Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:6.3.2.3 (glutathione synthetase)
678 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

GSH synthesis occurs via two enzymatic steps catalyzed by glutamate-cysteine ligase (GCL, made up of two subunits) and GSH synthetase (GS). Recently, we described coordinate induction of GCL subunits and GS. To study GS transcriptional regulation, we have cloned and characterized a 2.2-kb 5'-flanking region of the rat GS (GenBank accession number AF333982). One transcriptional start site is located at 51 nucleotides upstream of the translational start site. The rat GS promoter drove efficiently luciferase expression in H4IIE cells. Sequential deletion analysis revealed DNA regions that are involved in positive and negative regulation. One repressor identified was NF1. tert-Butylhydroquinone (TBH) exerted a dose- and time-dependent increase in the mRNA level and promoter activity of both GCL subunits and GS. TBH increased protein binding to several regions of the GS promoter, c-jun expression, and activator protein 1 (AP-1) binding activity to several of the putative AP-1-binding sites of the GS promoter. Blocking AP-1 binding with dominant-negative c-jun led to decreased basal expression and significantly blocked the TBH-induced increase in promoter activity and mRNA level of all three genes. In conclusion, AP-1 is required for basal expression of GCL and GS; while NF1 serves as a repressor of GS, increased AP-1 transactivation is the predominant mechanism for coordinate induction of GCL and GS expression by TBH.
...
PMID:Role of AP-1 in the coordinate induction of rat glutamate-cysteine ligase and glutathione synthetase by tert-butylhydroquinone. 1209 5

The mechanism underlying age-related neurodegenerative diseases is still an area of significant controversy. Increased evidence suggests that oxidative stress contributes importantly to neuronal damage observed in the brains of aged animals and in neurodegenerative diseases. Glutathione (GSH), the most abundant intracellular nonprotein thiol, plays an important role in antioxidant defense. The concentration of this important antioxidant decreases with age in the brain, which is accompanied by an increase in oxidative damage to macromolecules. The mechanism underlying the age-associated decline in GSH content in the brain, however, is not clear. In this study, we demonstrate for the first time that the expression of the regulatory subunit of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in de novo GSH synthesis, decreases with age in cerebellum, cerebral cortex, and hippocampus of Fisher 344 rats. This was accompanied by a decline in GCS activity and GSH content. There were no significant differences in either the concentrations of cysteine and glutathione disulfide (GSSG) or the activities of glutathione synthetase (GS), gamma-glutamyl traspeptidase (GGT), and glutathione reductase (GR) in the brains from different age groups. Our results suggest that the age-associated decrease in GSH in the brain may result from the down-regulation of GCS regulatory subunit and consequently a decrease in the activity of GCS.
...
PMID:Down-regulation of gamma-glutamylcysteine synthetase regulatory subunit gene expression in rat brain tissue during aging. 1211 65

In the roots of pea plants (Pisum sativum L.) cultivated with 20 [mu]M CdCl2 for 3 d, synthesis of phytochelatins [PCs or ([gamma]EC)nG, where [gamma]EC is [gamma]glutamylcysteine and G is glycine] and homophytochelatins [h-PCs, ([gamma]EC)n[beta]-alanine] is accompanied by a drastic decrease in glutathione (GSH) content, but an increase in homoglutathione (h-GSH) content. In contrast, the in vitro activity of GSH synthetase increases 5-fold, whereas h-GSH synthetase activity increases regardless of Cd exposure. The consititutive enzyme PC synthase, which catalyzes the transfer of the [gamma]-EC moiety of GSH to an acceptor GSH molecule thus producing ([gamma]EC)2G, is activated by heavy metals, with Cd and Cu being strong activators and Zn being a very poor activator. Using h-GSH or hm-GSH for substrate, the synthesis rate of([gamma]EC)2[beta]-alanine and [gamma]EC)2-serine is only 2.4 and 0.3%, respectively, of the sythesis rate of ([gamma]EC)2G with GSH as substrate. However, in the presence of a constant GSH level, increasing the concentration of h-GSH or hm-GSH results in increased synthesis of ([gamma]EC)2[beta]-alanine or ([gamma]EC)2-serine, respecively; simultaneously, the synthesis of ([gamma]EC)2G is inhibited. [gamma]EC is not a substrate of PC synthase. These results are best explained by assuming that PC synthase has a [gamma]EC donor binding site, which is very specific for GSH, and a [gamma]EC acceptor binding site, which is less specific and accepts several tripeptides, namely GSH, h-GSH, and hm-GSH.
...
PMID:Synthesis of Phytochelatins and Homo-Phytochelatins in Pisum sativum L. 1222 79

Two cell lines of tomato (Lycopersicon esculentum Mill cv VFNT-Cherry) were systematically compared for their capacity to tolerate cadmium. Unselected CdS cells died in the presence of 0.3 mM CdCl2. CdR6-0 cells, which were selected from CdS, survived and grew in medium supplemented with 0.3 mM CdCl2. Growth of CdR6-0 cells under this condition was accompanied by synthesis of cadmium-binding phytochelatins and maintenance of cellular glutathione (GSH) levels. CdR6-0 cells also exhibited increased tolerance to buthionine sulfoximine, in both the presence and absence of 0.1 mM CdCl2. The specific activity of [gamma]-glutamylcysteine synthetase (EC 6.3.2.2) was approximately 2-fold higher in CdR6-0 cells than in CdS cells, whereas there was no difference between cell lines in specific activity of GSH synthetase (EC 6.3.2.3). Increased activity of the first enzyme of GSH biosynthesis in CdR6-0 cells, presumably a result of selection for increased cadmium tolerance, provides an enhanced capacity to synthesize GSH and to maintain the production of phytochelatins in response to cadmium. This adaptation may contribute to the enhanced cadmium tolerance of CdR6-0 cells.
...
PMID:Increased Activity of [gamma]-Glutamylcysteine Synthetase in Tomato Cells Selected for Cadmium Tolerance. 1223 24

Glutathione is the most abundant non-protein thiol in the cell, with roles in cell cycle regulation, detoxification of xenobiotics, and maintaining the redox tone of the cell. The glutathione content is controlled at several levels, the most important being the rate of de novo synthesis, which is mediated by two enzymes, glutamate cysteine ligase (GCL), and glutathione synthetase (GS), with GCL being rate-limiting generally. The GCL holoenzyme consists of a catalytic (GCLC) and a modulatory (GCLM) subunit, which are encoded by separate genes. In the present study, the signaling mechanisms leading to de novo synthesis of GSH in response to physiologically relevant concentrations of 4-hydroxy-2-nonenal (4HNE), an endproduct of lipid peroxidation, were investigated. We demonstrated that exposure to 4HNE resulted in increased content of both Gcl mRNAs, both GCL subunits, phosphorylated JNK1 and c-Jun proteins, as well as Gcl TRE sequence-specific AP-1 binding activity. These increases were attenuated by pretreating the cells with a novel membrane-permeable JNK pathway inhibitor, while chemical inhibitors of the p38 or ERK pathways were ineffective. These data reveal that de novo GSH biosynthesis in response to 4HNE signals through the JNK pathway and suggests a major role for AP-1 driven expression of both Gcl genes in HBE1 cells.
...
PMID:4-hydroxynonenal induces glutamate cysteine ligase through JNK in HBE1 cells. 1236 7

Hepatic synthesis and plasma levels of glutathione are markedly decreased in chronic liver disease. Because glutathione turnover is highest in kidneys, we examined whether changes in kidney glutathione occur in chronic cholestasis and whether they are related to kidney dysfunction in liver disease. Kidney and plasma GSH and GSSG were measured 1) in bile duct-ligated (BDL) rats; 2) in healthy rats after bile acid loading to mimic cholestasis; and 3) after irreversible inhibition of glutathione synthetase with buthionine-sulfoximine (BSO), where glutathione consumption, urinary volume, and sodium excretion were also estimated. In addition, gamma-glutamylcysteine synthetase (gamma-GCS) mRNA, protein, and enzymatic specific activity were measured in kidney tissue after BDL. After BDL, kidney GSH and GSSG increased within hours by 67 and 66%, respectively. The increases were not related to plasma glutathione, which decreased below control values. Intravenous bile acid loading caused identical increases in GSH and GSSG as occurred after BDL, when glycine- or taurine-conjugated dihydroxy bile acids were administered. Glutathione consumption, as estimated after blocking of de novo synthesis with BSO, was significantly increased after BDL (127 vs. 44 nmol x g-1 x min-1). gamma-GCS mRNA and enzymatic specific activity were significantly reduced 5 days after BDL, whereas protein concentrations did not change. The urinary sodium concentration was 70% lower in BDL than in control rats. Depletion of renal glutathione normalized sodium excretion by increasing urinary sodium concentration and urinary volume. The increase in kidney glutathione after BDL seems to be mediated by an increase in plasma bile acids and is critically related to sodium retention. The increase in GSH consumption despite reduced gamma-GCS activity indicates a decreased GSH turnover tentatively due to reduced renal GSH efflux by competition with organic anions at membrane transport proteins.
...
PMID:Increase in renal glutathione in cholestatic liver disease is due to a direct effect of bile acids. 1238 94

A recombinant strain E. coli II-1, which exhibited high glutathione (GSH) biosynthetic activity and high stability, was constructed by transforming plasmid pGH501 which contains gene gsh I and gsh II into a wild type strain E. coli II. 4 g/L GSH accumulated extracellularly by using toluene-treated cell. In GSH biosynthetic system, GSH production was improved by increasing the concentration of L-glutamate, while inhibited by L-cysteine if it's concentration was beyond 20 mmol/L. In GSH biosynthetic reaction, the apparent little consumption of L-glutamate and glycine was concluded experimentally to be that toluene-treated E. coli II-1 cells still contained high concentration of L-glutamate and glycine. According to the change of energy cofactor in the GSH biosynthetic process, a possible GSH biosynthetic mechanism controlled by E. coli II-1, was proposed: the energy donator of reaction catalyzed by glutathione synthetase (GSH-II) was ADP but not ATP, the reaction was rate-limited step within the whole GSH biosynthetic process, high concentration of ADP might inhibit the activity of GSH-II. Further degradation of GSH was prevented by the addition of 100 mmol/L L-serine and potassium borate mixture. In such case, 23.0 mmol/L (about 7.1 g/L) GSH accumulated at 3 h.
...
PMID:[Construction of recombinant E. coli with high glutathione biosynthetic activity and the biosynthetic process]. 1254 83

It is well known that intracellular antioxidant glutathione (GSH) plays major roles in the maintenance of redox status and defense of oxidative stress. Ras, a small GTP-binding protein, may send growth-stimulating message to the nucleus through downstream Rac oncoprotein and superoxide (O(2*-)). These findings led us to investigate the effects of GSH and melatonin, a free-radical scavenger, on Ras-Rac-O(2*-)-related growth signal transduction. Our results demonstrate that overexpression of the inducible Ha-ras oncogene by isopropyl-beta-D-thiogalactoside (IPTG) increases the levels of reactive oxygen species (ROS, including O(2*-) and hydrogen peroxide (H(2)O(2))) and GSH in an Ha-ras-transformed NIH/3T3 fibroblast cell line. On the contrary, melatonin significantly suppresses ras-triggered cell growth by inhibiting the increase of ROS and GSH. Moreover, severe apoptosis of this transformed cell line occurred when the cell redox balance between ROS and GSH was dramatically changed in the presence of IPTG and L-buthionine-[S,R]-sulfoximine (BSO, a specific inhibitor of GSH synthetase). That BSO-induced cell apoptosis needs Ras to increase the ROS level was demonstrated by the free-radical scavenger melatonin. It effectively blocked cell apoptosis, but cell growth was also slowed without affecting Ras expression. Based on our studies, two approaches can be applied to treating ras-related cancers. One is utilizing melatonin to suppress cancer cell proliferation, and the other is utilizing BSO to induce cancer-cell apoptosis. Cotreatment of ras-related cancer cells with melatonin and BSO stops cell growth as well as apoptosis. Whether these cancer cells will undergo further regression or become recurrent merits investigation.
...
PMID:Glutathione depletion-induced apoptosis of Ha-ras-transformed NIH3T3 cells can be prevented by melatonin. 1261 60

Although Cd(2+) is a more effective inducer of phytochelatin (PC) synthesis than Zn(2+) in higher plants, we have observed greater induction of PC synthesis by Zn(2+) than Cd(2+) in the marine green alga, Dunaliella tertiolecta. To elucidate this unique regulation of PC synthesis by Zn(2+), we investigated the effects of Zn(2+) and Cd(2+) on the activities of both phytochelatin synthase (PC synthase) and enzymes in the GSH biosynthetic pathway. PC synthase was more strongly activated by Cd(2+) than by Zn(2+), but the difference was not very big. On the other hand, gamma-glutamylcysteine synthetase (gamma-ECS) and glutathione synthetase (GS) were activated by both heavy metals, but their activities were higher in Zn-treated cells than in Cd-treated cells. Dose-dependent stimulation of intracellular reactive oxygen species (ROS) production was observed with Zn(2+), but not Cd(2+) treatment. These results suggest that Zn(2+) strongly promotes the synthesis of GSH through indirect activation of gamma-ECS and GS by stimulating ROS generation. This acceleration of the flux rate for GSH synthesis might mainly contribute to high level PC synthesis.
...
PMID:Regulation of phytochelatin synthesis by zinc and cadmium in marine green alga, Dunaliella tertiolecta. 1262 Mar 58

Glutathione (GSH) plays a major role in the cellular defence against oxidative stress and other vital cellular functions. It therefore seems inevitable that patients with severe depletion of GSH will not survive. However, at least some with glutathione synthetase (GS) deficiency do. This study was done to determine whether these patients have a mechanism to compensate for their GSH deficiency. Cell-free extracts of cultured fibroblasts from 9 patients with GS deficiency and 9 control subjects were analysed by HPLC for low-molecular-weight thiol compounds. The patients' cells contained 7.4 nmol of GSH per mg of protein (median; range 2.8-25.2) compared to 33.0 nmol in control fibroblasts (range 26.7-51.4) (p < 0.01). On the other hand, the patients' cells accumulated 18.1 nmol of gamma-glutamylcysteine (gamma-GC) per mg of protein (median; range 6.9-71.7), whereas the control cells contained 0.1 nmol (range 0.05-0.16) (p < 0.01). The cysteine concentrations in the patients' cells were 20.7 nmol/mg protein (median; range 9.4-52.9) compared to 8.9 nmol in control cells (range 3.0-12.4) (p < 0.01). Cultured fibroblasts from patients with GS deficiency have low levels of GSH, but instead accumulate gamma-GC. We suggest that gamma-GC, which contains both reactive groups of GSH (i.e. the sulphydryl and gamma-glutamyl groups), can compensate for GSH in the cellular defence against oxidative stress. Thus, gamma-GC may alleviate, but only partly prevent, serious consequences of insufficient GSH levels in affected patients. Since the sum of the levels of GSH and gamma-GC in GS-deficient cells (median 31.5 nmol/mg protein, range 16.2-79.0) was similar to the level of GSH alone in control cells (33.0 nmol/mg protein, range 26.7-51.4), we propose that the cultured fibroblasts may have a mechanism to regulate in a coordinated way the levels of GSH and gamma-GC; for instance, by both compounds acting as feedback inhibitors of gamma-GC synthetase.
...
PMID:Glutathione synthetase deficiency: is gamma-glutamylcysteine accumulation a way to cope with oxidative stress in cells with insufficient levels of glutathione? 1263 41


<< Previous 1 2 3 4 5 6 7 8 9 10

---