The Escherichia coli btuE gene, encodes a glutathione peroxidase that is induced under oxidative stress conditions

► BtuE is the first bacterial glutathione peroxidase characterized biochemically. ► BtuE is the first glutathione peroxidase described in Escherichia coli. ► BtuE uses GSH, TrxA or TrxC as reducinf agents in vitro. ► btuE transcription is induced under oxidative stress conditions. Most aerobic organisms are exposed to oxidative stress. Looking for enzyme activities involved in the bacterial response to this kind of stress, we focused on the btuE-encoded Escherichia coli BtuE, an enzyme that shares homology with the glutathione peroxidase (GPX) family. This work deals with the purification and characterization of the btuE gene product. Purified BtuE decomposes in vitro hydrogen peroxide in a glutathione-dependent manner. BtuE also utilizes preferentially thioredoxin A to decompose hydrogen peroxide as well as cumene-, tert-butyl-, and linoleic acid hydroperoxides, confirming that its active site confers non-specific peroxidase activity. These data suggest that the enzyme may have one or more organic hydroperoxide as its physiological substrate. The btuE gene was induced when cells were exposed to oxidative stress elicitors that included potassium tellurite, menadione and hydrogen peroxide, among others, suggesting that BtuE could participate in the E. coli response to reactive oxygen species. To our knowledge, this is the first report describing a glutathione peroxidase in E. coli.