Role of ABC transporter MRPA,  -glutamylcysteine synthetase and ornithine decarboxylase in natural antimony-resistant isolates of Leishmania donovani

Oxidant stress mediated by tert-butyl hydroperoxide (t-BOOH) inhibits agonist-stimulated Ca2+ entry and internal store Ca2+ release in cultured endothelial cells. The role of intracellular glutathione in modulating the effects of oxidant stress on Ca2+ signaling was determined in cells preincubated with buthionine-[S,R]-sulfoximine (BSO), an inhibitor of gamma-glutamylcysteine synthetase, or 1-chloro-2,4-dinitrobenzene (CDNB), a cosubstrate for glutathione-S-transferase. BSO and CDNB decreased endothelial cell glutathione content by 85 and 97%, respectively (control glutathione, 21.5 +/- 2.3 nmol/mg protein). Each agent accelerated the time-dependent effects of t-BOOH on Ca2+ signaling in fura 2-loaded cells and potentiated the inhibition of bradykinin-stimulated 45Ca2+ efflux induced by t-BOOH. These results indicate that decreased availability of reduced glutathione, the primary cosubstrate for glutathione peroxidase, potentiates the effect of hydroperoxide oxidant stress on receptor-operated Ca2+ entry across the plasmalemma and Ca2+ release from internal stores. The present findings suggest that intracellular glutathione availability and/or glutathione redox cycle activity are critically important modulators of oxidant inhibition of Ca(2+)-dependent signal transduction.

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The Maltodextrin System of Escherichia coli: Metabolism and Transport

Journal of Bacteriology ◽

10.1128/jb.187.24.8322-8331.2005 ◽

2005 ◽

Vol 187 (24) ◽

pp. 8322-8331 ◽

Cited By ~ 51

Author(s):

Renate Dippel ◽

Winfried Boos

Keyword(s):

Escherichia Coli ◽

Abc Transporter ◽

Binding Protein ◽

Glycogen Synthesis ◽

Equilibrium Conditions ◽

Per Se ◽

Maltodextrin Phosphorylase ◽

Internal Level

ABSTRACT The maltose/maltodextrin regulon of Escherichia coli consists of 10 genes which encode a binding protein-dependent ABC transporter and four enzymes acting on maltodextrins. All mal genes are controlled by MalT, a transcriptional activator that is exclusively activated by maltotriose. By the action of amylomaltase, we prepared uniformly labeled [14C]maltodextrins from maltose up to maltoheptaose with identical specific radioactivities with respect to their glucosyl residues, which made it possible to quantitatively follow the rate of transport for each maltodextrin. Isogenic malQ mutants lacking maltodextrin phosphorylase (MalP) or maltodextrin glucosidase (MalZ) or both were constructed. The resulting in vivo pattern of maltodextrin metabolism was determined by analyzing accumulated [14C]maltodextrins. MalP− MalZ+ strains degraded all dextrins to maltose, whereas MalP+ MalZ− strains degraded them to maltotriose. The labeled dextrins were used to measure the rate of transport in the absence of cytoplasmic metabolism. Irrespective of the length of the dextrin, the rates of transport at a submicromolar concentration were similar for the maltodextrins when the rate was calculated per glucosyl residue, suggesting a novel mode for substrate translocation. Strains lacking MalQ and maltose transacetylase were tested for their ability to accumulate maltose. At 1.8 nM external maltose, the ratio of internal to external maltose concentration under equilibrium conditions reached 106 to 1 but declined at higher external maltose concentrations. The maximal internal level of maltose at increasing external maltose concentrations was around 100 mM. A strain lacking malQ, malP, and malZ as well as glycogen synthesis and in which maltodextrins are not chemically altered could be induced by external maltose as well as by all other maltodextrins, demonstrating the role of transport per se for induction.

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Down-modulation of c-myc expression by phorbol ester protects CEM T leukaemia cells from starvation-induced apoptosis: role of ornithine decarboxylase and polyamines

Cell Death and Differentiation ◽

10.1038/sj.cdd.4400909 ◽

2001 ◽

Vol 8 (10) ◽

pp. 967-976 ◽

Cited By ~ 10

Author(s):

L Tiberio ◽

J A M Maier ◽

L Schiaffonati

Keyword(s):

Ornithine Decarboxylase ◽

Phorbol Ester ◽

Induced Apoptosis

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Role of ornithine decarboxylase on glycolytic enzyme induction during thymocyte proliferation.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)48163-x ◽

1987 ◽

Vol 262 (31) ◽

pp. 15232-15235

Author(s):

K Brand

Keyword(s):

Ornithine Decarboxylase ◽

Enzyme Induction ◽

Glycolytic Enzyme ◽

Thymocyte Proliferation

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Effects of nonsulfur and sulfur amino acids on the regulation of hepatic enzymes of cysteine metabolism

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1999.277.1.e144 ◽

1999 ◽

Vol 277 (1) ◽

pp. E144-E153 ◽

Cited By ~ 11

Author(s):

Deborah L. Bella ◽

Christine Hahn ◽

Martha H. Stipanuk

Keyword(s):

Amino Acids ◽

Specific Activity ◽

Mrna Level ◽

Basal Diet ◽

Cysteine Dioxygenase ◽

Sulfur Amino Acids ◽

Subunit Mrna ◽

Cysteine Metabolism ◽

Glutamylcysteine Synthetase

To determine the role of nonsulfur vs. sulfur amino acids in regulation of cysteine metabolism, rats were fed a basal diet or diets supplemented with a mixture of nonsulfur amino acids (AA), sulfur amino acids (SAA), or both for 3 wk. Hepatic cysteine-sulfinate decarboxylase (CSDC), cysteine dioxygenase (CDO), and γ-glutamylcysteine synthetase (GCS) activity, concentration, and mRNA abundance were measured. Supplementation with AA alone had no effect on any of these measures. Supplementation of the basal diet with SAA, with or without AA, resulted in a higher CDO concentration (32–45 times basal), a lower CSDC mRNA level (49–64% of basal), and a lower GCS-heavy subunit mRNA level (70–76%). The presence of excess SAA and AA together resulted in an additional type of regulation: a lower specific activity of all three enzymes was observed in rats fed diets with an excess of AA and SAA. Both SAA and AA played a role in regulation of these three enzymes of cysteine metabolism, but SAA had the dominant effects, and effects of AA were not observed in the absence of SAA.

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