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Sökning: WFRF:(Mannervik Bengt) > (1980-1989) > (1988)

  • Resultat 1-4 av 4
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  • Danielson, U Helena, et al. (författare)
  • Paradoxical inhibition of rat glutathione transferase 4-4 by indomethacin explained by substrate-inhibitor-enzyme complexes in a random-order sequential mechanism
  • 1988
  • Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 250:3, s. 705-711
  • Tidskriftsartikel (refereegranskat)abstract
    • Under standard assay conditions, with 1-chloro-2,4-dinitrobenzene (CDNB) as electrophilic substrate, rat glutathione transferase 4-4 is strongly inhibited (I50 = 1 microM) by indomethacin. No other glutathione transferase investigated is significantly inhibited by micromolar concentrations of indomethacin. Paradoxically, the strong inhibition of glutathione transferase 4-4 was dependent on high (millimolar) concentrations of CDNB; at low concentrations of this substrate or with other substrates the effect of indomethacin on the enzyme was similar to the moderate inhibition noted for other glutathione transferases. In general, the inhibition of glutathione transferases can be explained by a random-order sequential mechanism, in which indomethacin acts as a competitive inhibitor with respect to the electrophilic substrate. In the specific case of glutathione transferase 4-4 with CDNB as substrate, indomethacin binds to enzyme-CDNB and enzyme-CDNB-GSH complexes with an even greater affinity than to the corresponding complexes lacking CDNB. Under presumed physiological conditions with low concentrations of electrophilic substrates, indomethacin is not specific for glutathione transferase 4-4 and may inhibit all forms of glutathione transferase.
  • Mannervik, Bengt, et al. (författare)
  • Glutathione transferases - structure and catalytic activity
  • 1988
  • Ingår i: Crc Critical Reviews in Biochemistry. - 0045-6411. ; 23:3, s. 283-337
  • Tidskriftsartikel (refereegranskat)abstract
    • The glutathione transferases are recognized as important catalysts in the biotransformation of xenobiotics, including drugs as well as environmental pollutants. Multiple forms exist, and numerous transferases from mammalian tissues, insects, and plants have been isolated and characterized. Enzymatic properties, reactions with antibodies, and structural characteristics have been used for classification of the glutathione transferases. The cytosolic mammalian enzymes could be grouped into three distinct classes--Alpha, Mu, and Pi; the microsomal glutathione transferase differs greatly from all the cytosolic enzymes. Members of each enzyme class have been identified in human, rat, and mouse tissues. Comparison of known primary structures of representatives of each class suggests a divergent evolution of the enzyme proteins from a common precursor. Products of oxidative metabolism such as organic hydroperoxides, epoxides, quinones, and activated alkenes are possible "natural" substrates for the glutathione transferases. Particularly noteworthy are 4-hydroxyalkenals, which are among the best substrates found. Homologous series of substrates give information about the properties of the corresponding binding site. The catalytic mechanism and the active-site topology have been probed also by use of chiral substrates. Steady-state kinetics have provided evidence for a "sequential" mechanism.
  • Principato, Giovanni B, et al. (författare)
  • Relaxed thiol substrate specificity of glutathione transferase effected by a non-substrate glutathione derivative
  • 1988
  • Ingår i: FEBS Letters. - 0014-5793 .- 1873-3468. ; 231:1, s. 155-158
  • Tidskriftsartikel (refereegranskat)abstract
    • Rat glutathione transferase 4-4 catalysed the conjugation of 2-mercaptoethanol with 1-chloro-2,4-dinitrobenzene in the presence of S-methyl-glutathione. The reaction was linearly dependent on enzyme concentration and saturation was seen with respect to both 2-mercaptoethanol and S-methyl-glutathione concentration. High concentrations of S-methyl-gluta-thione were inhibitory. The results suggest that the natural substrate glutathione has two distinct functions in the normal catalytic reaction, (i) induction of a catalytically competent conformation of the enzyme and (ii) provision of the substrate sulfhydryl group in the reaction catalyzed.
  • Söderström, Mats, et al. (författare)
  • Leukotriene C synthase in mouse mastocytoma cells. An enzyme distinct from cytosolic and microsomal glutathione transferases
  • 1988
  • Ingår i: Biochemical Journal. - : Portland Press. - 0264-6021 .- 1470-8728. ; 250:3, s. 713-718
  • Tidskriftsartikel (refereegranskat)abstract
    • Leukotriene C4 synthesis was studied in preparations from mouse mastocytoma cells. Enzymic conjugation of leukotriene A4 with glutathione was catalysed by both the cytosol and the microsomal fraction. The specific activity of the microsomal fraction (7.8 nmol/min per mg of protein) was 17 times that of the cytosol fraction. The cytosol fraction of the mastocytoma cells contained two glutathione transferases, which were purified to homogeneity and characterized. A microsomal glutathione transferase was purified from mouse liver; this enzyme was shown by immunoblot analysis to be present in the mastocytoma microsomal fraction at a concentration one-tenth or less of that in the liver microsomal fraction. Both the cytosolic and the microsomal glutathione transferases in the mastocytoma cells were identified with enzymes previously characterized, by determining specific activities with various substrates, sensitivities to inhibitors, reactions with antibodies, and physical properties. The purified microsomal glutathione transferase from liver was inactive with leukotriene A4 or its methyl ester as substrate. The cytosolic enzymes displayed activity with leukotriene A4, but their specific activities and intracellular concentrations were too low to account for the leukotriene C4 formation in the mastocytoma cells. The microsomal fraction of the cells contained an enzyme distinguishable by various criteria from the previously studied glutathione transferases. This membrane-bound enzyme, leukotriene C synthase (leukotriene A4:glutathione S-leukotrienyltransferase), appears to carry the main responsibility for the biosynthesis of leukotriene C4.
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  • Resultat 1-4 av 4
Typ av publikation
tidskriftsartikel (4)
Typ av innehåll
refereegranskat (4)
Mannervik, Bengt (4)
Danielson, U. Helena (3)
Söderström, Mats (1)
Hammarström, Sven (1)
Principato, Giovanni ... (1)
Uppsala universitet (3)
Linköpings universitet (1)
Engelska (4)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (2)

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