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:2.5.1.18 (glutathione S-transferase)
22,582 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleotide sequence of the vaccinia virus open reading frame B1 predicts a polypeptide with significant sequence similarity to the catalytic domain of known protein kinases. To determine whether the B1R polypeptide is a protein kinase, we have expressed it in bacteria as a fusion with glutathione S-transferase. Affinity-purified preparations of the fusion protein were found to undergo autophosphorylation and also phosphorylated the exogenous substrates casein and histone H1. Mutation of lysine 41 to glutamine within the conserved kinase catalytic domain II abrogated protein kinase activity on all three protein substrates, supporting the notion that the protein kinase activity is inherent to the B1R polypeptide. Casein and histone H1 were phosphorylated on serine and threonine residues. The B1R fusion protein was phosphorylated on a threonine residue(s) by an apparently intramolecular mechanism. The autophosphorylation reaction resulted in phosphorylation of the glutathione S-transferase portion of the fusion and not the protein kinase domain. The protein kinase activity of B1R was specific for ATP as the phosphate donor; GTP was not utilized to a detectable extent. Immunoblotting experiments with anti-B1R antiserum showed that the protein kinase is located in the virion particle. Chromatography of virion extracts resulted in separation of the B1R protein kinase from the bulk of the total protein kinase activity, indicating that multiple protein kinases are present in the virion particle and that B1R is distinct from the previously described vaccinia virus-associated protein kinase.
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PMID:The vaccinia virus B1R gene product is a serine/threonine protein kinase. 156 May 22

Incubation of GST pi from human placenta with 8 mM PLP resulted in a rapid loss of activity during the first 10 min, concomitant with a Schiff base formation. This inactivation was probably due to the formation of a reversible adduct between PLP and the enzyme. After sodium borohydride treatment this adduct was reduced and stabilized. Stoichiometry and peptide isolation studies showed that three lysine residues were modified during reaction of GST and PLP. Protection of the enzyme against inactivation was achieved in the presence of 4 mM GSH suggesting that at least one lysyl residue is associated with the substrate binding site. Peptide mapping by digesting the enzyme with trypsin revealed that lysine shielded by GSH is Lys-127. Our results suggest that this residue may play an important role in enzymatic activity.
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PMID:Chemical modification of human placental glutathione transferase by pyridoxal 5'-phosphate. 159 39

A cDNA encoding a rat liver glutathione S-transferase Ya subunit has been expressed in Escherichia coli and the expressed enzyme purified to homogeneity. In order to examine the catalytic role of histidine in the glutathione S-transferase Ya homodimer, site-directed mutagenesis was used to replace all three histidine residues (at positions 8, 143, and 159) by other amino acid residues. The replacement of histidine 8 or histidine 143 with valine did not affect the 1-chloro-2,4-dinitrobenzene-conjugating activity nor the isomerase activity. However, the replacement of histidine with valine at position 159 produced the mutant GST which exhibited only partial activity. A greater decrease in catalytic activity was observed by histidine----tyrosine or histidine----lysine replacement at position 159. On the other hand, the histidine 159----asparagine mutant retained full catalytic activity. Our results indicate that histidine residues in the Ya homodimer are not essential for catalytic activity. However, histidine 159 might be critical in maintaining the proper conformation of this enzyme since replacement of this amino acid by either lysine or tyrosine did result in significant loss of enzymatic activity.
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PMID:Site-directed mutagenesis of glutathione S-transferase YaYa: nonessential role of histidine in catalysis. 189 79

7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity.
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PMID:Interaction of glutathione transferase from horse erythrocytes with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. 190 85

cDNA encoding the more acidic form, glutathione transferase (GST) psi, of the polymorphic Mu-class GSTs discovered in liver, was mutated in the 5'-end to create an NcoI site, facilitating cloning into the expression plasmid pKK233-2. The protein expressed from this construct has a point mutation Pro-2----Ala-2, but gives a catalytically functional protein. Back-mutation of the codon for amino acid residue 2 gave rise to a plasmid expressing the wild-type enzyme GST psi, or GST Mu1b-1b. A variant cDNA, differing only in specifying lysine rather than asparagine in position 173 of the coding region, was generated by site-directed mutagenesis. The variant sequence corresponds to another cDNA clone isolated from a human liver cDNA library and expresses the near-neutral GST mu, or GST Mu1a-1a. The two recombinant proteins GST Mu1a-1a and GST Mu1b-1b, by physicochemical as well as kinetic criteria, were found to be indistinguishable from GST mu and GST psi respectively, isolated from human liver. It is therefore concluded that the recombinant proteins correspond to the allelic variants observed in the human population. The two forms have different isoelectric points and correspond to the allelic variants observed in the human population. The two forms have different isoelectric points and their protein subunits can be separated by h.p.l.c. on a reverse-phase column. With standard substrates and inhibitors no differences in kinetic parameters between the two variants were detected. The mutated GST Mu1b-1b (Pro-2----Ala) was not significantly different in catalytic properties from the wild-type enzyme, even though Pro-2 is a well conserved amino acid residue in the known Mu-class GSTs.
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PMID:Heterologous expression of the allelic variant mu-class glutathione transferases mu and psi. 204 77

The glutathione S-transferases (GST) (glutathione transferase; EC 2.5.1.18) are a family of enzymes responsible for the metabolism of a broad range of xenobiotics and carcinogens. A cDNA clone containing the entire amino acid coding sequence of a human GST-2 subunit has been isolated using a lambda gt11 expression library. The complete nucleotide sequence and a partial restriction map are presented. The subunit is composed of 221 amino acids with a molecular weight of 25,425 before posttranslational modification. The deduced amino acid sequence is rich in lysine, which is consistent with the relatively high pI of GST-2. The human sequence shows considerable homology with the rat Ya and Yc GST sequences but little homology with the rat GSTp and Yb subunit sequences. Southern blots of restriction digests of human DNA indicate that there may be multiple GST-2 genes. In situ hybridization of the cloned cDNA to human chromosomes produces intense labeling only over band p12 on the short arm of chromosome 6 near the centromere. This indicates that the GST-2 gene(s) are located only at this site.
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PMID:Isolation of a cDNA clone and localization of human glutathione S-transferase 2 genes to chromosome band 6p12. 303 80

The effect of (1-benzoyl-1H-indazol-3-yl)oxylacetate L-Lysine (bendazac-lysine) on some enzymatic activities involved in the metabolism of reduced glutathione (GSH) was studied in the rabbit lens during developing cataract induced by a single dose of X-rays (2000 rads). The specific activities of glutathione reductase (G.R.), glutathione peroxidase (GSH.Px) and glutathione S-transferase (GSHS-tr.) do not change following irradiation and treatment with bendazac-lysine. The activity of the same enzymes expressed as a function of water soluble proteins (WSP) per lens significantly decreases (P less than 0.01) as compared to controls in the irradiated lens not treated with bendazac-lysine (ILNTB) at the 8th week, whereas no significant decrease as compared to controls is observed in the irradiated lens treated with bendazac-lysine (ILTB). In the ILNTB the specific activity of glucose-6-phosphate dehydrogenase (G6PDH) is reduced by 10% after 0.3 weeks and by 29% after 12 weeks. In the ILTB the specific activity of G6PDH is reduced by 8% after 0.3 weeks and by 14.5% after 12 weeks. The specific activity of superoxide dismutase (SOD) in the ILNTB is reduced by 19% after 0.3 weeks and reached 31% after 12 weeks. In the ILTB the specific activity of SOD is reduced by 11% after 0.3 weeks and 19.8% after 12 weeks. The mechanism of protective effect of bendazac-lysine on cataract is discussed.
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PMID:Effects of bendazac L-lysine salt on some metabolic enzymes of glutathione in the rabbit lens after X-irradiation. 361 May 98

A study of the structure of glutathione transferase B (ligandin) has been made with a view to understanding the relationship between the structures of the subunits of which it is composed. It consists of a mixture of a homodimer (YaYa) and a heterodimer (YaYc) in which the monomers are defined by their apparent molecular weights, that of Ya being 22000 and Yc 25000. Soluble tryptic peptides from the native homodimer YaYa have been compared with those from an artificial homodimer YcYc produced by rehybridization of native YaYc. Approximately 10 peptides specific to YaYa, 12 specific to YcYc and 21 common to both have been detected. Some of the above peptides are derived from variants of the monomers themselves. YaYa and YcYc have two C termini which are the same in both dimers, namely phenylalanine and lysine. Also there are four cysteinyl peptides, of which three are common to YaYa and YcYc and one specific to each. These results suggest that Ya and Yc are derived from at least two different but related genes.
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PMID:Evidence that the Ya and Yc subunits of glutathione transferase B (ligandin) are the products of separate genes. 714 Jul 37

The Ste20p protein kinase was immunopurified from yeast cells and analyzed in an in vitro assay system. Ste20p immune complexes exhibited autophosphorylating activity at serine and threonine residues and specifically phosphorylated a bacterially expressed glutathione S-transferase (GST) fusion of Ste11p (a mitogen-activated protein or extracellular signal-regulated kinase kinase (MEK) kinase homologue) at serine and threonine residues. In contrast, GST fusions either of Ste7p (a MEK homologue) or the beta-subunit of the mating response G-protein and immunoprecipitated Ste5p were not phosphorylated by the Ste20p immune complexes. Myelin basic protein was identified as an excellent in vitro substrate, whereas histone H1 was only poorly phosphorylated. Evidence was obtained that autophosphorylation might play a regulatory role for the in vitro kinase activity. The in vitro activity was found to be Ca(2+)-independent. Both the in vivo and in vitro activities were abolished by mutational changes of either the conserved lysine residue 649 within the ATP binding site or threonine 777 between the catalytic subdomains VII and VIII. Wild-type Ste20p and the catalytically inactive T777A mutant were identified as phosphoproteins in vivo. The phosphorylation occurred at serine and threonine residues independent of pheromone stimulation. Based on the genetically determined significance of Ste20p in pheromone signal transduction and on our in vitro studies, we propose the model that Ste20p represents a yeast MEK kinase kinase whose function is to link G-protein-coupled receptors through G beta gamma to a mitogen-activated protein kinase module.
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PMID:Molecular characterization of Ste20p, a potential mitogen-activated protein or extracellular signal-regulated kinase kinase (MEK) kinase kinase from Saccharomyces cerevisiae. 760 57

The recognition of lysosomal enzymes by UDP-GlcNAc: lysosomal-enzyme GlcNAc-1-phosphotransferase (phosphotransferase) is mediated by a protein structure on lysosomal enzymes. It has been previously demonstrated that lysine residues are required for phosphorylation of procathepsin L and are a common feature of the site on many lysosomal proteins. In this work, the procathepsin L recognition structure was further defined by identification of the region of the protein containing the structure and the critical lysine residues involved. Removal of the cathepsin L propeptide by low pH-induced autocatalytic processing abolished phosphorylation. The addition of either the purified propeptide or a glutathione S-transferase-propeptide fusion protein to the processed protein restored phosphorylation. Mutagenesis of individual lysine residues demonstrated that two propeptide lysine residues (Lys-54 and Lys-99) were required for efficient phosphorylation of procathepsin L. By comparison of the phosphorylation rates of procathepsin L, lysine-modified procathepsin L, and the procathepsin L oligosaccharide, lysine residues were shown to account for most, if not all, of the protein-dependent interaction. On this basis, it is concluded that the proregion lysine residues are the major elements of the procathepsin L recognition site. In addition, lysine residues in cathepsin D were shown to be as important for phosphorylation as those in procathepsin L, supporting a general model of the recognition site as a specific three-dimensional arrangement of lysine residues exposed on the surface of lysosomal proteins.
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PMID:Lysine-based structure in the proregion of procathepsin L is the recognition site for mannose phosphorylation. 779 59


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