Abstract
Polyamines (putrescine and spermidine) are present in almost all living organisms and participate in numerous cellular processes. In this study, we report the protective roles of polyamines against hydrogen peroxide (H 2O 2)-induced oxidative stress. All of ahpC, katG, and katE genes, known to participate in the antioxidant defense mechanism against H 2O 2-induced stress in Escherichia coli, failed to induce in the absence of polyamines during normal aerobic growth. The induction of both oxyR and rpoS gene expression, whose products are essential to induce ahpC, katG, and katE genes, was also absolutely dependent on polyamines. Polyamine-deficient E. coli mutant has increased susceptibility to exogenous H 2O 2, and this cell cytotoxicity was relieved to a wild-type level by addition of putrescine or spermidine (1 mM), which restored the transcriptional induction of ahpC, katG, and katE genes. H 2O 2-removing capacity was measured in the mutant, showing a significantly low H 2O 2-removing capacity compared to the wild type when polyamines were not present. We concluded that the increased susceptibility of the polyamine-deficient E. coli mutant to H 2O 2 treatment resulted from an intracellular low level of H 2O 2-removing capacity through the failure of their regulons, ahpC, katG, and katE induction, as well as the failure of oxyR and rpoS induction.
Published Version
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