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- Sundberg, K, et al.
(författare)
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Studies on the differential inhibition of glutathione conjugate formation of (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide and 1-chloro-2,4-dinitrobenzene in V79 Chinese hamster cells
- 2000
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Ingår i: The Biochemical journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 349349 Pt 3, s. 693-696
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Tidskriftsartikel (refereegranskat)abstract
- V79 Chinese hamster cells have previously been shown to lack the capacity to detoxify the mutagenic and carcinogenic compound (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide [(+)-anti-BPDE] by Pi class glutathione transferase (GSTPi)-catalysed conjugation with GSH, although these cells contain such an enzyme [Romert, Dock, Jenssen and Jernström (1989) Carcinogenesis 10, 1701–1707; Swedmark, Romert, Morgenstern and Jenssen (1992) Carcinogenesis 13, 1719–1723; Swedmark and Jenssen (1994) Gene 139, 251–256]. Previous findings also indicate that these results do not depend on an inactive GSTPi enzyme, since V79 cells conjugate 1-chloro-2,4-dinitrobenzene (CDNB) with GSH, but more likely on (a) factor(s) that inhibit(s) V79 GSTPi selectively [Swedmark, Jernström and Jenssen (1996) Biochem. J. 318, 533–538]. The present study demonstrates that both human and V79 recombinant GSTPi enzymes are inhibited with respect to conjugating (+)-anti-BPDE, but not CDNB, after pre-incubation with V79-cell extract, but not with MCF-7-cell extract. In addition, it was found that the inhibition is dependent on the amount of cell extract present and that the factor(s) is heat-resistant and has a molecular mass of less than 10 kDa, suggesting that the factor(s) is (are) non-proteinaceous in nature.
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- Swedmark, S, et al.
(författare)
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Comparison of the mRNA sequences for Pi class glutathione transferases in different hamster species and the corresponding enzyme activities with anti-benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide
- 1996
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Ingår i: The Biochemical journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 318318 ( Pt 2), s. 533-538
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Tidskriftsartikel (refereegranskat)abstract
- Glutathione S-transferase (GST) of class Pi (GST Pi) is known to detoxify the mutagenic and carcinogenic (+)-anti-benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide [(+)-anti-BPDE] by conjugation with glutathione. Previously, we have shown that Chinese hamster V79 cells contain GST Pi, but seem to lack the capacity to conjugate (+)-anti-BPDE, although these cells do conjugate other substrates with GSH [Romert, Dock, Jenssen and Jernström (1989) Carcinogenesis 10, 1701–1707; Swedmark, Romert, Morgenstern and Jenssen (1992) Carcinogenesis 13, 1719–1723; Swedmark and Jenssen (1994) Gene 139, 251–256]. In the present study we have compared four cell lines derived from different hamster species with respect to GST cDNA sequences and capacity to conjugate (+)- or (-)-anti-BPDE. The cell lines were V79 and Chinese hamster ovary cells (CHO), Armenian hamster lung (AHL) cells and baby hamster kidney (BHK) cells. The sequencing revealed a complete homology between the V79 and CHO cDNA for GST Pi, whereas the corresponding amino acid sequences predicted from the corresponding AHL and BHK cDNAs differed by six and nine amino acids, respectively, from the predicted V79 sequence. None of these changes alone was found to influence the xenobiotic substrate-binding site. The cytosolic fractions from BHK and AHL cells were found to catalyse conjugation of (+)-anti-BPDE with GSH, whereas the corresponding activity in CHO cells was non-detectable. As shown previously, V79 cells were devoid of activity towards (+)-anti-BPDE. All the cell lines studied demonstrated appreciable GST activity towards 1-chloro-2,4-dinitrobenzene, but no activity with (-)-anti-BPDE. The latter result suggests that GST Pi is the sole or predominant GST in these cell lines. This was confirmed by HPLC analysis of purified enzymes obtained by affinity chromatography. However, when the catalytic activities of the pure enzymes were determined, all four different GST Pi enzymes were found to be highly capable of conjugating (+)-anti-BPDE with GSH. This observation indicates the existence of an intracellular factor that selectively inhibits conjugation of (+)-anti-BPDE, but not of 1-chloro-2,4-dinitrobenzene in the V79 and CHO cell lines. This new phenomenon seems to be specific for Chinese hamster, since both these cell lines originate from this species.
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