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Emile Levy - One of the best experts on this subject based on the ideXlab platform.

Miguel N. Moreno-carretero - One of the best experts on this subject based on the ideXlab platform.

  • Structural and theoretical studies on rhodium and iridium complexes with 5-nitrosopyrimidines. Effects on the proteolytic Regulatory Enzymes of the renin–angiotensin system in human tumoral brain cells
    Journal of inorganic biochemistry, 2014
    Co-Authors: Nuria A. Illán-cabeza, Antonio R. García-garcía, José Manuel Martínez-martos, María Jesús Ramírez-expósito, Sonia B. Jiménez-pulido, Tomás Peña-ruiz, Miguel N. Moreno-carretero
    Abstract:

    Abstract The reactions of [RhCl(CO)(PPh3)2], [RhCl(CO)2]2 and [IrCl(CO)(PPh3)2] with different 5-nitrosopyrimidines afforded sixteen complexes which have been structurally characterized by elemental analysis, IR and NMR (1H and 13C) spectral methods and luminescence spectroscopy. The crystal and molecular structures of [RhIIICl(VIOH− 1)2(PPh3)], [RhIIICl(DVIOH− 1)2(PPh3)] and [RhII(DVIOH− 1)2(PPh3)2] have been established from single crystal x-ray structure analyses. The three complexes are six-coordinated with both violurato ligands into an equatorial N5,O4-bidentate fashion, but with different mutually arrangements. Theoretical studies were driven on the molecular structure of [RhIIICl(VIOH− 1)2(PPh3)] to assess the nature of the metal–ligand interaction as well as the foundations of the cis–trans (3L–2L) isomerism. An assortment of density functional (SOGGA11-X, B1LYP, B3LYP, B3LYP-D3 and wB97XD) has been used, all of them leading to a similar description of the target system. Thus, a topological analysis of the electronic density within AIM scheme and the study of the Mulliken charges yield a metal–ligand link of ionic character. Likewise, it has been proved that the cis–trans isomerism is mainly founded on that metal–ligand interaction with the relativistic effects playing a significant role. Although most of the compounds showed low direct toxicity against the human cell lines NB69 (neuroblastoma) and U373-MG (astroglioma), they differently modify in several ways the renin–angiotensin system (RAS)-regulating proteolytic Regulatory Enzymes aminopeptidase A (APA), aminopeptidase N (APN) and insulin-regulated aminopeptidase (IRAP). Therefore, these complexes could exert antitumor activity against both brain tumor types, acting through the paracrine regulating system mediated by tissue RAS rather than exerting a direct cytotoxic effect on tumor cells.

  • Antiproliferative effects of palladium(II) complexes of 5-nitrosopyrimidines and interactions with the proteolytic Regulatory Enzymes of the renin–angiotensin system in tumoral brain cells
    Journal of inorganic biochemistry, 2013
    Co-Authors: Nuria A. Illán-cabeza, Antonio R. García-garcía, José Manuel Martínez-martos, María Jesús Ramírez-expósito, Miguel N. Moreno-carretero
    Abstract:

    Seventeen new palladium(II) complexes of general formulaes PdCl2L, PdCl(LH-1)(solvent) and PdCl2(PPh3)2L containing pyrimidine ligands derived from 6-amino-5-nitrosouracil and violuric acid have been prepared and characterized by elemental analysis, IR and NMR ((1)H and (13)C) methods and, two of them, PdCl(DANUH-1)(CH3CN)]·½H2O and [PdCl(2MeOANUH-1)(CH3CN)] by X-ray single-crystal diffraction (DANU: 6-amino-1,3-dimethyl-5-nitrosouracil; 2MeOANU: 6-amino-2-methoxy-5-nitroso-3H-pyrimidin-4-one). The coordination environment around palladium is nearly square planar in the two compounds with different supramolecular arrangements. Crystallographic and spectral data are consistent with a bidentate coordination mode through N5 and O4 atoms when the ligands act in neutral form and N5 and N6 atoms in the monodeprotonated ones. The cytotoxicity of the complexes against human neuroblastoma (NB69) and human glioma (U373-MG) cell lines has been tested showing a considerable antiproliferative activity. Also, the study of the effects of palladium(II) complexes on the renin-angiotensin system (RAS) regulating proteolytic Regulatory Enzymes aminopeptidase A (APA), aminopeptidase N (APN) and insulin-regulated aminopeptidase (IRAP) shows a strong dependence on the compound tested and the tumoral cell type, also affecting different catalytic routes; the compounds affect in a different way the activities of Enzymes of the RAS system, changing their functional roles as initiators of cell proliferation in tumors as autocrine/paracrine mediators.

Sylvain Brunet - One of the best experts on this subject based on the ideXlab platform.

  • Modulation of endoplasmic reticulum-bound cholesterol Regulatory Enzymes by iron/ascorbate-mediated lipid peroxidation
    Free radical biology & medicine, 2000
    Co-Authors: Sylvain Brunet, L. Thibault, Guy Lepage, Ernest G. Seidman, Nadia Dubé, Emile Levy
    Abstract:

    Abstract Mammalian sterol Regulatory Enzymes are integral membrane proteins of the endoplasmic reticulum. They play a critical role in liver cholesterol homeostasis and the maintenance of overall cholesterol balance in different species. Because lipid peroxidation has been implicated in hepatic dysfunction and atherosclerosis, we hypothesized that its occurrence could alter the composition and properties of the bilayer lipid environment, and thereby affect the functions of these membrane proteins. Preincubation of rat liver microsomes with iron (Fe)/ascorbate (50 μM/200 μM), known to induce peroxidation, resulted in a significant inhibition of (i) the rate-limiting enzyme in cholesterol biosynthesis, HMG-CoA reductase (46%, p

  • modulation of endoplasmic reticulum bound cholesterol Regulatory Enzymes by iron ascorbate mediated lipid peroxidation
    Free Radical Biology and Medicine, 2000
    Co-Authors: Sylvain Brunet, L. Thibault, Guy Lepage, Ernest G. Seidman, Nadia Dubé, Emile Levy
    Abstract:

    Abstract Mammalian sterol Regulatory Enzymes are integral membrane proteins of the endoplasmic reticulum. They play a critical role in liver cholesterol homeostasis and the maintenance of overall cholesterol balance in different species. Because lipid peroxidation has been implicated in hepatic dysfunction and atherosclerosis, we hypothesized that its occurrence could alter the composition and properties of the bilayer lipid environment, and thereby affect the functions of these membrane proteins. Preincubation of rat liver microsomes with iron (Fe)/ascorbate (50 μM/200 μM), known to induce peroxidation, resulted in a significant inhibition of (i) the rate-limiting enzyme in cholesterol biosynthesis, HMG-CoA reductase (46%, p

D A Baker - One of the best experts on this subject based on the ideXlab platform.

  • the effect of water stress on the activities of key Regulatory Enzymes of the sucrose to starch pathway in wheat
    Plant Growth Regulation, 2001
    Co-Authors: A Ahmadi, D A Baker
    Abstract:

    Developmental changes in the starch and sucrose content of grains andthe activities of Enzymes of starch synthesis in wheat were studied under waterstress conditions. Water stress caused a marked reduction in the sucrose andstarch content of the grains. Sucrose synthase (SS) and UDP-glucosepyrophosphorylase (UDP-Gppase), showed higher catalytic activity and moreresistance to water stress compared with amyloplastic Enzymes. ADP-glucosepyrophosphorylase (ADP-Gppase) activity was reduced to a low level under bothin situ and osmotic stress conditions in which grainsfailed to accumulate dry matter in vivo. Granule-boundstarch synthase (GBSS) also responded rapidly to in situwater stress treatments as did ADP-Gppase. Reduction in GBSS activity at thetime of growth cessation in situ was less than that ofADP-Gppase and the enzyme did not respond to severe osmotic stress. Solublestarch synthase (SSS) was the enzyme most sensitive to water stress in that itresponded earlier, and to a greater extent, than the other Enzymes. However,under severe dehydration conditions, leading to cessation of growth, thedeclinein SSS activity was less than that for ADP-Gppase. SSS showed the lowestin vitro activity followed by GBSS. These results suggestthat SSS is the site of response to water stress by which the rate of graingrowth can be affected, whereas growth cessation is due mainly to theinactivation of ADP-Gppase.

Luciano F. Huergo - One of the best experts on this subject based on the ideXlab platform.

  • interactions between pii proteins and the nitrogenase Regulatory Enzymes drat and drag in azospirillum brasilense
    FEBS Letters, 2006
    Co-Authors: Luciano F. Huergo, Emanuel M. Souza, Maria B. R. Steffens, Fábio O. Pedrosa, Leda S. Chubatsu, Mike Merrick
    Abstract:

    In Azospirillum brasilense ADP-ribosylation of dinitrogenase reductase (NifH) occurs in response to addition of ammonium to the extracellular medium and is mediated by dinitrogenase reductase ADP-ribosyltransferase (DraT) and reversed by dinitrogenase reductase glycohydrolase (DraG). The PII proteins GlnB and GlnZ have been implicated in regulation of DraT and DraG by an as yet unknown mechanism. Using pull-down experiments with His-tagged versions of DraT and DraG we have now shown that DraT binds to GlnB, but only to the deuridylylated form, and that DraG binds to both the uridylylated and deuridylylated forms of GlnZ. The demonstration of these specific protein complexes, together with our recent report of the ability of deuridylylated GlnZ to be sequestered to the cell membrane by the ammonia channel protein AmtB, offers new insights into the control of NifH ADP-ribosylation.

  • Effects of over-expression of the Regulatory Enzymes DraT and DraG on the ammonium-dependent post-translational regulation of nitrogenase reductase in Azospirillum brasilense
    Archives of microbiology, 2005
    Co-Authors: Luciano F. Huergo, Emanuel M. Souza, Maria B. R. Steffens, M. Geoffrey Yates, Fábio O. Pedrosa, Leda S. Chubatsu
    Abstract:

    Nitrogen fixation in Azospirillum brasilense is regulated at transcriptional and post-translational levels. Post-translational control occurs through the reversible ADP-ribosylation of dinitrogenase reductase (Fe Protein), mediated by the dinitrogenase reductase ADP-ribosyltransferase (DraT) and dinitrogenase reductase glycohydrolase (DraG). Although the DraT and DraG activities are regulated in vivo, the molecules responsible for such regulation remain unknown. We have constructed broad-host-range plasmids capable of over-expressing, upon IPTG induction, the Regulatory Enzymes DraT and DraG as six-histidine-N-terminal fused proteins (His). Both DraT-His and DraG-His are functional in vivo. We have analyzed the effects of DraT-His and DraG-His over-expression on the post-translational modification of Fe Protein. The DraT-His over-expression led to Fe Protein modification in the absence of ammonium addition, while cells over-expressing DraG-His showed only partial ADP-ribosylation of Fe Protein by adding ammonium. These results suggest that both DraT-His and DraG-His lose their regulation upon over-expression, possible by titrating out negative regulators.