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

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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)

The amount of reduced glutathione in transplantable hepatomas and in a primary DEN-induced hepatoma is lower than in normal liver. In all tumors examined, the glutathione decrease is not due to an increase of oxidized glutathione. In this paper the in vitro activities of two enzymes involved in glutathione synthesis, gamma-glutamylcysteine synthetase and glutathione synthetase, are studied in normal adult rat liver, in regenerating rat liver and in highly anaplastic Yoshida AH-130 hepatoma cells. The activity of these enzymes was determined in the postmicrosomal supernatant fraction as nmoles of [U-14C]-glutamate incorporated into product per mg of soluble protein. In Yoshida AH-130 hepatoma, the gamma-glutamylcysteine synthetase and glutathione synthetase activities are lower in respect to normal liver. This is in agreement with the low glutathione content observed in the hepatoma cells. On the other hand, in regenerating liver, there are minimal differences in comparison with normal liver.
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PMID:Glutathione synthesis in normal liver and in Yoshida AH-130 hepatoma. 380 95

Enzyme studies on placenta, cultured skin fibroblasts, and erythrocytes from two sisters with the inborn error 5-oxoprolinuria (pyroglutamic aciduria) indicate that the metabolic lesion in this disease is at the glutathione synthetase (EC 6.3.2.3) step of the gamma-glutamyl cycle. Excessive urinary excretion of 5-oxoproline by these patients appears to be associated with increased synthesis of gamma-glutamyl-cysteine and formation of 5-oxoproline from this dipeptide. Thus, 5-oxoproline is produced in amounts that exceed the normal capacity of 5-oxoprolinase to convert it to glutamate. The data indicate that it may be possible to identify individuals who are heterozygous for this trait by determinations of erythrocyte glutathione synthetase.
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PMID:Glutathione synthetase deficiency, an inborn error of metabolism involving the gamma-glutamyl cycle in patients with 5-oxoprolinuria (pyroglutamic aciduria). 415 48

The enzymatic production of glutathione (GSH) has been studied in a bioreactor system using toluene-treated cells of Escherichia coli B transformed with recombinant plasmids for gamma-glutamylcysteine synthetase (GSH-I) and glutathione synthetase (GSH-II). As reported previously the genes for both enzymes were separately cloned onto vector plasmid pBR322. The plasmid for GSH-I was designated pGS100-2 and that for GSH-II as pGS200. The effect on GSH production in the bioreactor system, containing an ATP regenerating system, of using cells containing various hybrid plasmids has now been explored. Three kinds of hybrid plasmids, designated pGS300, pGS400, and pGS500, were constructed by subcloning the genes in pGS100-2 and pGS200 onto vector plasmid pBR325. pGS300 contained the E. coli B chromosomal DNA fragment with a gene for GSH-I in the PstI site of pBR325. pGS400 also contained E. coli B chromosomal DNA fragment with a gene for GSH-II in the HindIII site of pBR325. In contrast, pGS500 contained two kinds of DNA fragments with the genes for GSH-I and GSH-II in the PstI and HindIII sites of pBR325, respectively. All the hybrid plasmids thus prepared were stably maintained in E. coli cells when chloramphenicol was included at 10 micrograms/ml in the medium. The activity of the cells containing pGS300 was higher than that of the cells containing pGS400, although the former activity did not come up to that of cells having both pGS300 and pGS400. The highest glutathione-producing activity was found in the case of the cells transformed with pGS500 carrying both genes for GSH-I and GSH-II on the vector plasmid pBR325. About 5 mg/ml of glutathione was produced by E. coli cells with pGS500 from 80 mM L-glutamate, 20 mM L-cysteine, and 20 mM glycine within 3 h at 37 degrees C.
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PMID:Construction of glutathione-producing strains of Escherichia coli B by recombinant DNA techniques. 614 39

To gain insight into cellular metabolism underlying the glutathione (GSH) alterations induced by surgical trauma, we assessed postoperative skeletal muscle GSH metabolism and its redox status in 10 patients undergoing elective abdominal surgery. Muscle biopsy specimens were taken from the quadriceps femoris muscle before and at 24 and 72 h after surgery. GSH concentrations decreased by 40% at 24 h postoperatively compared with the paired preoperative values (P < 0.001) and remained low at 72 h (P < 0.01). The concentration of GSH disulfide (GSSG) did not significantly change throughout the study period, whereas the total GSH (as GSH equivalent) concentration decreased after surgery. Of the GSH constituent amino acids, the concentration of cysteine remained unchanged throughout the study period (from 28.2 +/- 10.1 preoperatively to 29.4 +/- 13.9 at 24 h postoperatively and to 28.3 +/- 15.6 micromol/kg wet wt at 72 h postoperatively). Despite a reduction in glutamate concentration by 40% 24 h after surgery, no correlation was established between GSH and glutamate concentrations postoperatively. Activity of gamma-glutamylcysteine synthetase did not change significantly after surgery, whereas GSH synthetase activity decreased postoperatively (from 66.4 +/- 19.1 preoperatively to 41.0 +/- 10.5 24 h postoperatively, P < 0.01, and to 46.0 +/- 11.7 microU/mg protein 72 h postoperatively, P < 0.05). The decrease of GSH was correlated to the reduced GSH synthetase activity seen at 24 h postoperatively. These results indicate that the skeletal muscle GSH pool is diminished in patients after surgical trauma. The depletion of the GSH pool is associated with a decreased activity of GSH synthetase, indicating a decreased GSH synthetic capacity in skeletal muscle tissue.
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PMID:Surgical trauma decreases glutathione synthetic capacity in human skeletal muscle tissue. 968 40

This paper reports that the glutathione (GSH)-deficient mutant, cad2-1, of Arabidopsis is deficient in the first enzyme in the pathway of GSH biosynthesis, gamma-glutamylcysteine synthetase (GCS). The mutant accumulates a substrate of GCS, cysteine, and is deficient in the product, gamma-glutamylcysteine. In vitro enzyme assays showed that the cad2-1 mutant has 40% of wild-type levels of GCS activity but is unchanged in the activity of the second enzyme in the pathway, GSH synthetase. The CAD2 locus maps to chromosome 4 and is tightly linked to a gene, GSHA, identified by a previously isolated cDNA. A genomic clone of GSHA complements both the phenotypic and biochemical deficiencies of the cad2-1 mutant. The nucleotide sequence of the gene has been determined and, in the mutant, this gene contains a 6 bp deletion within an exon. These data demonstrate that the CAD2 gene encodes GCS. The cad2-1 mutation is close to the conserved cysteine which is believed to bind the substrate glutamate and the specific inhibitor L-buthionine-[S,R] sulfoximine (BSO). Both root growth and GCS activity of the cad2-1 mutant was less sensitive than the wild-type to inhibition by BSO, indicating that the mutation may alter the affinity of the inhibitor binding site.
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PMID:The glutathione-deficient, cadmium-sensitive mutant, cad2-1, of Arabidopsis thaliana is deficient in gamma-glutamylcysteine synthetase. 980 29

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.
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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

GSH is the major low-molecular-mass thiol in most organisms. The tripeptide maintains a reduced intracellular environment and protects cellular components from damaging oxidation. GSH is synthesized by the action of two ATP-dependent enzymic steps, in which gamma-glutamylcysteine synthetase (gamma-GCS) catalyses the ligation of glutamate and cysteine and subsequently glutathione synthetase (GS) adds glycine to the dipeptide. Recently it was shown that the synthesis of gamma-glutamylcysteine is crucial for the survival of the erythrocytic stages of the malaria parasite Plasmodium falciparum by using the specific gamma-GCS inhibitor buthionine sulphoximine. In order to investigate further the synthetic pathway of the tripeptide in the parasite, GS was cloned and expressed recombinantly. The deduced amino acid sequence of P. falciparum GS shares only a moderate degree of identity with other known GSs, but the residues responsible for substrate and co-factor binding are almost all conserved, with the exception of the ones involved in gamma-glutamylcysteine binding. The protein is active as a dimer, with a subunit molecular mass of 77 kDa, and the addition of reducing reagents such as dithiothreitol is essential in maintaining enzymic activity, indicating that thiol groups are important for stability and enzymic activity. The K(app)(m) values for gamma-glutamyl-alpha-aminobutyrate, ATP and glycine were determined to be 107.1 microM, 59.1 microM and 5.04 mM, respectively, and the V(max) of 5.24 +/- 0.7 micromol.min(-1).mg(-1) was in the same range as that of the mammalian enzymes. However, the negative co-operativity observed for gamma-glutamylcysteine binding to the rat enzyme was not found for the parasite protein. This may be due to the alteration of several amino acids in the gamma-glutamylcysteine-binding site.
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PMID:Glutathione synthetase from Plasmodium falciparum. 1196 86

Mice that lack the Nrf2 basic-region leucine-zipper transcription factor are more sensitive than wild-type (WT) animals to the cytotoxic and genotoxic effects of foreign chemicals and oxidants. To determine the basis for the decrease in tolerance of the Nrf2 homozygous null mice to xenobiotics, enzyme assay, Western blotting and gene-specific real-time PCR (TaqMan) have been used to examine the extent to which hepatic expression of GSH-dependent enzymes is influenced by the transcription factor. The amounts of protein and mRNA for class Alpha, Mu and Pi glutathione S-transferases were compared between WT and Nrf2 knockout (KO) mice of both sexes under both constitutive and inducible conditions. Among the class Alpha and class Mu transferases, constitutive expression of Gsta1, Gsta2, Gstm1, Gstm2, Gstm3, Gstm4 and Gstm6 subunits was reduced in the livers of Nrf2 mutant mice to between 3% and 60% of that observed in WT mice. Induction of these subunits by butylated hydroxyanisole (BHA) was more marked in WT female mice than in WT male mice. TaqMan analyses showed the increase in transferase mRNA caused by BHA was attenuated in Nrf2(-/-) mice, with the effect being most apparent in the case of Gsta1, Gstm1 and Gstm3. Amongst class Pi transferase subunits, the constitutive hepatic level of mRNA for Gstp1 and Gstp2 was not substantially affected in the KO mice, but their induction by BHA was dependent on Nrf2; this was more obvious in female mutant mice than in male mice. Nrf2 KO mice exhibited reduced constitutive expression of the glutamate cysteine ligase catalytic subunit, and, to a lesser extent, the expression of glutamate cysteine ligase modifier subunit. Little variation was observed in the levels of glutathione synthase in the different mouse lines. Thus the increased sensitivity of Nrf2(-/-) mice to xenobiotics can be partly attributed to a loss in constitutive expression of multiple GSH-dependent enzymes, which causes a reduction in intrinsic detoxification capacity in the KO animal. These data also indicate that attenuated induction of GSH-dependent enzymes in Nrf2(-/-) mice probably accounts for their failure to adapt to chronic exposure to chemical and oxidative stress.
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PMID:Loss of the Nrf2 transcription factor causes a marked reduction in constitutive and inducible expression of the glutathione S-transferase Gsta1, Gsta2, Gstm1, Gstm2, Gstm3 and Gstm4 genes in the livers of male and female mice. 1199 5

An assay of gamma-glutamylcysteine synthetase (gamma-GCS) and glutathione synthetase (GS) in crude extracts of cultured cells and tissues is described. It represents a novel combination of known methods, and is based on the formation of glutathione (GSH) from cysteine, glutamate and glycine in the presence of rat kidney GS for the assay of gamma-GCS, or from gamma-glutamylcysteine and glycine for the assay of GS. GSH is then quantified by the Tietze recycling method. Assay mixtures contain the gamma-glutamyl transpeptidase (GGT) inhibitor acivicin in order to prevent the degradation of gamma-glutamylcysteine and of the accumulating GSH, and dithiothreitol in order to prevent the oxidation of cysteine and gamma-glutamylcysteine. gamma-GCS and GS levels determined by this method are comparable to those determined by others. The method is suitable for the rapid determination of gamma-GCS GS in GGT-containing tissues and for the studies of induction of gamma-GCS and GS in tissue cultures.
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PMID:A spectrophotometric assay of gamma-glutamylcysteine synthetase and glutathione synthetase in crude extracts from tissues and cultured mammalian cells. 1204 60

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.
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PMID:4-hydroxynonenal induces glutamate cysteine ligase through JNK in HBE1 cells. 1236 7


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