Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.3.2.3 (glutathione synthetase)
 678 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Arabidopsis thaliana, trichome cells are specialized unicellular structures with uncertain functions. Based on earlier observations that one of the genes involved in cysteine biosynthesis (Atcys-3A) is highly expressed in trichomes, we have extended our studies in trichome cells to determine their capacity for glutathione (GSH) biosynthesis. First, we have analyzed by in situ hybridization the tissue-specific expression of the genes Atcys-3A and sat5, which encode O-acetylserine(thio)lyase (OASTL) and serine acetyltransferase (SAT), respectively, as well as gsh1 and gsh2, which encode gamma-glutamylcysteine synthetase and glutathione synthetase, respectively. The four genes are highly expressed in leaf trichomes of Arabidopsis, and their mRNA accumulate to high levels. Second, we have directly measured cytoplasmic GSH concentration in intact cells by laser-scanning microscopy after labeling with monochlorobimane as a GSH-specific probe. From these measurements, cytosolic GSH concentrations of 238+/-25, 80+/-2, and 144+/-19 microM were estimated for trichome, basement, and epidermal cells, respectively. Taking into account the volume of the cells measured using stereological techniques, the trichomes have a total GSH content more than 300-fold higher than the basement and epidermal cells. Third, after NaCl treatment, GSH biosynthesis is markedly decreased in trichomes. Atcys-3A, sat5, gsh1, and gsh2 mRNA levels show a decrease in transcript abundance, and [GSH](cyt) is reduced to 47+/-5 microM. These results suggest the important physiological significance of trichome cells related to GSH biosynthesis and their possible role as a sink during detoxification processes.
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PMID:Glutathione biosynthesis in Arabidopsis trichome cells. 1099 73

Glutathione (gamma-glu-cys-gly; GSH) is usually present at high concentrations in most living cells, being the major reservoir of non-protein reduced sulfur. Because of its unique redox and nucleophilic properties, GSH serves in bio-reductive reactions as an important line of defense against reactive oxygen species, xenobiotics and heavy metals. GSH is synthesized from its constituent amino acids by two ATP-dependent reactions catalyzed by gamma-glutamylcysteine synthetase and glutathione synthetase. In yeast, these enzymes are found in the cytosol, whereas in plants they are located in the cytosol and chloroplast. In protists, their location is not well established. In turn, the sulfur assimilation pathway, which leads to cysteine biosynthesis, involves high and low affinity sulfate transporters, and the enzymes ATP sulfurylase, APS kinase, PAPS reductase or APS reductase, sulfite reductase, serine acetyl transferase, O-acetylserine/O-acetylhomoserine sulfhydrylase and, in some organisms, also cystathionine beta-synthase and cystathionine gamma-lyase. The biochemical and genetic regulation of these pathways is affected by oxidative stress, sulfur deficiency and heavy metal exposure. Cells cope with heavy metal stress using different mechanisms, such as complexation and compartmentation. One of these mechanisms in some yeast, plants and protists is the enhanced synthesis of the heavy metal-chelating molecules GSH and phytochelatins, which are formed from GSH by phytochelatin synthase (PCS) in a heavy metal-dependent reaction; Cd(2+) is the most potent activator of PCS. In this work, we review the biochemical and genetic mechanisms involved in the regulation of sulfate assimilation-reduction and GSH metabolism when yeast, plants and protists are challenged by Cd(2+).
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PMID:Sulfur assimilation and glutathione metabolism under cadmium stress in yeast, protists and plants. 1610 96

Cd(2+) causes disturbance of metabolic pathways through severe damage on several levels. Here we present a comprehensive study of Cd(2+)-mediated effects on transcript, enzyme and metabolite levels in a plant without phytochelatin (PC). The moss Physcomitrella patens (Hedw.) B.S.G. was stressed with up to 10 microm Cd(2+) to investigate the regulation of gene transcription and activities of enzymes involved in the assimilatory sulphate reduction pathway and in glutathione biosynthesis. Real-time PCR, specific enzyme assays as well as thiol peptide profiling techniques were applied. Upon supplementation of 10 microm Cd(2+), the moss showed a more than fourfold increase in expression of genes encoding ATP sulphurylase (ATPS), adenosylphosphosulphate reductase, phosphoradenosylphosphorsulphate reductase, sulphite reductase (SiR) and gamma-glutamyl cysteine synthetase (gamma-ECS). Likewise, elevated enzyme activities of gamma-ECS and glutathione synthetase were observed. Contrarily, activity of O-acetylserine (thiol) lyase (OAS-TL), responsible for biosynthesis of cysteine, was diminished. At the metabolite level, nearly doubling of intracellular cysteine and glutathione content was noted, while the moss did not produce any detectable amounts of PCs. These results suggest a Cd(2+)-induced activation of the assimilatory sulphate reduction pathway as well as of glutathione biosynthesis on different levels of regulation.
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PMID:Sulphate assimilation under Cd2+ stress in Physcomitrella patens--combined transcript, enzyme and metabolite profiling. 1691 69