| 2. |
- Castro, Victor M, et al.
(författare)
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Differences among human tumor cell lines in the expression of glutathione transferases and other glutathione-linked enzymes
- 1990
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Ingår i: Carcinogenesis. - : Oxford University Press. - 0143-3334 .- 1460-2180. ; 11:9, s. 1569-1576
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Tidskriftsartikel (refereegranskat)abstract
- A large number of human tumor cell lines of various origins have been investigated with respect to expression of glutathione-linked enzymes in the cytosol fraction. The amounts of the different enzymes were estimated by use of activity measurements and by silver staining or immunoblot analysis after electrophoresis of cytosol fractions purified by affinity chromatography on S-hexylglutathione Sepharose. Class Pi glutathione transferase was the most abundant enzyme in most tumor cells; the cell lines HepG2 and Raji were exceptions in not expressing significant amounts of this enzyme. HepG2 cells derive from hepatocytes, which normally do not express the class Pi enzyme, whereas Raji cells originate from B-lymphocytes, which normally do express a class Pi glutathione transferase. The highest level of the class Pi transferase, in terms of protein reacting with antibodies as well as enzyme activity, was noted in the colon carcinoma cell line LS174T. Hu549Pat cells, EBV-transformed B-lymphocytes, also expressed high levels of a protein reacting with antibodies specific for class Pi glutathione transferases, but did not display any significant activity with ethacrynic acid, a substrate characteristic for this class. Class Alpha and class Mu glutathione transferases, in cell lines expressing these isoenzymes, were present in significantly lower concentrations than the class Pi enzyme. Most of the tumor cells contained a class Alpha transferase composed of 27.5 kd subunits, which has the physicochemical and immunological properties of the most basic glutathione transferase found in human skin. In several cell lines, a protein was detected with an apparent subunit Mr value of 30 kd that was tentatively identified as an additional class Alpha glutathione transferase not previously described. In addition, other glutathione-linked enzyme activities, namely glutathione peroxidase, glutathione reductase and glyoxalase I, were assayed with specific substrates in the cytosolic fraction of the tumor cells; glyoxalase I could also be estimated semiquantitatively by silver staining of SDS-PAGE cells after affinity chromatography. Like the glutathione transferases, these enzymes displayed distinctly different levels of expression in the various cell lines. Thus, virtually every cell line was found to have a unique pattern of glutathione-linked enzymes, suggesting that the resistance phenotypes of the cells differ accordingly.
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| 3. |
- Söderström, Mats, et al.
(författare)
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Leukotriene C4 synthase : characterization in mouse mastocytoma cells
- 1990
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Ingår i: Methods in Enzymology. - : Elsevier. - 0076-6879 .- 1557-7988. ; 187, s. 306-312
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Tidskriftsartikel (refereegranskat)abstract
- The chapter presents a study on leukotriene C4 (LTC4) synthase, discussing the characterization in mouse mastocytoma cells. LTC4 is formed by conjugation of leukotriene A4 (LTA4) with glutathione (GSH). In biological systems, the reaction is catalyzed by a membrane-bound enzyme, leukotriene C4 synthase (EC 2.5.1.37). Cytosolic glutathione transferases, in particular, members of the class Mu, have been shown to catalyze formation of LTC4.The most efficient isoenzymes are transferase 6-6 isolated from rat brain, transferase 4-4 from rat liver, and transferase μ from human liver. The name leukotriene C4 synthase, used for the enzyme described in this chapter, has been adopted to distinguish the enzyme from the above glutathione transferases, which display broad substrate specificity. Reports from three groups of investigators have shown that LTC4 formation in rat basophilic leukemia cells is catalyzed by a membrane-bound enzyme. Leukotriene C4 synthase activity has been described and an enzyme partially purified from the microsomal fraction of guinea pig lung. The formation of LTC4 is especially high in mouse mastocytoma cells, the source from which LTC4 was first isolated. The partial purification of leukotriene C4 synthase from this source is described in the chapter.
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