The enhancing effect of cysteine and its derivatives on the mutagenic activities of the tryptophan-pyrolysis products, Trp-P-1 and Trp-P-2

Cysteine and its derivatives were found to enhance the mutagenic activity of the tryptophan-pyrolysis products, Trp-P-1 and Trp-P-2, as assayed by the Salmonella-microsome system. Several-fold increase in the number of revertant colonies was caused by addition of cysteine, cysteine ethyl ester and cysteamine at 10 mM concentrations to the reaction mixture containing the bacteria and the mutagen. Studies on the structural requirement for the enhancing effect suggest that both the thiol and the amino groups are necessary in order for the compound to exhibit the effect. The cysteine derivatives did not affect the mutagenic activity of either benzo[a]pyrene or the beef-extract mutagen.