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Biomedical subjects

N N Chernov

Publications and source records attributed to N N Chernov.

18 recordsLinked to original sources
PubMed2006

Changes in expression of genes encoding antioxidant enzymes, heme oxygenase-1, Bcl-2, and Bcl-xl and in level of reactive oxygen species in tumor cells resistant to doxorubicin.

The relationship between expression of genes encoding key antioxidant enzymes, heme oxygenase-1, Bcl-2, and Bcl-xl and change in production of reactive oxygen species (ROS) resulting from development of resistance of cancer cells K562, MCF-7, and SKOV-3 to the prooxidant chemotherapeutic agent doxorubicin (DOX) has been studied. Significant increase in mRNA level and activity of Mn-superoxide dismutase (Mn-SOD), catalase, and selenium-dependent glutathione peroxidase-1 (GPx-1) and reduced ROS level was found in resistant K562/DOX and SKVLB cells. In contrast, no change in ROS level was observed in MCF-7/DOX cells in parallel with decrease in Mn-SOD and catalase mRNAs and corresponding activities concurrently with high increase in GPx-1 mRNA and activity. As a result of the development of resistance, a similarity was found between the change in ROS level and the change in ho-1 and bcl-2 gene expression, whereas elevation of bcl-xl gene expression was observed in all three types of resistant cells. Particular features of development of adaptive antioxidant response as well as redox-dependent change in bcl-2 gene expression under formation of DOX resistance of cancer cells of different genesis are discussed.

Antioxidants↗
PubMed1991

Subunit separation in reversed micelle system reveals the existence of active centers both on light and heavy gamma-glutamyltransferase subunits.

Regulation of supra-macromolecular composition and catalytic activity of a heterodimeric enzyme, gamma-glutamyltransferase, in the system of Aerosol OT (sodium bis(2-ethylhexyl) sulfosuccinate) reversed micelles in octane were studied. Variation of the surfactant hydration degree (parameter, determining dimensions of the polar inner cavity of the micelle) causes a reversible dissociation of the enzyme to light and heavy subunits. Both enzyme subunits possess catalytic activity. The light and heavy subunits of the enzyme were separated on a preparative scale in a reversed micelle system using ultracentrifugation. The active centers of gamma-glutamyltransferase were studied using its irreversible inhibitor--AT-125 (L-(alpha S, 5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid). Separation of the gamma-glutamyltransferase subunits results in the 'opening' of a new active center located at the heavy subunit. In the dimer form of the enzyme this center is masked and it is not accessible to both substrate and inhibitor molecules.

Binding Sites↗
PubMed1991

[Comparative study of the regulation of catalytic activity of soluble and membrane forms of enzymes in reverse micellar systems. Gamma-glutamyltransferase and aminopeptidase].

The regulations of functioning of water soluble and membrane forms of enzymes in the systems of reversed micelles of surfactants in organic solvents are compared. By an examples of gamma-glutamyltransferase (in AOT reversed micelles in octane) and amino-peptidase (in Brij 96 reversed micelles in cyclohexane) the principal difference in the catalytic activity regulation of water soluble and membrane forms is demonstrated. The catalytic activity of the membrane form depends largely on the surfactant concentration at the constant hydration degree, whereas the activity of the water soluble form is constant under these conditions. The catalytic activity dependence on the surfactant concentration is regarded as a "test for the enzyme's membrane activity".

Aminopeptidases↗
PubMed1989

A new strategy for the study of oligomeric enzymes: gamma-glutamyltransferase in reversed micelles of surfactants in organic solvents.

A heterodimeric enzyme (gamma-glutamyltransferase) was studied in the reversed micellar medium of Aerosol OT (AOT) in octane. As was shown earlier, the size (radius) of inner cavity of the AOT-reversed micelles is determined by their hydration degree, i.e., [H2O]/[AOT] molar ratio, in the system. Owing to this, the dependence of hydrolytic, transpeptidation and autotranspeptidation activities of the enzyme on the hydration degree was investigated using L- and D-isomers of gamma-glutamyl(3-carboxy-4-nitro)anilide and glycylglycine as substrates. For all of the reaction types, the observed dependences are curves with three optima. The optima are found at the hydration degrees, [H2O]/[AOT] = 11, 17 and 26 when the inner cavity radii of reversed micelles are equal to the size of light (Mr 21,000) and heavy (Mr 54,000) subunits of gamma-glutamyltransferase, and to their dimer (Mr 75,000), respectively. Ultracentrifugation experiments showed that a change of the hydration degree resulted in a reversible dissociation of the enzyme to light and heavy subunits. The separation of light and heavy subunits of gamma-glutamyltransferase formed in reversed micelles was carried out and their catalytic properties were studied. The two subunits catalyze hydrolysis and transpeptidation reactions; autotranspeptidation reaction is detected only in the case of the heavy subunit. These findings imply that the reversed micelles of surfactants in organic solvents function as the matrices with adjustable size permitting to regulate the supramolecular structure and the catalytic activity of oligomeric enzymes.

Catalysis↗
PubMed1989

[Regulation of the supramolecular structure and the catalytic activity of gamma-glutamyltransferase in the reversed micelle system].

Regulation mechanisms of the supramolecular structure and the catalytic activity of a heterodimeric enzyme, gamma-glutamyltransferase, in the system of Aerosol OT (AOT) reversed micelles in octane have been studied. gamma-(3-carboxy-4-nitro)-glutamic acid anilide (L- and D-isomers) and glycylglycine were used as substrates to explore the enzyme-catalyzed hydrolase, autotransferase, and transferase reactions. For all types of reactions, the catalytic activity of gamma-glutamyltransferase as a function of the hydration degree has a shape of curves with three optima. The optima of the catalytic activity were detected at hydration degrees [( H2O]/[AOT] = 11, 17, and 26) when radii of the micelle's inner cavity are commensurate with the light and heavy subunits (Mr 21,000 and 54,000, respectively) of gamma-glutamyltransferase as well as with the dimer (Mr 75,000). As ultracentrifugation the change in hydration degree caused a reversible dissociation of the enzyme to the light and heavy subunits. Both subunits catalyze the hydrolase and transferase reactions, whereas the autotransferase activity was detected only for the heavy subunit. Dependencies of catalytic activities of the subunits on the hydration degree have one optimum each (at [H2O]/[AOT] = 11 and 17 for the light and heavy subunits, respectively). When mixing micellar solutions containing both subunits, a third optimum was detected corresponding to the dimer [( H2O]/[AOT] = 26).

Catalysis↗
PubMed1986

[Phosphorylation and inhibition of gamma-glutamyl transferase activity by cAMP-dependent protein kinase].

It was shown that preparations of bovine kidney gamma-glutamyl transferase with different degree of purity are phosphorylated by cAMP-dependent protein kinase. Phosphorylation is accompanied by a simultaneous decrease of both transferase and hydrolase activities of the enzyme. Hence, gamma-glutamyltransferase may serve as a substrate and target of regulation by cAMP-dependent protein kinase.

Animals↗
PubMed1986

[Latent form of glutathione reductase in the rat liver].

The existence of membrane-bound forms of glutathione reductase in rat liver and transplantable hepatoma G-27 was demonstrated, using differential centrifugation techniques. The activity of the sedimentable form of the liver enzyme was detected only in the presence of detergents. Conditions for the manifestation of the latent glutathione reductase activity in whole liver homogenates and in the 105000 g pellet were determined. Solubilization of the latent form of the enzyme in the presence of sodium deoxycholate increases 2-fold the glutathione reductase activity in liver homogenates (but not in hepatoma). Simultaneous determination of the disulfidereductase, nonspecific NADPH-oxidase and gamma-glutamyltransferase (membrane-bound enzyme of glutathione metabolism) activities was performed.

Animals↗
PubMed1984

[Effect of hydrocortisone on gamma-glutamyl transferase activity of the rat liver and hepatoma].

The activity of membrane-bound enzyme gamma-glutamyl transferase (GGT) is twice increased in the liver of normal and tumour-bearing rats after hydrocortisone intramuscular injections (10 mg/kg body weight). At the same time GGT activity is not increased in serum and hepatoma G-27. The glutathione-reductase activity and contents of G-SH and G-S-S-G in the rat liver and hepatoma are not altered by Hydrocortisone action at the different means of hormone administration. Effect of hydrocortisone is studied also on the GGT activity in the liver of newborn rats. The stimulation of GGT activity by hydrocortisone is probably due to an induction of protein synthesis.

Animals↗
PubMed1980

[Partial purification and certain properties of gamma-glutamyltransferase from rat liver and hepatoma].

gamma-Glutamyltransferase (GGT) from the liver and transplantable hepatoma of rats was purified 130- and 170-fold, respectively. The properties of the enzymatic preparations obtained were studied. The optimum pH for the transferase reaction between L-gamma-glutamyl-p-nitroanilide (5 mM) and glycyl-glycine (50 mM) was 8.0--8.2, while that for the auto-transferase reaction (without glycyl-glycine) amounted to 9.3--9.5. The isoelectric points of GGT from the liver correlated with the pH 3.9, 4.2 and 4.4 whereas those of hepatoma enzyme with the pH 5.7, 6.0 and 7.0 GGT obtained from both sources were equally specific for various acceptors at the pH 8.1 and 7.0. It has been shown that metotrexate (0.9 mM) and folic acid (3.5 mM) inhibited both enzymes by 50%.

Animals↗
PubMedDate not supplied

[NP-detecting DNA technologies: solving problems of applied biochemistry].

Heterozygosity of CANP3, ACTN3, and GHR genes in specialized collections was studied using state-of-the-art DNA technologies for DNA analysis. A new dinucleotide deletion (AC) at the beginning of exon 21 was identified in five individuals with heterozygous CANP3 gene. Analysis of polymorphism (SNP1747 C-->T) of ACTN3 gene demonstrated a positive association of allele C with a high muscular performance. Real-time PCR assay of SNP1630 (A-->C) in GHR gene suggested a putative negative association of allele C of this SNP with a high muscular performance.

Actinin↗