title: Bioactivation mechanism of the cytotoxic and nephrotoxic S-conjugate S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine.
abstract: The bioactivation of S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC) was studied with purified bovine kidney cysteine conjugate beta-lyase and with N-dodecylpyridoxal bromide in cetyltrimethylammonium bromide micelles as a pyridoxal model system. The beta-lyase and the pyridoxal model system converted CTFC to chlorofluoroacetic acid and inorganic fluoride, which were identified by 19F NMR spectrometry. 2-Chloro-1,1,2-trifluoroethanethiol and chlorofluorothionoacetyl fluoride were formed as metabolites of CTFC and were trapped with benzyl bromide and diethylamine, respectively, to yield benzyl 2-chloro-1,1,2-trifluoroethyl sulfide and N,N-diethyl chlorofluorothioacetamide, which were identified by gas chromatography/mass spectrometry. The bioactivation mechanism of CTFC therefore involves the initial formation of the unstable thiol 2-chloro-1,1,2-trifluoroethanethiol, which loses hydrogen fluoride to form the acylating agent chlorofluorothionoacetyl fluoride; hydrolysis of the thionoacyl fluoride affords the stable, terminal metabolites chlorofluoroacetic acid and inorganic fluoride. The intermediate acylating agent and chlorofluoroacetic acid may contribute to the cytotoxic effects of CTFC.
mesh_terms: D000818:Animals; D001711:Biotransformation; D013437:Carbon-Sulfur Lyases; D002417:Cattle; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000633:toxicity; D007668:Kidney / Q000201:enzymology* / Q000473:pathology; D008190:Lyases / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D008954:Models, Biological
chemical_list: C047601:S-(2-chloro-1,1,2-trifluoroethyl)cysteine; D008190:Lyases; D013437:Carbon-Sulfur Lyases; C019969:S-alkylcysteine lyase; D003545:Cysteine