Escherichia coli ferredoxin-NADP+ reductase and oxygen-insensitive nitroreductase are capable of functioning as ferric reductase and of driving the Fenton reaction.

Two free flavin-independent enzymes were purified by detecting the NAD(P)H oxidation in the presence of Fe(III)-EDTA and t-butyl hydroperoxide from E. coli. The enzyme that requires NADH or NADPH as an electron donor was a 28 kDa protein, and N-terminal sequencing revealed it to be oxygen-insensitive nitroreductase (NfnB).