{'fraction_non_alphanumeric': 0.041721854304635764, 'fraction_numerical': 0.009271523178807948, 'mean_word_length': 5.656387665198238, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Mutagenicity of the mercapturic acid and other S-containing derivatives of hexachloro-1,3-butadiene.

The main metabolic pathway of the genotoxic environmental contaminant hexachloro-1,3-butadiene (HCBD) is the direct conjugation reaction with glutathione. To establish structure-effect relationships we studied the mutagenic activity of four S-containing HCBD conjugates with and without metabolic activating enzymes (S9 mix) in Salmonella typhimurium. The N-acetyl-S-pentachlorobutadienyl-L-cysteine (mercapturic acid) was clearly mutagenic after metabolic activation; its mutagenic activity was 48.6 revertants/micrograms or 18.7 revertants/nmol, which is, on a molar basis, a mutagenic response 80 times greater than that of the parent compound HCBD. The mutagenic effect of the mercapturic acid rather decreased by addition to the pre-incubation system of pyridoxal 5'-phosphate, a co-factor of the enzyme beta-lyase. Methyl-N-acetyl-S-pentachlorobutadienyl-D,L-homocysteinate, structurally closely related to mercapturic acid, exerted a weak mutagenic effect comparable to that of HCBD. The two S-containing HCBD metabolites (S-pentachlorobutadienyl-mercaptoacetic acid and pentachlorobutadienyl-methylthioether) did not reveal significant mutagenic effects. The results indicate the involvement of the enzyme N-deacetylase which catalyzes the conversion of mercapturic acid to the HCBD-cysteine conjugate. In addition a high substrate specificity of the C-S bond-cleaving enzyme beta-lyase was observed.