Functions as the terminal component of an NADH peroxidase (NADH:H(2)O(2) oxidoreductase) when using NADH:rubredoxin oxidoreductase (NROR) as the electron transport intermediary from NADH to Rbr2. H(+) + H2O2 + NADH = 2 H2O + NAD(+) Binds 3 Fe(3+) ions per subunit. Rubredoxin (Rd) increases the NADH consumption rate by serving as an intermediary electron-transfer shuttle between NROR and Rbr2. Various environmental stress conditions, e.g. oxidative stress (exposure to H(2)O(2)) and other stress factors such as salt, increased pH, high concentration of solvents or cold shock, do not lead to increased transcript levels of this gene. However, PubMed:15336429 shows that rbr2 is slightly up-regulated after exposure to air, but PubMed:19648241 shows it does not respond to the presence of O(2). Is not repressed by PerR.