cells.

Rhodamine 123 staining, light and electron microscopy were used to evaluate the ultrastructural and functional state of cultured cerebellar granule cells after short treatment with the solution where NaCl was substituted by sucrose (sucrose balance salt medium, SBSM). Cell exposure to SBSM for 20 min resulted in the fact that mitochondria in the neurons lost their ability to sequester rhodamine 123. This effect could be prevented by: (i) non-competitive N-methyl-D-aspartate (NMDA) receptor channel blocker, 10(-5) M MK-801; (ii) a competitive specific antagonist of NMDA glutamate receptors, 0.25 x 10(-3) M D,L-2-amino-7-phosphonoheptanoate (APH); (iii) 10(-3) M cobalt chloride; (iv) removal of Ca2+ from the medium. Low Na+ in the Ca2+-containing medium caused considerable mitochondrial swelling in granule cells. However, the same treatment in the absence of calcium ions in the medium abolished the deleterious effect of SBSM on the neuronal mitochondrial structure and functions. It is suggested that (i) the exposure of cultured cerebellar granule cells to SBSM leads to a release of endogenous glutamate from cells; (ii) Ca2+ ions potentially de-energizing neuronal mitochondria enter the neuron preferentially through the NMDA channels rather than through the Na+/Ca2+ exchanger; (iii) mitochondrial swelling in granule cells is highly Ca2+-dependent; (iv) cellular overload with sodium ions can activate mitochondrial Na+/Ca2+ exchanger and thus prevent permeability transition pore opening in mitochondria.

Animals↗
PubMed1998

Purification and properties of exopolyphosphatase isolated from Saccharomyces cerevisiae vacuoles.

An exopolyphosphatase (polyPase) with a specific activity of 60 U/mg protein has been purified from the vacuolar sap of Saccharomyces cerevisiae. The molecular mass of the intact enzyme was found to be 245 kDa. It is highly specific towards high-molecular polyphosphates (polyP). The activity with polyP9 is 24% of that with polyP208. The apparent Km for polyP15 and polyP208 hydrolysis is 93 and 2.4 microM, respectively. The enzyme is slightly active with polyP3 and adenosine-5'-tetraphosphate, but does not hydrolyze pyrophosphate, ATP, GTP and p-nitrophenylphosphate. It is stimulated by divalent metal cations. Co2+, the best activator, stimulates it 6-fold. Antibodies that inhibit the cell envelope and cytosol polyPases of S. cerevisiae have no effect on the vacuolar polyPase. The vacuolar polyPase differs from other yeast polyPases in molecular mass, substrate specificity and effects of activators.

Acid Anhydride Hydrolases↗
PubMed1998

Inhibition of glutamate-induced intensification of free radical reactions by gangliosides: possible role in their protective effect in rat cerebellar granule cells and brain synaptosomes.

The neurotoxic effect of exposure of rat cerebellar granule cells to glutamate (100 microM) is to a large extent prevented by incubation of neurons not only with micromolar, but even with nanomolar concentrations of gangliosides GM1, GD1b, and GT1b. GM1 was also shown to decrease significantly the per cent of dead neurons in culture after induction of lipid peroxidation. Exposure to glutamate was found to cause a significant decrease of the activity of Na+, K+-ATP-ase in rat brain cortex synaptosomes, but superoxide dismutase, alpha-tocopherol, or 10-100 nM GM1 practically prevented its action. Other data showing the ability of gangliosides to inhibit the intensification of free radical reactions by glutamate (based on the estimation of methemoglobin formation, SH group content, etc.) have been obtained. The results suggest that gangliosides are able to decrease the glutamate-induced activation of free radical reactions in nerve cells. This effect appears to contribute to their protective action against glutamate neurotoxicity.

Animals↗
PubMed1997

Comparison of exopolyphosphatases of different yeast cell compartments.

Purified cell-envelope polyphosphatase as well as polyphoshatase activities of cytosol and isolated vacuoles, of nuclei and mitochondria of the yeast Saccharomyces cerevisiae were compared. The polyphosphatases of cell envelope and cytosol are similar, the polyphosphatases of nuclei, vacuoles and mitochondria differ in their kinetic properties, substrate specificity, requirements in divalent cations and in some effector actions both from these and from each other.

Acid Anhydride Hydrolases↗
PubMed1997

Adenosine-5'-tetraphosphate and guanosine-5'-tetraphosphate: new substrates of the cytosolic exopolyphosphatase of the yeast Saccharomyces cerevisiae.

A cytosolic preparation of Saccharomyces cerevisiae is capable of hydrolyzing adenosine-5'-tetraphosphate and guanosine-5'-tetraphosphate with activities which are 1.5-2 times greater than that with polyP15. The apparent K(m) values for hydrolysis of adenosine-5'-tetraphosphate and guanosine-5'-tetraphosphate are 100 and 80 microM, respectively. A comparative study of inhibitors shows that these activities are inherent characteristics of these exopolyphosphatases.

Acid Anhydride Hydrolases↗
PubMed1996

[Purification and characteristics of Saccharomyces cerevisiae cytosol polyphosphatase].

The polyphosphatase with specific activity of 283 units/mg was purified 3450-fold to homogeneity with 3.8% yield from cytosol of Saccharomyces cerevisiae yeast. Polyphosphatase is monomeric 40 kD protein. The enzyme hydrolyzes polyphosphates of various chain length including tripolyphosphate but ATP, pyrophosphate, and p-nitrophenyl phosphate are not the substrates. Enzyme activity is maximal at 50 degrees C and pH 6.5-8.5. Several cations of bivalent metals stimulated the enzyme activity 8-66-fold (Co2+ > Mn2+ > Mg2+ > Zn2+ > Fe2+). The enzyme is inactive in the presence of Ca2+ or Cu2+. Heparin, antibodies against cell-envelope polyphosphatase, and Cu2+ or Zn2+ in the presence of Mg2+ are potent inhibitors of cytosolic polyphosphatase. Cytosolic polyphosphatase is similar to purified cell-envelope polyphosphatase but differs in some properties from nuclear, vacuolar, and mitochondrial polyphosphatase of the very same yeast.

Acid Anhydride Hydrolases↗
PubMed1995

[Organelle specificity of yeast cell polyphosphatases].

The properties of purified cell envelope polyphosphatase, polyphosphatase activities of vacuoles and cytosol fractions of the Saccharomyces cerevisiae yeast have been compared. The whole body of evidence presently available suggest that each of the compartments under study is equipped with its own polyphosphatase which differs from polyphosphatases of other organelles. It is proposed that the organelle specificity of yeast polyphosphatases may reflect the endosymbiotic origin of eucaryotic cells.

Acid Anhydride Hydrolases↗
PubMed1995

[Immunoenzyme analysis of polyphosphatases from various compartments of yeast cells].

Antibodies against purified polyphosphatase from the Saccharomyces cerevisiae cell envelope inhibited the activity of this enzyme and the polyphosphatase activity of the cytosol, being without any effect on vacuolar and nuclear polyphosphatase activities from the same yeast species cells. Using immunoblotting, it has been shown that it is the 40 kDa polypeptide that binds to these antibodies in preparations of cell envelope and cytosolic polyphosphatase. The molecular mass of these polyphosphatases determined by other methods was almost indentical. The 72 and 40 kDa polypeptides bind to these antibodies in isolated vacuoles, while the 64 and 32 kDa polypeptides--in isolated nuclei.

Acid Anhydride Hydrolases↗
PubMed1994

[Characteristics of polyphosphatase activity of Saccharomyces cerevisiae cytosol].

The cytosol fraction purified from cellular organelles was obtained from S. cerevisiae yeast cells. This cytosolic fraction contained a polyphosphatase activity comprising nearly 65% of such in the protoplast homogenate. The pH optimum of this activity was 6.5-7.5. Bivalent metal cations stimulated the polyphosphatase activity 9-14-fold in the following order: Zn2+ > Co2+ > Mg2+, Mn2+. Fe2+, Cu2+ and Ca2+ ions inhibited this activity at all concentrations used. The cytosolic polyphosphatase was effectively inhibited by molybdate and heparin. Heparin was effective only in the presence of Mg2+, Mn2+ and Co2+ but had no effect in the presence of Zn2+. Heparin inhibited polyphosphatase competitively. The polyphosphatase activity was the same with poly (P)9-poly (P)208. On poly (P)9, poly (P)15 and poly (P)208 the Km(app) values were equal to 19, 11, 1.2 microM, respectively. The molecular mass of cytosolic polyphosphatase determined by gel filtration on Sephacryl S-300 was 50 kDa.

Acid Anhydride Hydrolases↗
PubMed1993

Purification and characterization of highly active and stable polyphosphatase from Saccharomyces cerevisiae cell envelope.

Saccharomyces cerevisiae cell envelope polyphosphatase was isolated in highly active and stable form by extraction from cells with zwittergent TM-314 followed by chromatography of the extract on phosphocellulose and QAE-Sephadex in the presence of 5 mM-MgCl2, 0.5 mM-EDTA and 0.1% Triton X-100. The enzyme possessed a specific activity of 220 U/mg and after 30 days retained 87% of its activity at -20 degrees C. Polyphosphatase molecular mass was determined to be about 40 kDa by gel filtration and polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme hydrolysed polyphosphates with various chain lengths (n = 3-208), had low activity for GTP and did not split pyrophosphate, ATP and p-nitrophenylphosphate. On polyphosphates with chain lengths n = 3, 9 and 208, Km values were 1.7 x 10(-4), 1.5 x 10(-5) and 8.8 x 10(-7) M respectively. Polyphosphatase was most active and stable at pH 6.0-8.0. The enzyme showed maximal activity at 50 degrees C. The time of half inactivation of polyphosphatase at 40, 45 and 50 degrees C was 45, 10 and 3 min, respectively. In the absence of divalent cations and also with Ca2+ or Cu2+, the enzyme showed practically no activity. The ability of divalent cations to activate polyphosphatase was reduced in the following order: Co2+ > Mg2+ > Mn2+ > Fe2+ > Zn2+. Polyphosphatase was completely inhibited by 1 mM-ammonium molybdate and 50 microM-Zn2+ or Cu2+ (in the presence of Mg2+).

Acid Anhydride Hydrolases↗
PubMed1993

[Characteristics of polyphosphatase activity of vacuoles in Saccharomyces cerevisiae cells].

Vacuoles of the Saccharomyces cerevisiae yeast possess a polyphosphatase activity which differs from other known vacuolar phosphohydrolase activities by pH-optimum, sensitivity towards inhibitors and distribution between the tonoplast and vacuolar sap. The polyphosphatase activity is inhibited by EDTA, molybdate, ortho-vanadate and fluoride. Nearly 77% of this activity is located in the vacuolar sap, while 25%--in the tonoplast fraction. Both the soluble and membrane-bound polyphosphatase activities are maximal at pH 6.8-7.2. Bivalent metal cations stimulate this activity in the following order: Zn2+ > Mg2+ > Co2+ > Mn2+. Other ions (Fe2+, Cu2+, Ca2+) inhibit this activity at all concentrations tested. The polyphosphatase activity of both the vacuolar sap and the tonoplast increases 2.4-and 2-fold, respectively, with an increase in the degree of substrate polymerization--from n = 3 to n = 208.

Cations, Divalent↗
PubMed1991

[Vitamin E decreases the neurocytotoxic action of kainic acid in a cerebellar neuron culture].

Using primary cultures of cerebellar granule cells from 4-6-day old Wistar rats we showed the protective effect of vitamin E against kainate-induced neurotoxicity. The preincubation of 7-8-day old cultures with 5 x 10(-4) M alpha-tocopherol solution significantly (on 10-20%) reduces the number of damaged granule cells. As vitamin E takes part in stabilization of membrane lipids the data presented allows us to suggest that one of the possible mechanisms of neuronal injury includes lipid oxidation of the neuronal membranes which leads to additional influx of Ca2+ and results in neuronal death.

Animals↗
PubMed1990

[The use of a polyethyleneimine substrate for culturing dissociated cells of the central nervous system].

A new method of preparation of polyethylenimin substrate for cultivation of dissociated cells from different parts of the central nervous system is presented. The alcohol solution of polyethylenimin used for this substrate is easily prepared, needs no sterilization and can be stored unlimitedly. The substrate provides a good attachment, growth and differentiation of neurons and glial cells and possesses all the advantages of more expensive polyaminoacid substrates (polylysine, polyornithine). Our substrate is highly adhesive, displays good optical properties and no artefacts after histological and histochemical treatment.

Animals↗