TitleHuman flavin-containing monooxygenase form 2 S-oxygenation: sulfenic acid formation from thioureas and oxidation of glutathione.
Publication TypeJournal Article
Year of Publication2004
AuthorsHenderson MC, Krueger SK, Stevens JF, Williams DE
JournalChem Res Toxicol
Date Published2004 May
KeywordsChromatography, High Pressure Liquid, Ethnic Groups, Ethylenethiourea, Flavins, Glutathione, Humans, Lung, Mass Spectrometry, Microsomes, Oxidation-Reduction, Oxygenases, Phenylthiourea, Sulfenic Acids, Thiourea, Xenobiotics

Thioureas are oxygenated by flavin-containing monooxygenases (FMOs), forming reactive sulfenic and/or sulfinic acids. Sulfenic acids can reversibly react with GSH and drive oxidative stress through a redox cycle. For this reason, thiourea S-oxygenation is an example of FMO-dependent bioactivation of a xenobiotic. Functional FMO2 is expressed in the lung of 26% of individuals of African descent and 5% of Hispanics but not in Caucasians or Asians. We have previously demonstrated that human FMO2.1 protein expressed in Sf9 microsomes has high activity toward a series of thioureas that are known or suspected lung toxicants including thiourea, 1-phenylthiourea, and ethylenethiourea. We now show by HPLC and LC-MS that 1-phenylthiourea and alpha-naphthylthiourea are converted to their sulfenic acids. GSH in the incubations at concentrations of 0.5-1.0 mM completely eliminated the sulfenic acid with resultant production of GSSG. These results indicate that individuals with the FMO21 allele may be at enhanced risk of pulmonary damage upon exposure to thioureas.

Alternate JournalChem. Res. Toxicol.
PubMed ID15144220
Grant ListR01 HL038650 / HL / NHLBI NIH HHS / United States
ES 00210 / ES / NIEHS NIH HHS / United States
HL38650 / HL / NHLBI NIH HHS / United States