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Oxidation of Sulfhydryl Compounds in Vitro by 4-Hydroxyaminoquinoline-1-oxide, a Carcinogenic Metabolite of 4-Nitroquinoline-1-oxide

Biochemistry Division, National Cancer Center Research Institute, Tsukiji, Chuo-ku, Tokyo, Japan, and Orchard Park Laboratories, Roswell Park Memorial Institute, Orchard Park, New York 14127

Glutathione and cysteine were found to be markedly oxidized by 4-hydroxyaminoquinoline-1-oxide in vitro at pH 7.0 at 37°C, but not at all by 4-aminoquinoline-1-oxide. The sulfhydryl compounds were oxidized by 4-hydroxyaminoquinoline-1-oxide to a much smaller extent in the absence of oxygen than in its presence. No substitution reaction between the sulfhydryl compounds and 4-hydroxyaminoquinoline-1-oxide was detected, nor any other alteration in the 4-hydroxyaminoquinoline-1-oxide. Regardless of the concentration of 4-hydroxyaminoquinoline-1-oxide used, oxidation followed first-order kinetics, indicating that the role played by the 4-hydroxyaminoquinoline-1-oxide is purely catalytic. Presumably, the reaction mechanism involves the formation of free radicals from 4-hydroxyaminoquinoline-1-oxide. The greater carcinogenic potency of 4-hydroxyaminoquinoline-1-oxide in comparison with 4-nitroquinoline-1-oxide may be correlated with the difference in the mode of reaction with sulfhydryl compounds.

¹ Visiting Scientist, Roswell Park Memorial Institute, on leave of absence from National Cancer Center Research Institute, Tokyo, Japan.

² Present address: Biochemistry Division, National Cancer Center Research Institute, Tsukiji, Chuo-ku, Tokyo, Japan.

Received 12/16/66. Accepted 4/ 5/67.