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Biomedical subjects

S S Mardanian

Publications and source records attributed to S S Mardanian.

At least 19 recordsLinked to original sources
PubMed2002

[Activity of pleural fluid adenosine deaminase in tuberculous pleurisy].

Examining the activity of adenosine deaminase in the pleural fluids of 69 patients with tuberculous pleurisy of various etiology from the clinics of Armenia indicated that it was greater than the threshold value of 20 U/L in 95.7 of 47 patients with tuberculous pleurisy. The specificity of this parameter for this disease was 0.91. The prognostic value of the test with positive and negative results was 0.96 and 0.94, respectively. The diagnostic value of the ADA test was 0.94.

Adenosine Deaminase↗
PubMed1996

[The role of tryptophan in appearance of adenosine deaminase activity].

Chemical modification of tryptophan residues with N-bromosuccinimide and their photooxidation in the presence of trichloroethanol inhibited the activity of adenosine deaminase purified from gray and white matter of calf brain. Only two of six modified residues are important for enzyme activity. Preliminary kinetic data indicate that these essential tryptophan residues are adjacent to the substrate-binding site of the enzyme.

Adenosine Deaminase↗
PubMed1996

[Modification of the histidine in rat skeletal muscle deaminase by diethylpyrocarbonate].

Diethylpyrocarbonate inactivated rat skeletal muscle AMP deaminase in 10 mM phosphate buffer, pH 6.5, at 23 degrees with the second order rate constant of 580 M-1.min-1. Absorbtion at 240 nm was concomitantly increase. Enzyme activity can be restored by hydroxylamine. The pH-dependence of inactivation indicates the involvement of a group with pKa 6.9. The data suggest that modification of one histidyl residue per subunit inactivates the activity of tetrameric AMP deaminase.

AMP Deaminase↗
PubMed1995

[Interaction of 2Fe-2S-ferredoxins from plants and adrenal cortex with detergents].

The interactions of 2Fe-2S ferredoxins from bovine adrenal cortex, blue-green algae and leaves of three plant species with some positively and negatively charged as well as with uncharged detergents, have been studied. These interactions generally resulted in the destruction of active centers of ferredoxins represented by the 2Fe-2S cluster. The role of oxidants (oxygen and potassium ferricyanide) in cluster destruction by detergents has been established. The opposite sensitivity of plant and animal ferredoxins to anionic and nonionic detergents was revealed.

Adrenal Cortex↗
PubMed1994

[Isolation, purification, and comparative study of the properties of adenosine deaminase from five regions of the cattle brain].

Adenosine deaminase from the white and gray matter of the large hemispheres, cerebellum, medulla oblongata and pituitary anterior lobe has been isolated and purified. The pH optimum, Km, molecular mass, yield and specific activities for all the enzyme preparations have been determined. Gel filtration and electrophoresis data point to the heterogeneity of the enzyme. The lack of effects of SH-reagents suggests the absence of an essential SH-group. Among five bivalent metal ions, only Cu2+ irreversibly inhibited the enzyme activity in all the preparations.

Adenosine Deaminase↗
PubMed1990

The role of tryptophanyl residues in electron transfer from NADPH--adrenodoxin reductase to adrenodoxin.

Chemical modification of tryptophanyl residues of NADPH - adrenodoxin reductase by N - bromosuccinimide and trichloroethanol prevents the interaction of the enzyme with adrenodoxin. The modification does not touch other amino acid residues besides tryptophan (tyrosine, lysine and cysteine) or disturb the structure of protein. The presence of adrenodoxin suppresses the modification. The data obtained indicate the participation of adrenodoxin reductase tryptophan residues in the interaction with adrenodoxin.

Adrenal Cortex↗
PubMed1988

Dimeric structure of rat skeletal muscle AMP-deaminase subunit.

AMP-deaminase from rat skeletal muscle was purified by affinity chromatography on phosphocellulose and gel-filtration on Sephadex G-200. It was established that disulfide bridges and hydrogen bonds were not essential for stability of enzyme oligomeric structure. The dimeric structure of enzyme subunit with Mr 76 kDa (S1) was detected by means of PAGE in the presence of SDS: besides the S1 there were also exhibited two additional bands with Mr 42 (S2) and 33 (S3) kDa. Repeated SDS-PAGE of S1 has revealed the same three protein bands. These results indicate the possibility of dissociation of S1-subunit into two subunits with close Mr values.

AMP Deaminase↗
PubMed1987

[The role of tryptophan residues of NADPH-adrenodoxin reductase in the formation of complex with adrenodoxin].

Chemical modification of tryptophan residues by N-bromosuccinimide was used to determine the role of these residues in the NADPH-adrenodoxin-catalyzed reduction of adrenodoxin, dichlorophenolindophenol and ferricyanide. It was shown that the rate of reduction of all electron acceptors diminishes with modification of tryptophan residues. The most significant decrease of the enzyme activity is observed in case of adrenodoxin-catalyzed reactions. It was suggested that tryptophan residues are responsible for the adrenodoxin reductase interaction with adrenodoxin.

Adrenal Cortex↗
PubMed1987

[Study of the conformation of neurospecific cardioactive glycoproteins by optical spectroscopy].

Using selective fluorescence quenching and circular dichroism techniques, the conformation of protein carriers of earlier detected cardiotropic hypothalamic neurohormones was investigated. The experimental results point to essential differences in the structural organization of the above compounds that were designated according to the type of their binding to corresponding hormones as BNH, BNC and BNS. For instance, the circular dichroism spectrum of BNS is typical of proteins that are characterized by a high content of non-ordered structures, a low content of beta-structures and an almost complete absence of alpha-helices. BNC and BNH with nearly the same content of alpha-helical structures are distinguished by the number of "non-ordered glomes" which are more abundant in BNC. These results are in good agreement with the fluorescence quenching data.

Animals↗
PubMed1984

[Luminescent properties of NADPH: adrenodoxin reductase].

The fluorescent and phosphorescent properties of NADPH-adrenodoxin reductase were investigated. It was shown that the fluorescence of protein tryptophanyls was quenched completely by acrylamide and partially by ionic quenchers (I- and Cs+). A removal of the prosthetic group from the protein causes insignificant changes in fluorescent properties of the enzyme. The denaturation of the enzyme by urea was accompanied by growth of quenching parameters. Indeed, some differences were observed in the quenching of flavin fluorescence by ionic quenchers (I- and Cs+). NADPH appeared to be an efficient quencher of NADPH-adrenodoxin reductase tryptophan fluorescence. Using Förster's equations for non-radiative energy transfer, the distance between NADPH-binding site and tryptophanyls was evaluated to 35-40 A.

Acrylamide↗
PubMed1982

[Cytochromes c and P-450 as terminal acceptors in a reconstituted system of mitochondrial hydroxylation].

Both cytochromes c and P-450 can be reduced in vitro by a mitochondrial hydroxylation chain consisting of flavoprotein, adrenodoxin and NADPH as electron donors. The effects of pH, ionic strength, content and stoichiometry of intermediate electron carriers on the reduction rate of cytochromes c and P-450 have been compared. The data obtained demonstrate that the reduction of these cytochromes proceeds by different ways. It has been found that cytochrome c has an inhibitory effect on cytochrome P-450 reduction. On the other hand, cytochrome P-450 remarkably activates the process of cytochrome c reduction.

Adrenal Cortex↗
PubMed1979

[Effects of the medium on the rate of electron transfer in a reconstituted system of mitochondrial hydroxylation].

Effects of ionic strength, pH, viscosity, concentrations of components and nature of acceptor on the rate of NADPH oxidation and acceptor reduction were studied in a hydroxylation system containing adrenodoxin reductase, adrenodoxin and cytochrome P450 or cytochrome c. The maximal rate was observed with 0.05--0.10 M phosphate buffer, pH 6.0--6.5 and at the adrenoxin/flavoprotein/cytochrome ratio of 1 : 1 : 1. The electron transfer rate was decreased with an increase in viscosity. Cytochrome P450 is more efficient as a terminal acceptor as compared to cytochrome c or indigodisulphonate.

Adrenodoxin↗
PubMed1979

[Electron carriers of adrenocortical mitochondria. Terminal systems].

A procedure for isolation of cytochrome oxidase and cytochrome P-450 from adrenocortical mitochondria was developed. The heme and copper contents, subunit composition, optical and EPR spectra for these enzymes were determined. The effects of pH, substrates and some inhibitors on the spectra of cytochrome P-450 were studied. It was found that cytochrome oxidase did not inhibit the reactions catalyzed by cytochrome P-450; cytochrome P-450 had no inhibiting effect on the oytochrome oxidase activity.

Adrenal Cortex↗
PubMed1977

[Fluorescent properties of b-type ferredoxins].

Fluroescent spectra of six b-type ferredoxins of plant and animal origins were obtained. All investigated proteins do not contain tryptophan. The emission maxima of the native proteins, apoproteins prepared by various methods, and denaturated proteins are compared. The effects of pH, ionic strength and ferricyanide on the ferredoxins fluorescence were studied. "Unusual" emission at 340nm noted previously for adrenal ferredoxin was observed for spinach and Chenopodium album ferredoxins too. The localization of tyrosine fluorescent maximum at 340nm in the ferredoxins is not due to interaction of tyrosine with the iron-sulfur center. The data obtained allow to suggest that the tyrosine residues in ferredoxins have different environments.

Adrenal Glands↗
PubMed1976

[Adrenal cortex cytochrome c].

The method of preparation of highly purified cytochrome c from bovine adrenal cortex is described. Absolute spectra of the protein in reduced and oxidized states and some its physico-chemical properties are investigated.

Adrenal Cortex↗