© 1993 Oxford University Press
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Human glutathione S-transferase-expressing Salmonella typhimurium tester strains to study the activation/detoxification of mutagenic compounds: studies with halogenated compounds, aromatic amines and aflatoxin B1
Imperial Cancer Research Fund, Molecular Pharmacology Unit, Biomedical Research Centre, University of Dundee, Ninewells Hospital Dundee DD1 9SY, UK
1To whom correspondence should be addressed
We have developed Salmonella typhimurium strains expressing human glutathione S-transferases (GSTs) to establish the role of these enzymes in chemical activation and deactivation. Alpha and pl class GSTs, GSTA11 and GSTP11, were expressed in Salmonella TA100 using a regulatable tac promoter expression system. The ability of these GST to modulate the mutagenicity of a range of mutagens including ethylene dibromide, ethylene dichloride and methylene dichloride was then investigated. Ethylene dibromide, ethylene dichloride and methylene dichloride were directly mutagenic in the control TA100 strain. The mutagenicity of ethylene dibromide and ethylene dichloride was increased in cells expressing GSTA11, but not in cells expressing GSTP11. In contrast, methylene dichloride mutagenicity was unaffected by the presence of either GST. The mutagenicity of 2-aminofluorene, was not altered by the presence of either GST isozyme, while that of N-hydroxy-2-acetylaminofluorene was slightly reduced with both isozymes. The mutagenicity of aflatoxin B1 (AFB1) was marginally decreased in strains expressing GSTP11. When GSTA11 expression was maximally induced, however, a more pronounced reduction was observed suggesting a role for GSTA11 in AFB1 deactivation. The tester strains described here should be valuable in establishing the specificity of human GST isozymes towards chemical toxins and carcinogens, especially for compounds whose reactive intermediates are short lived.
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