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)

Primary cultures of adult rat hepatocytes shift into the growth phase when plated at low density (LD). We used this model to examine changes in glutathione (GSH) metabolism, since cells undergoing active growth may be more susceptible to environmental toxins. When primary cultures of adult rat hepatocytes were plated on collagen or Matrigel-precoated dishes, cell number and GSH varied inversely. This density effect on cell GSH occurred as early as 2 h after plating, when the media contained 1 mM methionine, but was delayed until 20 h if the media contained only 0.5 mM cystine. The density effect on GSH synthesis occurred in the absence of serum, hormones, changes in cell volume, GSH efflux, ATP levels, and uptake of methionine or cystine and was blocked by cycloheximide or actinomycin D. When methionine was available, the cellular cysteine level was 65% higher at LD than at high density (HD). gamma-Glutamylcysteine synthetase (GCS) activity was 64% higher at LD than at HD. GSH synthetase activity was unaffected by density. Both the increase in cellular cysteine levels and GCS activity were blocked by cycloheximide and actinomycin D. When cells were cocultured using cluster plates and Transwell inserts for 4 h, cell GSH of HD cells was unaffected by the density of cocultured cells; however, LD cells exhibited significantly lower GSH and GCS activity when cocultured with HD cells than when cocultured with LD cells. Cysteine levels were elevated in the LD cells regardless of the density of cocultured cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Am J Physiol 1992 Dec
PMID:Loss of suppression of GSH synthesis at low cell density in primary cultures of rat hepatocytes. 147 63

The activity and the kinetic properties of glutathione synthetase and the concentrations of non-protein bound thiols of the gamma-glutamyl cycle were measured in 11 human fibroblast cell strains. Six of these strains were derived from patients suffering from 5-oxoprolinuria, a recessive genetic disease characterized by a deficiency in glutathione synthetase; the other cell strains were derived from healthy heterozygous or homozygous relatives of the patients. The glutathione synthetase activities of homozygous deficient strains were 1/3 of control values while those of heterozygous strains were 2/3 of control values. The total thiol concentration was lower in only 3 of the 6 deficient homozygotes and that of glutathione (GSH) was lower in only 4 of the 6 deficient homozygotes. This lower GSH level was at least partly offset by an accumulation of gamma-glutamylcysteine, a precursor of GSH, which is almost completely absent from control cells. The total quantities of thiols and GSH in plateau phase cells were about 50% and 30% respectively of the levels in growth phase cells. Approximately 80% of the GSH was in the reduced form in both quiescent and growing cells.
Clin Chim Acta 1987 Dec
PMID:Low molecular weight thiol content in glutathione synthetase-deficient human fibroblasts. 343 51

The effects of long term intake of dietary alcohol on myocardial glutathione metabolism and taurine content were studied in rats. Alcohol, comprising more than 30% of the dietary calorie content, was administered to male CFY rats for six weeks. Compared with the controls, the left ventricle of the alcohol treated animals had an increased taurine content (18.4(2.6) vs 13.1(2.5) mumol X g wet weight-1) and a slightly, but not significantly, decreased reduced glutathione content. To assess the glutathione metabolism in the myocardium, the activities of glutathione reductase, glutathione peroxidase, glutathione-S-transferase, gamma-glutamylcysteine synthetase, and glutathione synthetase were measured. Significant increases were found in the activities of glutathione reductase (0.65(0.03) U.g wet weight-1 in the controls and 0.80(0.05) U.g wet weight-1 in the alcohol treated rats) and glutathione-peroxidase after six weeks of alcohol ingestion. Only slight, non-significant changes were found for the other enzymes investigated. It is thus apparent that in the myocardium of rats treated long term with ethanol the previously observed enhanced lipoperoxidation is not necessarily associated with severe glutathione depletion, and an increase in the activity of glutathione reductase might be responsible, at least in part, for the preservation of glutathione.
Cardiovasc Res 1986 Dec
PMID:Effects of long term alcohol ingestion on glutathione metabolising enzymes and taurine contents in the myocardium of rats. 380 27

The nucleotide sequence of the cloned DNA, 1,478 bp in length coding for glutathione synthetase (GSH-II) of E. coli B has been determined. Amino acid and nucleotide sequence analyses have assigned the open reading frame for GSH-II, starting with the ATG near its 5' terminus. The molecular weight calculated from the predicted amino acid sequence is 35,559 daltons, being in good agreement with that of a GSH-II subunit estimated by the SDS-PAGE method. Several signal sequences conserved in the promoter regions of E. coli were found in the non-coding regions of the gsh-II gene. They include the Shine-Dalgarno sequence, the Pribnow box and the sequence conserved in the "-35 region" with a preferable spacing from each other for an efficient transcription. Downstream from the termination codon, the inverted repeat sequences were present, followed by 6 successive T's. These structural features found in the non-coding regions have suggested to be involved in regulatory functions for the gsh-II gene expression.
Nucleic Acids Res 1984 Dec 21
PMID:Complete nucleotide sequence of the E. coli glutathione synthetase gsh-II. 639 55

Two forms of glutathione synthetase deficiency have been described. While one form is mild, causing hemolytic anemia, the other more severe form causes 5-oxo-prolinuria with secondary neurological involvement. Despite the existence of two deficiency phenotypes, Southern blots hybridized with a glutathione synthetase cDNA suggest that there is a single glutathione synthetase gene in the human genome. Analysis of somatic cell hybrids showed the human glutathione synthetase gene (GSS) to be located on chromosome 20, and this assignment has been refined to subband 20q11.2 using in situ hybridization.
Genomics 1995 Dec 10
PMID:The gene encoding human glutathione synthetase (GSS) maps to the long arm of chromosome 20 at band 11.2. 882 53

The crystal structure of Escherichia coli B glutathione synthetase (GSHase) has been determined at the optimal catalytic condition pH 7.5. The most significant structural difference from the structure at pH 6.0 is the movement of the central domain towards the N-terminal domain almost as a rigid body. As a result of this movement, new interdomain and intersubunit polar interactions are formed which stabilize the dimeric structure further. The structure of GSHase at optimal pH was compared with 294 other known protein structures in terms of the spatial arrangements of secondary structural elements. Three enzymes (D-alanine: D-alanine ligase, succinyl-CoA synthetase and the biotin carboxylase subunit of acetyl-CoA carboxylase) were found to have structures similar to the ATP-binding site of GSHase, which extends across two domains. The ATP-binding sites in these four enzymes are composed of two antiparallel beta-sheets and are different from the classic mononucleotide-binding fold. Except for these proteins, no significant structural similarity was detected between GSHase and the other ATP-binding proteins. A structural motif in the N-terminal domain of GSHase has been found to be similar to the NAD-binding fold. This structural motif is shared by a number of other proteins that bind various negatively charged molecules.
Protein Eng 1996 Dec
PMID:Crystal structure of glutathione synthetase at optimal pH: domain architecture and structural similarity with other proteins. 901 Sep 22

The recently developed PSI-BLAST method for sequence database search and methods for motif analysis were used to define and expand a superfamily of enzymes with an unusual nucleotide-binding fold, referred to as palmate, or ATP-grasp fold. In addition to D-alanine-D-alanine ligase, glutathione synthetase, biotin carboxylase, and carbamoyl phosphate synthetase, enzymes with known three-dimensional structures, the ATP-grasp domain is predicted in the ribosomal protein S6 modification enzyme (RimK), urea amidolyase, tubulin-tyrosine ligase, and three enzymes of purine biosynthesis. All these enzymes possess ATP-dependent carboxylate-amine ligase activity, and their catalytic mechanisms are likely to include acylphosphate intermediates. The ATP-grasp superfamily also includes succinate-CoA ligase (both ADP-forming and GDP-forming variants), malate-CoA ligase, and ATP-citrate lyase, enzymes with a carboxylate-thiol ligase activity, and several uncharacterized proteins. These findings significantly extend the variety of the substrates of ATP-grasp enzymes and the range of biochemical pathways in which they are involved, and demonstrate the complementarity between structural comparison and powerful methods for sequence analysis.
Protein Sci 1997 Dec
PMID:A diverse superfamily of enzymes with ATP-dependent carboxylate-amine/thiol ligase activity. 941 15

Malaria-infected red blood cells are under a substantial oxidative stress. Glutathione metabolism may play an important role in antioxidant defense in these cells, as it does in other eukaryotes. In this work, we have determined the levels of reduced and oxidized glutathione (GSH and GSSG, respectively) and their distributions in the parasite, and in the host-cell compartments of human erythrocytes infected with the malaria parasite Plasmodium falciparum. In intact trophozoite-infected erythrocytes, [GSH] is low and [GSSG] is high, compared with the levels in normal erythrocytes. Normal erythrocytes and the parasite compartment display high GSH/GSSG ratios of 321.6 and 284.5, respectively, indicating adequate antioxidant defense. This ratio drops to 26.7 in the host-cell compartment, indicating a forceful oxidant challenge, the low ratios resulting from an increase in GSSG and a decline in GSH concentrations. On the other hand, the concentrations of GSH and GSSG in the parasite compartment remain physiological and comparable to their concentrations in normal red blood cells. This results from de novo glutathione synthesis and its recycling, assisted by the intensive activity of the hexose monophosphate shunt in the parasite. A large efflux of GSSG from infected cells has been observed, its rate being similar from free parasites and from intact infected cells. This result suggests that de novo synthesis by the parasite is the dominating process in infected cells. GSSG efflux from the intact infected cell is more than 60-fold higher than the rate observed in normal erythrocytes, and is mediated by permeability pathways that the parasite induces in the erythrocyte's membrane. The main route for GSSG efflux through the cytoplasmic membrane of the parasite seems to be due to a specific transport system and occurs against a concentration gradient. Gamma-glutamylcysteine [Glu(-Cys)] and GSH can penetrate through the pathways from the extracellular space into the host cytosol, but not into that of the parasite. This implies that the parasite membrane is impermeable to these peptides, and that the host cannot supply GSH to the parasite as suggested previously. Exogenous Glu(-Cys) is not converted into GSH in the host cell, arguing that GSH synthetase may not be functional. Compartment analysis of Mg2+ in infected erythrocytes revealed that the host compartment exhibits a low concentration of Mg2+ (0.5 mM) in comparison with the parasite compartment (4 mM) and the normal erythrocytes (1.5-3 mM). The drop in [Mg2+] results in cessation of Glu(-Cys) synthesis, and hence of GSH synthesis in the host-cell compartment. The decrease in [Mg2+] can affect other Mg2+-ATP-dependent functions, such as Na+ and Ca2+ active efflux. The present investigation confirms that the host-cell compartment is oxidatively distressed, whereas the parasite is efficiently equipped with anti-oxidant means that protect the parasite from the oxidative injury. The parasite has a huge capacity for de novo synthesis of GSH and for the reduction of GSSG. Part of the GSSG that is actively extruded from the parasite is reduced to GSH in the host cell whose own GSH synthesis is crippled.
Eur J Biochem 1997 Dec 15
PMID:The malaria parasite supplies glutathione to its host cell--investigation of glutathione transport and metabolism in human erythrocytes infected with Plasmodium falciparum. 946 Dec 89

Neoadjuvant cisplatin-based chemotherapy has been widely used in the last decade for organ preservation or unresectable disease in advanced stage head and neck cancer. We examined the expression of a series of tumor markers that have been associated with chemotherapy resistance in pretreatment biopsies from 68 patients who received cisplatin-based neoadjuvant chemotherapy at either of two institutions. Patients received either cisplatin/5-fluorouracil (n = 49) or cisplatin/paclitaxel (n = 19). Expression of p53, glutathione S-transferase pi (GSTpi), thymidylate synthase (TS), c-erbB2, and multidrug resistance-associated protein was examined by immunohistochemistry. Expression of glutathione synthetase mRNA was measured by in situ hybridization. The overall response rate for cisplatin-based neoadjuvant treatment was 79%. The expression of several of the tumor markers was associated with resistance to neoadjuvant treatment, but none reached statistical significance. Overall survival (OS) was strongly correlated with the absence of p53 expression. The OS at 3 years was 81% in the p53-negative group, whereas it was 30% in the p53-positive group for patients treated with neoadjuvant chemotherapy (P < 0.0001). Expression of GST pi and TS was also significantly correlated with decreased OS after neoadjuvant treatment. At 3 years, the OS rate was 82% in the low GSTpi score group, compared to 46% in the high GSTpi score group (P = 0.0018). In the TS-negative group, the 3-year OS rate was 71% compared with 40% in the TS-positive group (P = 0.0071). We conclude that p53, GSTpi, and TS may be clinically important predictors of survival in patients receiving neoadjuvant chemotherapy for head and neck cancer.
Clin Cancer Res 1999 Dec
PMID:Prognostic value of p53, glutathione S-transferase pi, and thymidylate synthase for neoadjuvant cisplatin-based chemotherapy in head and neck cancer. 1063 46

The biosynthesis of reduced glutathione (GSH) is carried out by the enzymes gamma-glutamylcysteine synthetase (GCL) and GSH synthetase. GCL is the rate-limiting step and represents a heterodimeric enzyme comprised of a catalytic subunit (GCLC) and a ("regulatory"), or modifier, subunit (GCLM). The nonhomologous Gclc and Gclm genes are located on mouse chromosomes 9 and 3, respectively. GCLC owns the catalytic activity, whereas GCLM enhances the enzyme activity by lowering the K(m) for glutamate and increasing the K(i) to GSH inhibition. Humans have been identified with one or two defective GCLC alleles and show low GSH levels. As an initial first step toward understanding the role of GSH in cellular redox homeostasis, we have targeted a disruption of the mouse Gclc gene. The Gclc(-/-) homozygous knockout animal dies before gestational day 13, whereas the Gclc(+/-) heterozygote is viable and fertile. The Gclc(+/-) mouse exhibits a gene-dose decrease in the GCLC protein and GCL activity, but only about a 20% diminution in GSH levels and a compensatory increase of approximately 30% in ascorbate-as compared with that in Gclc(+/+) wild-type littermates. These data show a reciprocal action between falling GSH concentrations and rising ascorbate levels. Therefore, the Gclc(+/-) mouse may be a useful genetic model for mild endogenous oxidative stress.
Biochem Biophys Res Commun 2000 Dec 20
PMID:Knockout of the mouse glutamate cysteine ligase catalytic subunit (Gclc) gene: embryonic lethal when homozygous, and proposed model for moderate glutathione deficiency when heterozygous. 1111 86


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