How are superoxide and hydrogen peroxide formed inside cells?
Mutant strains of E. coli that lack superoxide dismutase or catalases/peroxidases are very sick. Yet E. coli has no enzymes that produce O2- or H2O2 as deliberate products. So what is the source of the O2- and H2O2 that disable these mutants? We have found that some flavoenzymes inadvertently transfer electrons to dissolved oxygen when it bounces into their reduced cofactors. O2- is formed if one electron is transferred, and H2O2 is formed if two electrons are transferred. Not surprisingly, this behavior is particularly marked if the flavin is solvent-exposed, has a high electron density, and has a low reduction potential. Several respiratory dehydrogenases have these traits, and they generate significant O2- and H2O2 during respiration. However, genetic analyses show that the primary source(s) of oxidants inside E. coli lie outside the respiratory chain. The identification of these sources is currently an important goal of our lab. What biomolecules does superoxide damage? Superoxide
