Which enzyme is crucial for breaking down hydrogen peroxide in aerobic bacteria?
Aerobic respiration inevitably leaks electrons to dioxygen generating superoxide and hydrogen peroxide. H2O2 is particularly hazardous because ferrous iron drives Fenton reaction producing hydroxyl radical that nicks DNA phosphodiester backbone, carbonylates proteins, and peroxidizes lipids. Aerobes counter with catalase, extraordinarily efficient heme tetramer with kcat approaching ten million per second, diffusion limited perfect enzyme. Active site ferriprotoporphyrin IX cycles between ferric resting state and Compound I oxoferryl radical after binding first H2O2, then reduced by second H2O
Ref: Madigan et al., Brock Biology of Microorganisms, 16th ed., Chapter 6: Oxidative stress - Catalase mechanism.
