@article{open2984,
           month = {April},
           title = {Free spermidine evokes superoxide radicals that manifest toxicity},
          author = {Vineet  Kumar and Rajesh Kumar  Mishra  and Debarghya  Ghose and Arunima  Kalita and Pulkit  Dhiman  and Anand  Prakash and Nirja  Thakur  and Gopa  Mitra and Vinod D  Chaudhari  and Amit  Arora and Dipak  Dutta},
       publisher = {eLife},
            year = {2022},
            note = {The copyright of this article belongs to eLife },
         journal = {eLife},
        keywords = {E. coli; Escherichia coli; SpeG; biochemistry; chemical biology; chromosomes; gene expression; iron metabolism; oxidative stress; spermidine toxicity; superoxide radical.},
             url = {http://crdd.osdd.net/open/2984/},
        abstract = {Spermidine and other polyamines alleviate oxidative stress, yet excess spermidine seems toxic to Escherichia coli unless it is neutralized by SpeG, an enzyme for the spermidine N-acetyl transferase function. Thus, wild-type E. coli can tolerate applied exogenous spermidine stress, but {\ensuremath{\Delta}}speG strain of E. coli fails to do that. Here, using different reactive oxygen species (ROS) probes and performing electron paramagnetic resonance spectroscopy, we provide evidence that although spermidine mitigates oxidative stress by lowering overall ROS levels, excess of it simultaneously triggers the production of superoxide radicals, thereby causing toxicity in the {\ensuremath{\Delta}}speG strain. Furthermore, performing microarray experiment and other biochemical assays, we show that the spermidine-induced superoxide anions affected redox balance and iron homeostasis. Finally, we demonstrate that while RNA-bound spermidine inhibits iron oxidation, free spermidine interacts and oxidizes the iron to evoke superoxide radicals directly. Therefore, we propose that the spermidine-induced superoxide generation is one of the major causes of spermidine toxicity in E. coli.}
}