0000000000381378
AUTHOR
Ulrike Pabel
Sulfotransferase-mediated activation of mutagens studied using heterologous expression systems
Abstract Sulfation is a common final step in the biotransformation of xenobiotics and is traditionally associated with inactivation. However, the sulfate group is electron-withdrawing and may be cleaved off heterolytically in some molecules leading to electrophilic cations which may form adducts with DNA and other important cellular structures. Since endogenous sulfotransferases do not appear to be expressed in indicator cells of standard mutagenicity tests, rat and human sulfotransferases have been stably expressed in his−Salmonella typhimurium strain TA1538 and Chinese hamster V79 cells. Using these recombinant indicator cells, sulfotransferase-dependent genotoxic activities were detected…
Activation of propane 2-nitronate to a genotoxicant in V79-derived cell lines engineered for the expression of rat hepatic sulfotransferases
2-Nitropropane (2-NP) is a genotoxic hepatocarcinogen in rats. The genotoxicity of the compound has been attributed to a sulfotransferase-mediated formation of DNA-reactive species from the anionic form of 2-NP, propane 2-nitronate (P2N). Several observations have suggested that sulfotransferases (SULTs) 1A1 and/or 1C1 may be important in the activation of P2N to a genotoxicant in rat liver, but a definite proof is lacking. In order to identify the sulfotransferase(s) of rat liver that are capable of activating P2N, we have investigated the genotoxicity of P2N in various V79-derived cell lines engineered for expression of individual forms of rat hepatic sulfotransferases. Genotoxicity was a…
Chiral Inversion of 1-Hydroxyethylpyrene Enantiomers Mediated by Enantioselective Sulfotransferases
The benzylic alcohol 1-hydroxyethylpyrene (1-HEP) is activated to a mutagen by sulfotransferases. The sulfuric acid ester formed is difficult to detect, as it is rapidly hydrolysed back to the alcohol. Incubation of the individual enantiomers of 1-HEP with human hydroxysteroid sulfotransferase (hHST) or estrogen sulfotransferase (hEST), expressed in bacteria, led to the formation of the other enantiomer. The rates of sulfation were determined from the initial rates of chiral inversion of the alcohol, knowing that hydrolysis follows an SN1 mechanism and therefore produces racemic alcohol. hEST showed high enantioselectivity for S-1-HEP, whereas hHST strongly preferred the R-enantiomer. The r…
Expression of human estrogen sulfotransferase in Salmonella typhimurium: differences between hHST and hEST in the enantioselective activation of 1-hydroxyethylpyrene to a mutagen.
Various human sulfotransferases (hP-PST, hM-PST, hHST) and rat sulfotransferases (rPST-IV, rHSTa) have already been expressed in Ames' Salmonella strains (in particular in TA1538). Now a further strain, TA1538-hEST, which expresses the human estrogen sulfotransferase (hEST), has been constructed. This strain activated the primary benzylic alcohol 1-hydroxymethylpyrene (1-HMP) and the secondary benzylic alcohol 1-hydroxyethylpyrene (1-HEP) to mutagens. Human sulfotransferases hEST and hHST both activated 1-HEP, but they differed substantially in their enantioselectivity for this compound.