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Antimutagenic factors in bacterial cells and cultured broth
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71 Wakabayashi, K., M. Ochiai, M. Nagao and T. Sugimura, National Cancer Center Research Institute, Tokyo (Japan) Tyramine as a major precursor of mutagen which becomes mutagenic in soy sauce after nitrite treatment We previously reported that soy sauce, after nitrite treatment, showed marked direct-acting mutagenicity toward S. typhimurium TA100. Also, 2 j3-carboline derivatives were isolated from soy sauce as precursors of mutagens which become mutagenic after nitrite treatment (Wakabayashi et al. (1983) Proc. Natl. Acad. Sci. (U.S.A.), 80, 2912). Another precursor of mutagen has been isolated from soy sauce and identified to be tyramine. 1 mg of tyramine induced 27300 revertants of TA100 without $9 mix after nitrite treatment. This mutagenicity was due to one of the major products of tyramine and nitrite. The structure of this mutagen was determined to be 4-(2-aminoethyl)-6-diazo2,4-cyclohexadienone. The amount of tyramine in various kinds of soy sauce produced in Japan was from 17 to 2250 ~ g / m l .
72 Yamagata, H., T. K o d a m a and Y. Minoda, University of Tokyo, Tokyo (Japan) Antimutagenic factors in bacterial cells and cultured broth We screened antimutagenic factors in bacterial cells and cultured broth. Mutagens used were mitomycin C, sterigmatocystin, and tobacco tar neutral fraction. The bacteria were cultured in nutrient broth supplemented with glucose, and the culture filtrate and the cell extract were obtained. Each fraction was incubated with the mutagens and the activity of the mutagens after incubation was checked with the Rec assay method using spores of a repair-deficient strain of Bacillus subtilis. Among 62 bacterial strains tested, mitomycin
C, sterigmatocystin, and tobacco tar were inactivated by the culture filtrates of 12, 2, and 1 strains respectively and the cell extracts of 36, 6, and 4 strains respectively. From the effective strains, Pseudomonas convexa 4-87. which possessed strong antimutagenic activity toward mitomycin C in its cell extract, was chosen for further study. From the results of heat treatment, protease digestion, and dialysis, its antimutagenic factor appeared to be proteinous and to require cofactors such as N A D P H . Column chromatographically, it consisted of at least two fractions.
73 Yamaguchi, T., Joetsu University of Education, Joetsu, Niigata (Japan) Formation of mutagenic unsaturated aldehydes by reactions between saturated aldehydes and amino acids c~,/~-Unsaturated aldehydes showed high mutagenicities on Salmonella typhimurium TA100 without $9 mix, whereas saturated alkyl aldehydes did not. It was found that 2-butenal was formed in the reactions between acetaldehyde and various amino acids. In these reactions, amino acids acted as catalysts for the self-condensation of acetaldehyde. This condensation took place not only between two identical aldehyde molecules but also between unidentical aldehyde molecules, and the products formed were 2-alkenals, which were in general highly mutagenic. Analysis of commercial foods has shown that the following processed foods contain unsaturated aldehydes: many smoked foods, dried bonito, yoghurt, soy sauce, natto. sake, whisky, green tea and coffee. All of these foods were mutagenically positive on Salmonella tvphimurium TA100 without $9 mix. A relationship was found between the mutagenicities and the contents of unsaturated aldehydes in these foods. These findings suggest that unsaturated aldehydes constitute an important part of mutagenic components in foods.
71 Wakabayashi, K., M. Ochiai, M. Nagao and T. Sugimura, National Cancer Center Research Institute, Tokyo (Japan) Tyramine as a major precursor of mutagen which becomes mutagenic in soy sauce after nitrite treatment We previously reported that soy sauce, after nitrite treatment, showed marked direct-acting mutagenicity toward S. typhimurium TA100. Also, 2 j3-carboline derivatives were isolated from soy sauce as precursors of mutagens which become mutagenic after nitrite treatment (Wakabayashi et al. (1983) Proc. Natl. Acad. Sci. (U.S.A.), 80, 2912). Another precursor of mutagen has been isolated from soy sauce and identified to be tyramine. 1 mg of tyramine induced 27300 revertants of TA100 without $9 mix after nitrite treatment. This mutagenicity was due to one of the major products of tyramine and nitrite. The structure of this mutagen was determined to be 4-(2-aminoethyl)-6-diazo2,4-cyclohexadienone. The amount of tyramine in various kinds of soy sauce produced in Japan was from 17 to 2250 ~ g / m l .
72 Yamagata, H., T. K o d a m a and Y. Minoda, University of Tokyo, Tokyo (Japan) Antimutagenic factors in bacterial cells and cultured broth We screened antimutagenic factors in bacterial cells and cultured broth. Mutagens used were mitomycin C, sterigmatocystin, and tobacco tar neutral fraction. The bacteria were cultured in nutrient broth supplemented with glucose, and the culture filtrate and the cell extract were obtained. Each fraction was incubated with the mutagens and the activity of the mutagens after incubation was checked with the Rec assay method using spores of a repair-deficient strain of Bacillus subtilis. Among 62 bacterial strains tested, mitomycin
C, sterigmatocystin, and tobacco tar were inactivated by the culture filtrates of 12, 2, and 1 strains respectively and the cell extracts of 36, 6, and 4 strains respectively. From the effective strains, Pseudomonas convexa 4-87. which possessed strong antimutagenic activity toward mitomycin C in its cell extract, was chosen for further study. From the results of heat treatment, protease digestion, and dialysis, its antimutagenic factor appeared to be proteinous and to require cofactors such as N A D P H . Column chromatographically, it consisted of at least two fractions.
73 Yamaguchi, T., Joetsu University of Education, Joetsu, Niigata (Japan) Formation of mutagenic unsaturated aldehydes by reactions between saturated aldehydes and amino acids c~,/~-Unsaturated aldehydes showed high mutagenicities on Salmonella typhimurium TA100 without $9 mix, whereas saturated alkyl aldehydes did not. It was found that 2-butenal was formed in the reactions between acetaldehyde and various amino acids. In these reactions, amino acids acted as catalysts for the self-condensation of acetaldehyde. This condensation took place not only between two identical aldehyde molecules but also between unidentical aldehyde molecules, and the products formed were 2-alkenals, which were in general highly mutagenic. Analysis of commercial foods has shown that the following processed foods contain unsaturated aldehydes: many smoked foods, dried bonito, yoghurt, soy sauce, natto. sake, whisky, green tea and coffee. All of these foods were mutagenically positive on Salmonella tvphimurium TA100 without $9 mix. A relationship was found between the mutagenicities and the contents of unsaturated aldehydes in these foods. These findings suggest that unsaturated aldehydes constitute an important part of mutagenic components in foods.