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)

Human muscle glutathione S-transferase isozyme, GST zeta (pI 5.2) has been purified by three different methods using immunoaffinity chromatography, DEAE cellulose chromatography, and isoelectric focusing. GST zeta prepared by any of the three methods does not recognize antibodies raised against the alpha, mu, or pi class glutathione S-transferases of human tissues. GST zeta has a blocked N-terminus and its peptide fingerprints also indicate it to be distinct from the alpha, mu, or pi class isozymes. As compared to GSTs of alpha, mu, and pi classes, GST zeta displays higher activities toward t-stilbene oxide and Leukotriene A4 methyl ester. GST zeta also expresses GSH-peroxidase activity toward hydrogen peroxide. The Kms of GST zeta for CDNB and GSH were comparable to those reported for other human GSTs but its Vmax for CDNB, 7620 mol/mol/min, was found to be considerably higher than that reported for other human GSTs. The kinetics of inhibition of GST zeta by hematin, bile acids, and other inhibitors also indicate that it was distinct from the three classes of GST isozymes. These studies suggest that GST zeta corresponds to a locus distinct from GST1, GST2, and GST3 and probably corresponds to the GST4 locus as suggested previously by Laisney et al. (1984, Human Genet. 68, 221-227). The results of peptide fingerprints and kinetic analysis indicate that as compared to the pi and alpha class isozymes, GST zeta has more structural and functional similarities with the mu class isozymes. Besides GST zeta several other GST isozymes belonging to pi and mu class have also been characterized in muscle. The pi class GST isozymes of muscle have considerable charge heterogeneity among them despite identical N-terminal sequences.
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PMID:Purification and characterization of human muscle glutathione S-transferases: evidence that glutathione S-transferase zeta corresponds to a locus distinct from GST1, GST2, and GST3. 184 34

An acidic glutathione S-transferase (GST) isoenzyme termed GST6 has been isolated from human brain, characterized and compared with other isoenzymes. The N-terminal amino acid sequence of GST6 was found to be identical with that of GST4 previously purified from human muscle. GST6 cross-reacted with antibody raised against GST4, but not with antisera raised against GST1, GST2 or GST3. The subunit Mr and pI of GST6 were found to be different from those of GST4. The present results indicate that GST6 is another member of the Mu evolutionary class which in man also includes GST1, GST4 and GST5. A minor component that co-purified with GST6 was shown to have an N-terminal sequence similar to, but not identical with, that of GST3. This isoenzyme may be an additional member of the Pi evolutionary class.
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PMID:Purification and characterization of acidic glutathione S-transferase 6 from human brain. 200 8

Glutathione transferase (GST) epsilon (also known as GST2 or GST B1B1), the major Class Alpha GST in human liver has been subjected to oligonucleotide-directed site-specific mutagenesis. Four arginine residues, R13, R20, R69 and R187, of which all but R69 are strictly conserved through GST Classes Alpha, Mu and Pi have been replaced by Ala. The mutant enzymes have been expressed in Escherichia coli, purified by affinity chromatography and characterised. Compared with the wild-type enzyme, all mutant GSTs had altered catalytic properties. All mutants had decreased specific activity with 1-chloro-2,4-dinitrobenzene (CDNB). Mutants R13A, R69A and R187A also showed decreased activities with other substrates such as cumene hydroperoxide (CuOOH) and androstenedione. In contrast, mutant R20A had an increased peroxidase activity and an isomerase activity essentially the same as that of the wild-type GST. With the substrates used, kcat./Km values were decreased for all mutant GSTs. Increases in the [S0.5] values were most significant for glutathione (GSH), while values for CDNB and CuOOH were less markedly affected. Thus, various kinetic data indicate that the GSH affinity has been reduced by the mutations and that this loss of affinity is linked to the decreased specific activities. Inhibition studies showed an increased sensitivity towards S-hexyl-GSH; this was particularly marked for mutant R69A. Mutant R20A had a lowered [I50] value but, in contrast, also the highest [I80] value as compared with the wild-type enzyme. Towards bromosulphophthalein, mutants R20A and R69A had a markedly increased sensitivity, about 35-fold in comparison with the wild-type. The inhibition properties of mutant R187A were similar to those of the wild-type enzyme and the properties of mutant R13A were in between. The increased sensitivity to S-hexyl-GSH, in contrast with the decreased affinity for GSH, was suggested to be due to an altered distribution between conformational states of the enzyme induced by the mutations. The arginine residues in positions 13, 20 and 69 all seem to be important for the catalytic properties of GST. Further, the inhibition studies indicate a role of arginine residues in the stabilisation of conformational states of the enzyme.
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PMID:Effects of directed mutagenesis on conserved arginine residues in a human Class Alpha glutathione transferase. 200 17

A plasmid vector was constructed that encodes the expression in Escherichia coli of a truncated form of GST2, a human Alpha-class glutathione transferase. The truncated enzyme, GST2del210, has 12 residues deleted from the C-terminus and has the last two residues of the new C-terminal mutated from aspartic acid and glutamic acid to histidine and glycine respectively. GST2del210 has substantially diminished specific activity with either 1-chloro-2,4-dinitrobenzene or cumene hydroperoxide as substrate. The affinity of the truncated enzyme for a GSH-agarose matrix was also diminished, but sufficient interaction remained to enable affinity purification. Inhibition of GST2del210 by bromosulphophthalein was not altered. In contrast, this truncated form was not inhibited by S-pentylglutathione, a competitive inhibitor of the wild-type GST2 isoenzyme. The results show that the C-terminal segment of the Alpha-class glutathione transferases may form a component of the hydrophobic substrate-binding site. In contrast, this region appears not to be directly involved in GSH binding and is not absolutely essential for catalytic activity.
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PMID:The contribution of the C-terminal sequence to the catalytic activity of GST2, a human alpha-class glutathione transferase. 201 73

Multiple human cytosolic glutathione transferases have been described. These enzymes are the products of multiple genes that can be classified into at least four evolutionary classes. The genes encoding each class appear to be clustered on distinct chromosomes. Over-expression of glutathione S-transferase (GST) isoenzymes has been implicated in drug resistance and, conversely, deficiency of GST isoenzymes has been implicated in susceptibility to carcinogens. Some GST genes are expressed at varying levels in different individuals, and there is a frequent deficiency of the Mu class GST1 isoenzyme in all the racial groups studied so far. This deficiency is due to a deletion of the GST 1 gene. The Alpha class genes are located on the short arm of chromosome 6 and are closely linked, with less than 2 kb separating some genes. There is evidence for the existence of several pseudogenes in this cluster. A complete Alpha class gene has 7 exons and extends over 13 kb. The 5' flanking region of the gene encoding the GST2 type 1 isoenzyme has been cloned and sequenced. This region contains a number of putative promoter and enhancer elements that are similar to those found in rat and mouse Alpha class genes.
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PMID:Molecular genetics of the human glutathione S-transferase. 213 79

The products of three human glutathione S-transferase (RX:glutathione R-transferase, EC 2.5.1.18) (GST) loci (GST 1, GST 2 and GST 3) were purified and their immunohistochemical localization in liver was studied with special attention to the polymorphism of GST1 (neutral isozyme). The GST1 was homogeneously stained in cytoplasm of hepatocytes throughout the lobule of liver showing GST1 1, GST1 2 and GST1 2-1 phenotypes. However, none of the hepatic tissue showing GST1 0 phenotype was stained. Immunohistochemical staining of GST2 (basic isozyme) was distributed in the cytoplasm of hepatocytes homogeneously throughout the hepatic lobule in all cases and the strong staining intensity was also demonstrated in nucleus. GST3 (acidic isozyme) was strongly stained in biliary epithelium, while staining of hepatocytes was not apparent. These results indicate that the human liver GST isozymes exhibit significant difference in their inter-individual, specific cellular and organellar distribution.
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PMID:Immunohistochemical localization of human liver glutathione S-transferase (GST) isozymes with special reference to polymorphic GST1. 246 63

Glutathione S-transferases (GST; E.C.2.5.1.18) were phenotyped by starch gel electrophoresis in post-mortem liver samples from 683 unrelated subjects of both sexes. 305 were Chinese, 185 Indians, 147 Malays and 46 from other racial groups of South-East Asia. GST1 and GST2 were found to be polymorphic in these populations. Additional alleles (GST1*3 and GST2*O) were observed at low frequency in all the ethnic groups. The frequency of GST1*1 was lower and that of GST1*2 was higher in Indians and Malays as compared to Chinese. GST1*0 and GST1*3 frequencies were similar in all these ethnic groups. The gene frequencies of the alleles of the GST2 locus varied significantly in the population studied. GST2*0 frequency was significantly higher in Indians than in Chinese and Malays, while the lowest frequency of GST2*1 was found in the Indians. GST2*2 frequency was higher in the Malays than in Chinese and Indians. GST1 and GST2 phenotype distributions were in agreement with Hardy-Weinberg equilibrium in all the ethnic groups studied. Sex made no significant difference in the phenotype distribution.
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PMID:Glutathione-S-transferase (GST) polymorphism among ethnic groups in Singapore with report of additional alleles at loci 1 and 2. 248 53

The products of three human glutathione S-transferase (GST) loci (GST1, GST2 and GST3) were purified and their immunochemical properties as well as immunohistological localization in liver were studied. Three group of isozymes were different in molecular weight, substrate specificities and antigenicity. Two homodimers (type 1 and type 2) of GST1 which shows genetic polymorphism, were similar in immunochemical properties other than isoelectric point. Inactivity of GST1 0 was due to impaired protein synthesis. Immunohistologically, GST1 isozyme was homogeneously stained in cytoplasm of hepatocytes throught the lobule of liver showing GST1 1, GST1 2 and GST1 2-1 phenotypes. On the other hand, GST2 isozyme was stained in the cytoplasm as well as the nucleus of hepatocytes throughout the hepatic lobule in all cases. GST3 isozyme was strongly stained in biliary epithelium. These results indicate that the human liver GSTs are composed of three immunochemically distinct isozymes, which exhibit significant difference in inter-individual, specific cellular and organellar distribution.
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PMID:[Immunochemical properties and immunohistological localization of human liver glutathione S-transferase isozymes]. 262 19

Single crystals of human GST2, a class alpha glutathione transferase have been grown in polyethylene glycol 2000 by the hanging-drop vapour diffusion method. The crystals belong to space group C2 and have cell dimensions a = 100.8 A, b = 95.4 A, c = 105.2 A and beta = 92.4 degrees. The X-ray diffraction pattern extends to better than 3 A resolution.
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PMID:Crystallization of GST2, a human class alpha glutathione transferase. 276 66

Several forms of glutathione S-transferase (GST) are present in human kidney, and the overall isoenzyme pattern of kidney differs significantly from those of other human tissues. All the three major classes of GST isoenzymes (alpha, mu and pi) are present in significant amounts in kidney, indicating that GST1, GST2 and GST3 gene loci are expressed in this tissue. More than one form of GST is present in each of these classes of enzymes, and individual variations are observed for these classes. The structural, immunological and functional properties of GST isoenzymes of three classes differ significantly from each other, whereas the isoenzymes belonging to the same class have similar properties. All the cationic GST isoenzymes of human kidney except for GST 9.1 are heterodimers of 26,500-Mr and 24,500-Mr subunits. GST 9.1 is a dimer of 24,500-Mr subunits. All the cationic isoenzymes of kidney GST cross-react with antibodies raised against a mixture of GST alpha, beta, gamma, delta and epsilon isoenzymes of liver. GST 6.6 and GST 5.5 of kidney are dimers of 26,500-Mr subunits and are immunologically similar to GST psi of liver. Unlike other human tissues, kidney has at least two isoenzymes (pI 4.7 and 4.9) associated with the GST3 locus. Both these isoenzymes are dimers of 22,500-Mr subunits and are immunologically similar to GST pi of placenta. Some of the isoenzymes of kidney do not correspond to known GST isoenzymes from other human tissues and may be specific to this tissue.
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PMID:Purification and characterization of glutathione S-transferases of human kidney. 311 68


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