87619-82-7Relevant academic research and scientific papers
Assessing the health risks following environmental exposure to hexachlorobutadiene
Green, Trevor,Lee, Robert,Farrar, David,Hill, James
, p. 63 - 73 (2008/01/27)
Hexachloro-1,3-butadiene (HCBD) has been reported to be toxic to the rat kidney in a 2 year study at doses higher than 0.2 mg/kg/day. The toxicity is known to be a consequence of the metabolism of HCBD by glutathione conjugation and the renal β-lyase pathway. Neither toxicity data, nor data on the metabolism of HCBD, are available in humans. In the current work, the potential of HCBD to cause kidney damage in humans environmentally exposed to this chemical has been assessed quantitatively by comparing the key metabolic steps in rats and humans. To that end, the hepatic conjugation of HCBD with glutathione, the metabolism of the cysteine conjugate by renal β-lyases and N-acetyltransferases, and the metabolism of the N-acetylcysteine conjugate by renal acylases has been compared in vitro in rat and human tissues. Rates for each metabolic step were lower in humans than in rats; 5-fold for glutathione conjugation, 3-fold for β-lyase and 3.5-fold for N-acetyltransferase. Acylase activity could not be detected in human kidney cytosol. Use of these data in a physiologically based toxicokinetic model to quantify metabolism by the β-lyase pathway demonstrated that metabolism in humans was an order of magnitude lower than that in rats. At the no effect level for kidney toxicity in the rat the concentration of β-lyase metabolites was calculated by the model to be 137.7 mg/l. In humans the same concentration would be achieved following exposure to 1.41 ppm HCBD. This is in contrast to the figure of 0.6 ppb which is obtained when it is assumed that the risk is associated with the internal dose of HCBD itself rather than β-lyase metabolites.
Acylase-catalyzed deacetylation of haloalkene-derived mercapturates
Uttamsingh, Vinita,Anders
, p. 937 - 942 (2007/10/03)
Mercapturates (S-substituted N-acetyl-L-cysteines) are terminal metabolites formed by the glutathione-dependent metabolism of electrophilic xenobiotics, including haloalkenes. Acylases catalyze the hydrolysis of N- acyl-L-amino acids, including many xenobiotic-derived mercapturates, to give fatty acids and amino acids as products. Although several acylases have been identified, the acylases that catalyze the deacetylation of the haloalkene- derived mercapturates have not been identified and characterized. Acylase I catalyzes the deacetylation of some haloalkene-derived mercapturates, including S-(1,1,2,2-tetrafluoroethyl)-N-acetyl-L-cysteine, S-(2-chloro- 1,1,2-trifluoroethyl)-N-acetyl-L-cysteine, and S-(2-bromo-1,1,2- trifluoroethyl)-N-acetyl-L-cysteine [Uttamsingh, V., et al. (1998) Chem. Res. Toxicol. 11, 800-809]. In the studies presented here, we identified a rat kidney acylase that catalyzed the hydrolysis of the haloalkene-derived mercapturates S-(1,2-dichlorovinyl)-N-acetyl-L-cysteine, S-(1,2,3,4,4- pentachloro-1,3-butadienyl)-N-acetyl-L-cysteine, and S-(2,2-dibromo-1,1- difluoroethyl)-N-acetyl-L-cysteine. The substrate selectivity and amino acid sequence of the purified rat kidney acylase were studied. Although the sequence of the purified rat kidney acylase was somewhat identical with that of aspartoacylase, it did not catalyze the hydrolysis of N-acetyl-L- aspartate.
