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At least 973 records · Page 54Linked to original sources
PubMed1984

Rainbow trout liver microsomal lipid peroxidation. The effect of purified glutathione peroxidase, glutathione S-transferase and other factors.

Glutathione peroxidase (glutathione: hydrogen-peroxide oxidoreductase, EC 1.11.1.9) was purified approximately 600-fold from rainbow trout liver soluble fraction and its activity in the NADPH microsomal lipid peroxidation system tested. The enzyme has an approximate molecular weight of 100 000, contains four subunits and four atoms of selenium per mol protein. No selenium-independent glutathione peroxidase activity could be attributed to glutathione S-transferase (EC 2.5.1.18) in trout liver. Glutathione peroxidase together with glutathione (GSH) did not provide any additional protection in the in vitro liver microsomal lipid peroxidation system over and above that provided by GSH alone. Microsomal lipid peroxidation was, however, reduced by a partially purified glutathione S-transferase together with GSH. The protection provided by dialysed liver cytosol in this system was not GSH-dependent, showing that other factors in addition to glutathione S-transferase are involved. Of other possible factors, vitamin E reduced lipid peroxidation in this system. Concentrations of vitamin E in microsomes before and after peroxidation in vitro indicated that protective cytosolic factor(s) act prior to the termination of the free radical chain reactions effected by vitamin E. A GSH-dependent protective factor was present in microsomal protein, malondialdehyde formation in the in vitro microsomal system being markedly reduced in the presence of 5 mM GSH but not significantly lowered by 1 mM GSH.

Animals↗
PubMed1983

A set of inhibitors for discrimination between the basic isozymes of glutathione transferase in rat liver.

A set of inhibitors including hematin, bromosulfophthalein, and triethyltin bromide was used for discrimination and identification of the major basic isozymes of glutathione transferase in rat liver cytosol. Six enzymes are formed as binary combinations of 4 protein subunits: A, B, C, and L. Discrimination between the transferases can be based on the differences of the subunits in susceptibility to the inhibitors. The identification of transferase subunits is further supported by the combined use of specific substrates and inhibitors.

Animals↗
PubMed1983

Isolation and characterization of an anionic glutathione S-transferase from rat liver cytosol.

An anionic glutathione S-transferase representing approximately 20% of the total glutathione S-transferase protein and 10% of the total transferase activity toward 1-chloro 2,4-dinitrobenzene has been purified to homogeneity from the 105,000 x g supernatant of rat liver homogenate. The SDS gel electrophoretic data on subunit composition revealed that the anionic isozyme is composed of two subunits with an identical Mr of 26,000. The Km values for 1-chloro 2,4-dinitrobenzene and reduced glutathione were determined to be 0.94 mM and 0.23 mM respectively. A significant amount of glutathione peroxidase activity toward cumene hydroperoxide is associated with the new isozyme.

Animals↗
PubMed1984

Identification of a new glutathione S-transferase from rat liver cytosol.

A new glutathione S-transferase has been purified to homogeneity from 105,000 X g supernatant of Sprague-Dawley rat liver homogenates. The purified enzyme exhibited specific activities of approximately 1.8, and 0.12 mumoles X min-1 X mg-1 toward 1-chloro 2,4-dinitrobenzene and cumene hydroperoxide respectively. The SDS gel electrophoresis data on subunit composition revealed that the new transferase is composed of two subunits with an identical Mr of 24,400 (Y alpha Family). Our in vitro translation experiments with rat liver poly(A) RNAs and substrate specificity data suggest that this subunit is different from the previously reported Ya , Yb and Yc subunits of rat liver glutathione S-transferases. Comparatively, the new isozyme showed significant activity toward 1,2 epoxy-3-(P-nitrophenoxy)-propane, ethacrynic acid and P-nitrophenyl acetate, 0.4, 0.34 and 0.18 mumoles. min-1 X mg-1 respectively.

Animals↗
PubMed1985

Leukotriene C4 formation catalyzed by three distinct forms of human cytosolic glutathione transferase.

The ability of three distinct types of human cytosolic glutathione transferase to catalyze the formation of leukotriene C4 from glutathione and leukotriene A4 has been demonstrated. The near-neutral transferase (mu) was the most efficient enzyme with Vmax= 180 nmol X min-1 X mg-1 and Km= 160 microM. The Vmax and Km values for the basic (alpha-epsilon) and the acidic (pi) transferases were 66 and 24 nmol X min-1 X mg-1 and 130 and 190 microM, respectively. The synthetic methyl ester derivative of leukotriene A4 was somewhat more active as a substrate for all the three forms of the enzyme.

Arachidonic Acids↗
PubMed1987

The basic glutathione S-transferases from human livers are products of separate genes.

We have characterized a second cDNA sequence, pGTH2, for the human liver glutathione S-transferases Ha subunits. It is 95% homologous base-for-base to the Ha subunit 1 cDNA, pGTH1, except for its longer 3' noncoding sequences. Our results indicate that the multiple basic human liver glutathione S-transferases are products of separate genes. The proposal [Kamisaka, K., Habig, W. H., Ketley, J. N., Arias, I. M., and Jakoby, W. B. (1975) Eur. J. Biochem. 60, 153-161] that deamidation may be a physiologically important process for generating glutathione S-transferases isozyme multiplicity can be all but ruled out.

Amino Acid Sequence↗
PubMed1990

Induction of glutathione-S-transferase isoenzymes by protein A in rat liver.

The administration of Protein A, a cell wall protein of Staphylococcus aureus Cowan I cells, causes an induction of glutathione-s-transferase in rat liver. Proteins, cross reactive with anti human glutathione-s-transferase, acidic (pi), basic (alpha, and neutral (mu) isoenzymes, are induced by 5.8, 2.2 and 6.15 fold respectively. The induction of glutathione -s-transferases, at least in part, might play a role in manifestation of therapeutic properties of Protein A.

Animals↗
PubMed1991

Pig lens glutathione S-transferase belongs to class Pi enzyme.

Class Pi glutathione S-transferase was purified to homogeneity from pig lens cytosol. This enzyme was composed of two identical 22 kDa subunits and had isoelectric point of 8.5 from the results of SDS gel electrophoresis, gel filtration, amino acid sequence analysis and isoelectric focusing. Amino acid sequence of N-terminal 15 residues was almost identical to class Pi enzymes from human, rat and mouse. Antibody against the pig enzyme crossreacted to human glutathione S-transferase-pi and anti-rat glutathione S-transferase-P antibody crossreacted to pig enzyme.

Amino Acid Sequence↗
PubMed1991

The Drosophila glutathione S-transferase 1-1 is encoded by an intronless gene at 87B.

The Drosophila glutathione S-transferase 1-1 is a dimer of a 209 amino acid subunit, designated DmGST1. DmGST1 is encoded by a member of a multigene family. Sequence analysis of a genomic clone for GST1 revealed that it is encoded by an intronless gene. We designate this gene and its other family members the GST D genes in the glutathione S-transferase gene superfamily. The Drosophila GST D genes are mapped by in situ hybridization to chromosome 3R at 87B of the polytene chromosome, which is flanked by the two clusters of hsp70 genes at 87A7 and 87C1. Cytogenetic data in the literature indicated that a puff occurred in this region under heat shock. We report that the glutathione S-transferase activity in Kco cells as determined by conjugation with 1-chloro-2,4-dinitrobenzene is elevated slightly to two-fold under heat shock. The implication of this finding is discussed.

Amino Acid Sequence↗
PubMed1983

Induction of mouse liver glutathione S-transferase by ethanol.

The induction of hepatic glutathione S-transferase by ethanol was investigated in male Swiss-Webster mice using a liquid diet. After a 7-day feeding period, mice that received 18, 27 or 36% of their calories as ethanol exhibited significant increases in the specific activity of glutathione S-transferase when 1,2-dichloro-4-nitrobenzene (DCNB), p-nitrobenzylchloride (NBC) and 1,2-epoxy-3-(p-nitrophenoxy)propane (ENP) were used as substrates. The observed increases in activity appeared to be related to the concentration of ethanol in the diet. Thus, mice fed a diet with 36% of the calories as ethanol exhibited the greatest increase in specific activity (DCNB, 75%; NBC, 60%, ENP, 34%). Pair-fed mice demonstrated similar changes in enzymatic activity. A time-course study indicated a 4-day feeding period was not sufficient to elicit significant induction, but a significant increase was apparent by day 7. This increase was maintained or increased through day 14. By comparison, 0.5 mg of phenobarbital/ml of diet produced a greater increase in enzymatic activity (DCNB, 449%; NBC, 227%; ENP, 219%). These results suggest that ethanol does induce glutathione S-transferase, but it is a relatively poor inducer of this enzyme.

Animals↗
PubMed1984

Characterization of soluble glutathione transferase activity in resting mononuclear leukocytes from human blood.

Glutathione transferase activity in the soluble fraction of resting human mononuclear leukocytes was measured and characterized using [3H] trans-stilbene oxide as a substrate. Because of the low activity of this enzyme in these cells, a published assay procedure developed for rodent liver was slightly modified to improve its sensitivity: the substrate was highly radiolabeled (2 Ci/mmole) and carefully purified, and the incubation time was extended to 30-60 min. The activity measured was linear with cell density up to at least 6 million cells. Soluble glutathione transferase activity measured in this manner has a pH optimum around 7.4 and an optimal temperature of 40 degrees. This activity could be measured in lymphocytes, monocytes, granulocytes, erythrocytes and platelets, but not in plasma. From these measurements it could be calculated that lymphocytes account for somewhat more than half of the total activity in the mononuclear leukocyte fraction and that monocytes account for the rest. The intraindividual variation in soluble glutathione transferase activity towards trans-stilbene oxide in the mononuclear leukocyte fraction from different subjects was only about 10%, whereas the interindividual variation in this same activity was 15-fold. An explanation for this relatively large interindividual variation is now being sought.

Benzopyrene Hydroxylase↗
PubMed1985

Inhibition of Trypanosoma brucei brucei peptidyl transferase activity by sparsomycin analogs and effects on trypanosome protein synthesis and proliferation.

Peptidyl transferase activity of Trypanosoma brucei brucei polyribosomes was competitively inhibited by analogs of sparsomycin (Ki = 1-100 microM). The analogs were also potent inhibitors of [3H]-leucine and [3H]mannose incorporation into the proteins of intact trypanosomes with little or no effect on overall respiratory rate, suggesting a specific site of action for these analogs on protein synthesis. The peptidyl transferase inhibitors were effective at low concentrations at limiting the proliferation of trypanosomes both in vitro and in vivo. The potency of the compounds as inhibitors of cell proliferation was positively correlated with their efficacy as inhibitors of peptidyl transferase activity. One compound, MDL 20828 (1 mg/kg), increased the survival time of T. b. brucei-infected mice 4-fold in the absence of any overt drug toxicity to the hosts.

Acyltransferases↗
PubMed1985

Inhibition of purified rat liver glutathione S-transferase isozymes by diuretic drugs.

Seven soluble rat liver glutathione S-transferase isozymes were isolated and the inhibition of these isozymes by selected diuretics was investigated using 1-chloro-2,4-dinitrobenzene as substrate. All isozymes were inhibited to some extent under the experimental conditions used, but there was significant isozyme dependent selectivity of inhibition. The greatest inhibitory effect (over 80%) was found when the phenoxyacetic acid diuretics and indacrynic acid were incubated with glutathione S-transferase 3-3, 3-4 and 4-4. The sulphamoylbenzoic acid diuretics, furosemide and bumetanide, were found to have a lesser effect on the isozymes studies. As glutathione S-transferase are thought to play an important protective role in the various tissues of animals and man, by catalysing the glutathione conjugation of electrophilic drugs and drug metabolites, their inhibition may be toxicologically important.

Animals↗
PubMed1985

Inhibition by sulfasalazine of LTC synthetase and of rat liver glutathione S-transferases.

Sulfasalazine inhibited the formation of sulfidopeptide leukotrienes in ionophore A23187-challenged rat basophil leukemia cells in a dose-dependent fashion (EC50 = 0.11 mM). This compound also inhibited the solubilized, particulate LTC synthetase of RBL cells (EC50 = approximately 0.4 mM in the presence of a standard substrate mixture). The inhibition of LTC synthetase was paralleled by the capacity of sulfasalazine to potently inhibit several subfractions of the cytosolic rat liver glutathione S-transferases. The kinetics of the inhibition of the glutathione S-transferases, with 2,4-dinitrochlorobenzene as the substrate, were consistent with competitive inhibition with respect to glutathione (Ki values 0.21 +/- 0.05 to 0.46 +/- 0.096 microM in three discrete fractions). Inhibition with respect to the chromophoric substrate was uncompetitive in two of the three fractions examined (K'i values 0.61 +/- 0.13 and 1.05 +/- 0.14 microM) and non-competitive in the third (Ki = 0.72 microM). The inhibition of the LTC synthetase of RBL cells was also competitive with respect to glutathione (Ki = 120 microM). Both 5-aminosalicyclic acid and N'-2-pyridylsulfanilamide inhibited the one glutathione S-transferase fraction which was examined, and N'-2-pyridylsulfanilamide also inhibited the LTC synthetase. However, the kinetics of the inhibition of the liver enzyme by these compounds were not consistent with a competitive mechanism relative to glutathione, and the Ki values were at least 100 times greater than the ones for sulfasalazine on the same enzyme.

Animals↗
PubMed1988

Impairment of sulfobromophthalein biliary excretion and inhibition of glutathione S-transferase activity induced by perhexiline maleate in rats.

The effect of the antianginal agent perhexiline maleate (160 mg/kg i.g., daily for 4 days) on the biliary excretion of sulfobromophthalein (BSP) and BSP-glutathione and the hepatic activity of glutathione S-transferases was investigated in Wistar rats. Perhexiline maleate caused a significant reduction in the maximal biliary excretion of BSP (-28%). The decrease corresponded to a lowered excretion of the conjugated dye whereas the excretion of the parent compound did not change significantly. Administration of the drug caused no effect on the maximal biliary excretion of infused BSP-glutathione. Liver glutathione concentrations were similar in control and treated rats. Perhexiline maleate significantly reduced liver glutathione S-transferase activities toward BSP (-25%), 3,4-dichloronitrobenzene (DCNB) (-21%) and 1-chloro-3,4-dinitrobenzene (DNCB) (-27%). Kinetic studies of the enzyme in liver cytosol showed that perhexiline maleate induced an uncompetitive inhibition for the BSP substrate with a reduced Vmax and Km. The results indicate that the reduction in glutathione S-transferase activity plays an important role as a factor determining the impairment in the hepatobiliary transport of BSP caused by perhexiline maleate.

Animals↗
PubMed1990

Explanation of the non-hyperbolic kinetics of the glutathione S-transferases by the simplest steady-state random sequential Bi Bi mechanism.

We have demonstrated that the simplest steady-state random sequential Bi Bi mechanism is sufficient to explain the previously reported non-hyperbolic kinetics of glutathione S-transferase 3-3 [Pabst MJ et al., J Biol Chem 249: 7140-7150, 1974; Jakobson I et al., Biochem J 177: 861-868, 1979]. The metabolism of 1-chloro-2,4-dinitrobenzene by rat liver glutathione S-transferase isoenzymes 2-2 and 3-3 and of 1,2-dichloro-4-nitrobenzene by isoenzyme 3-4 was shown to exhibit non-hyperbolic kinetics, which are best fit by the simplest steady-state random sequential Bi Bi mechanism. Neither more complex steady-state mechanisms nor the superimposition of product inhibition or enzyme memory on the simplest steady-state mechanism was necessary to generate non-hyperbolic kinetics for the glutathione S-transferases.

Animals↗
PubMed1992

Metabolism of nitroglycerin by smooth muscle cells. Involvement of glutathione and glutathione S-transferase.

Metabolism of nitroglycerin (GTN) in the vascular smooth muscle is required for the drug to be effective in the treatment of angina pectoris and congestive heart failure. The usefulness of GTN is limited by the development of tolerance to the drug. The metabolism of GTN was studied in its target tissue, vascular smooth muscle. Inorganic nitrite was produced by cultured smooth muscle cells when GTN was added to the culture dish. Nitrite production increased with increasing GTN concentration and with incubation time. The enzymatic nature of GTN metabolism to nitrite was assessed by enzyme inhibition studies. Indocyanine green, a non-substrate inhibitor of glutathione S-transferase, inhibited GTN metabolism by smooth muscle cells. Cellular glutathione is also involved in GTN metabolism by the smooth muscle cell. Pretreatment with phorone, a glutathione S-transferase substrate, depleted cellular glutathione and decreased nitrite production from GTN. Pretreatment with buthionine sulfoximine, inhibitor of gamma-glutamylcysteine synthetase, decreased intracellular glutathione and caused decreased GTN metabolism in smooth muscle cells. Removal of cysteine from the smooth muscle cell incubation medium in combination with buthionine sulfoximine pretreatment decreased GTN metabolism to a lower level than buthionine sulfoximine pretreatment alone. This study shows that glutathione S-transferase and glutathione are involved in GTN metabolism by cultured smooth muscle cells.

Animals↗
PubMed1987

The role of glutathione and glutathione S-transferases in fatty acid ozonide detoxification.

The ozonide derived from methyl linoleate was shown to cause a dose dependent inhibition of the phagocytosis of rat alveolar macrophages exposed in vitro to concentrations varying from 10(-5) to 10(-4) M. Vitamin C was demonstrated to detoxify the ozonide. In analogy to their behaviour on exposure to ozone, vitamin E supplemented cells demonstrated a decreased and glutathione depleted cells an increased sensitivity towards the compound. The characteristics of antioxidant protection of cells against the ozonide were thus comparable to those for protection against ozone. Preincubation with glutathione also detoxified the ozonide model compound. Survival of rat alveolar macrophages exposed to a toxic concentration of the ozonide (86 microM final concentration), measured by phagocytosis of the cells, increased significantly (P less than 0.01) from 23 to 54% after a 2.5-h preincubation of the ozonide with glutathione (5 mM final concentration). The detoxification of methyl linoleate ozonide by glutathione could be catalyzed by the rat liver glutathione S-transferases. After a 2.5-h preincubation of the ozonide (86 microM final concentration) with glutathione and glutathione S-transferases (final concentrations, respectively, 5 mM and 0.01 mg/ml), its toxicity was completely abolished, as demonstrated by the 98% survival (P less than 0.001) of subsequently exposed cells. A Km(app) (at 1 mM glutathione) for the ozonide of 0.80 mM and a Vmax(app) (at pH 6.5) of 94 nmol glutathione converted X min-1 X mg protein-1 or (at pH 7.4) of 34 nmol glutathione converted X min-1 X mg protein-1, were found. This glutathione S-transferase catalyzed detoxification of the potential intermediates in ozone induced cell damage, offers a new viewpoint on the role of glutathione in the protection of cells against ozone.

Animals↗