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Biomedical subjects

N A Zorin

Publications and source records attributed to N A Zorin.

At least 19 recordsLinked to original sources
PubMed1998

Rhodobacter capsulatus HypF is involved in regulation of hydrogenase synthesis through the HupUV proteins.

The photosynthetic bacterium Rhodobacter capsulatus contains a membrane-bound [NiFe]hydrogenase encoded by the hupSL genes. We show in this study that hypF mutants are devoid of hydrogenase activity and lack the HupL protein. We also observed that, in contrast to the wild-type strain B10, transcription of the hupSL genes was not stimulated by H2 in the hypF mutants RS13 and BSE19. Complementation of the hypF mutants with the plasmid borne hypF gene restored hydrogenase activity to wild-type levels and inducibility by H2. The R. capsulatus hupU and hupV gene products share significant similarities with the small (HupS) and the large (HupL) hydrogenase subunits, respectively. Active HupUV proteins can catalyze the hydrogen-deuterium exchange reaction. In whole cells, this H-D exchange is distinguishable from the H-D exchange catalyzed by the membrane-bound HupSL proteins by its insensitivity to O2 and to acetylene. By measuring the formation of H2 and HD in exchange with D2 uptake, we demonstrated that the hypF mutants have no active HupUV nor HupSL proteins. H-D exchange activity, of both HupUV and HupSL, was restored by hypF gene complementation. These data indicate that the HypF protein participates not only in the maturation of HupSL, but also in the maturation of the HupUV proteins and that the latter are involved in the cellular response to H2.

Bacterial Proteins↗
PubMed1998

Effect of human alpha2-macroglobulin on proliferative activity of rat tumor cells.

The Walker carcinosarcoma cells were cultured in the medium with low concentration (0.25%) of fetal calf serum, in the presence of native or methylamine-treated (modified) human alpha 2-macroglobulin (alpha 2-MG) in vitro. The proliferative activity (3H-thymidine incorporation) of these cells increased in the presence of one or the other alpha 2-MG preparation. It allows to suppose that the human alpha 2-MG may serve as a growth-stimulating factor of tumour cells.

Animals↗
PubMed1997

HupUV proteins of Rhodobacter capsulatus can bind H2: evidence from the H-D exchange reaction.

The H-D exchange reaction has been measured with the D2-H2O system, for Rhodobacter capsulatus JP91, which lacks the hupSL-encoded hydrogenase, and R. capsulatus BSE16, which lacks the HupUV proteins. The hupUV gene products, expressed from plasmid pAC206, are shown to catalyze an H-D exchange reaction distinguishable from the H-D exchange due to the membrane-bound, hupSL-encoded hydrogenase. In the presence of O2, the uptake hydrogenase of BSE16 cells catalyzed a rapid uptake and oxidation of H2, D2, and HD present in the system, and its activity (H-D exchange, H2 evolution in presence of reduced methyl viologen [MV+]) depended on the external pH, while the H-D exchange due to HupUV remained insensitive to external pH and O2. These data suggest that the HupSL dimer is periplasmically oriented, while the HupUV proteins are in the cytoplasmic compartment.

Bacterial Proteins↗
PubMed1996

Inhibition by iodoacetamide and acetylene of the H-D-exchange reaction catalyzed by Thiocapsa roseopersicina hydrogenase.

The kinetics of H-D isotope exchange catalyzed by the thermostable hydrogenase from Thiocapsa roseopersicina have been studied by analysis of the exchange between D2 and H2O. The pH dependence of the exchange reaction was examined between pH 2.5 and pH 11. Over the whole pH range, HD was produced at a higher initial velocity than H2, with a marked optimum at pH 5.5; a second peak in the pH profile was observed at around pH 8.5. The rapid formation of H2 with respect to HD in the D2/H2O system is consistent with a heterolytic cleavage of D2 into D+ and an enzyme hydride that can both exchange with the solvent. The H-D-exchange activity was lower in the H2/D2O system than in the D2/H2O system. The other reactions catalyzed by the hydrogenase, H2 oxidation and H2 evolution, are pH dependent; the optimal pH were 9.5 for H2 uptake and 4.0 for H2 production. Treatment of the active form of hydrogenase by iodoacetamide led to a slow and irreversible inhibition of the H-D exchange. When iodo[1-14C]acetamide was incubated with hydrogenase, the radioactive labeling of the large subunit was higher for the enzyme activated under H2 than for the inactive oxidized form. Cysteine residues were identified as the alkylated derivative by amino acid analysis. Acetylene, which inhibits H-D exchange and abolishes the Ni-C EPR signal, protected the enzyme from irreversible inhibition by iodoacetamide. These data indicate that iodoacetamide can reach the active site of the H2-activated hydrogenase from T. roseopersicina. This was not found to be the case with the seleno hydrogenase from Desulfovibrio baculatus (now Desulfomicrobium baculatus). Cysteine modification by iodoacetamide upon activation of the enzyme concomitant with loss of H-D exchange indicates that reductive activation makes at least one Cys residue of the active site available for alkylation.

Acetylene↗
PubMed1996

Reversible hydrogenase of Anabaena variabilis ATCC 29413: catalytic properties and characterization of redox centres.

The catalytic and spectroscopic properties of the reversible hydrogenase from the cyanobacterium Anabaena variabilis have been examined. The hydrogenase required reductive activation in order to elicit hydrogen-oxidation activity. Carbon monoxide was a weak (Ki=35 microM), reversible and competitive inhibitor. A flavin with the chromatographic properties of FMN, and nickel were detected in the purified enzyme. A. variabilis hydrogenase exhibited electron paramagnetic resonance (EPR) spectra in its hydrogen-reduced state, indicative of [2Fe-2S] and [4Fe-4S] clusters. Although no EPR signals due to nickel were detected, the results are consistent with the enzyme being a flavin-containing hydrogenase of the nickel-iron type.

Anabaena↗
PubMed1996

[Proteinase inhibitors as markers of stomach cancer].

The study was concerned with assay of alpha 1.2-microglobulins (MGs) and pregnancy-associated alpha 1.2-glucoproteins (PAGs) which are considered nonspecific markers. The study group included 52 patients with gastric precancer and 40 patients with gastric tumors. A correlation was established between MG levels and carcinogenesis which may be interpreted as an indicator of malignant transformation of chronic ulcer or metastasis development following radical surgery for stomach cancer.

Biomarkers, Tumor↗
PubMed1995

Interaction of human pregnancy-associated plasma protein-A with serine proteinases.

Human pregnancy-associated plasma protein A (PAPP-A) inhibited significantly the proteolytic activity of bovine trypsin and human plasmin. Trypsin or plasmin treatment of PAPP-A resulted in the generation of a major 85 kDa component and the rapid cleavage of internal thiol esters. The results indicated that both of these serine proteinases bound in a 1:1 stoichiometry to PAPP-A. The PAPP-A-bound enzymes were found to be enzymatically active towards small synthetic substrates and inaccessible to inactivation by soybean trypsin inhibitor and alpha 1-proteinase inhibitor. The mechanism of proteinase inhibition was likely to be entrapment, as described for alpha 2-macroglobulin.

Amino Acid Sequence↗
PubMed1994

Changes in tissue distribution of rat alpha 1-macroglobulin and pregnancy-associated alpha 1-glycoprotein after inflammatory injury.

Antiserum against rat alpha 1-macroglobulin (alpha 1MG) was produced in rabbits. Antiserum against rat pregnancy-associated alpha 1-glycoprotein (PAG) was obtained by immunization with a partly purified PAG preparation and absorption of the serum with male rat serum. Acute inflammation was produced in non-pregnant female rats by a single intramuscular injection of turpentine. The concentrations of both macroglobulins in the serum and in tissue extracts were measured by rocket immunoelectrophoresis at various times up to 7 days after injury. Inflammation produced in the rats resulted in moderately elevated serum levels of these proteins soon after injury. At first, alpha 1MG levels in a number of tissues (heart, lung, kidney, spleen, pancreas, uterus and ovary) were depressed markedly; they then stabilized. The elevated serum concentrations of alpha 1MG remained unchanged during inflammation. The store of PAG in the tissues was rapidly depleted and its serum level decreased to a normal value 7 days after injury. Our findings indicate that alpha 1MG plays a more important role in maintenance of the proteinase inhibitory potential in the rat than does PAG.

Acute-Phase Reaction↗
PubMed1994

[The effect of plasmin-modified proteinase inhibitors on macroglobulin production by human blood mononuclear cells in culture].

A study was made of the influence of plasmin (PL) complexes with alpha 2-macroglobulin (MG) and alpha 2-antiplasmin on secretion of MG, pregnancy-associated alpha 2-glycoprotein (PAG), and pregnancy-associated plasma protein A (PAPP-A) by mononuclear cells (MC), obtained from human peripheral blood. It has been shown that incubation of the MG-PL complexes with MC resulted in the increase in concentrations of all these macroglobulins (MG, PAG, and PAPP-A) in supernatants of cultured MC. We revealed the same effects of AP-PL with regard to the secretion of PZP and PAPP-A. However, this complex was found to suppress MG production by cultured MC. The effects found were dose dependent and some of them differed greatly in men and women, resp.

Cells, Cultured↗
PubMed1994

[Pregnancy-associated alpha2-glycoprotein and trophoblastic beta1-glycoprotein in the diagnosis of pyoinflammatory diseases after Cesarean section].

Blood serum pregnancy-associated alpha 2-glycoprotein and trophoblastic beta 1-glycoprotein were measured in puerperants with the normal postpartum period and with that complicated by pyo-inflammatory diseases after abdominal delivery. The levels of both proteins were found reduced in the patients with pyo-inflammatory diseases developing after cesarean section as early as on day 1 postpartum. that of alpha 2-glycoprotein by 1.2 times, that of trophoblastic beta 1-glycoprotein twofold.

Adolescent↗
PubMed1993

[Hepatocyte receptors for proteinase inhibitor complexes with plasmin].

Hepatocyte receptors have been found for such complexes as alpha 2-macroglobulin-plasmin, pregnancy-associated plasma protein A-plasmin, and pregnancy-associated alpha 2-glycoprotein-plasmin, molecular masses of these receptors being estimated. The proteinaceous component of hepatocyte membranes contains heavy chains of plasmin and a 50 kDa fragment of plasmin molecule. These chains and the fragment are able to bind the native alpha 2-antiplasmin. Using immunoblotting no hepatocyte receptors for native macroglobulins, and alpha 2-antiplasmin-plasmin, alpha 1-proteinase inhibitor were detected.

Cell Fractionation↗
PubMed1991

Three-dimensional structure of the nickel-containing hydrogenase from Thiocapsa roseopersicina.

The three-dimensional structure of the nickel-containing hydrogenase from Thiocapsa roseopersicina has been determined at a resolution of 2 nm in the plane and 4 nm in the vertical direction by electron microscopy and computerized image processing on microcrystals of the enzyme. The enzyme forms a large ring-shaped complex containing six each of the large (62-kDa) and small (26-kDa) subunits. The complex is very open, with six well-separated dumbbell-shaped masses surrounding a large cylindrical hole. Each dumbbell is interpreted as consisting of one large and one small subunit.

Electrophoresis, Polyacrylamide Gel↗
PubMed1991

[Comparative study of immunosuppressive properties of pregnancy- associated protein A, alpha 2-glucoprotein and alpha 2-macroglobulin].

Effects of high-molecular proteinase inhibitors on spontaneous and mitogen-induced lymphocyte proliferation were examined in males and pregnant and non-pregnant females. All three proteins, A protein, alpha 2-glycoprotein, and alpha 2-macroglobulin were found to be potent immunosuppressors and their activity was determined by the stage of pregnancy, the dose and mode of mitogenic lymphocyte stimulation.

Culture Media↗
PubMed1991

[The effect of steroid sex hormones on the biosynthesis of alpha 2-macroglobulin and pregnancy-associated alpha 2-glycoprotein in cultures of peripheral blood mononuclear cells].

The peripheral blood mononuclears are capable of intense biosynthesis of alpha 2-macroglobulin and of weak biosynthesis of pregnancy-associated alpha 2-glycoprotein. Sex hormones of men and non-pregnant women exert no influence on the protein biosynthesis. During pregnancy alpha 2-macroglobulin biosynthesis is shortly activated, although it does not depend on the influence of sex hormones. All the steroid sex hormones provide a short-term biosynthesis of this protein during the II trimester of pregnancy, while testosteron inhibits it during the III trimester. Possible mechanisms of control of biosynthesis of these proteins are discussed.

Cells, Cultured↗