ABSTRACT
Nitroreductases characterized as oxygen sensitive are enzymes which normally catalyze redox reactions involving substrates that are more relevant to primary metabolism. Very little is known about the structure or function of the bacterial nitroreductases. A majority of the nitroreductases isolated from mam-malian tissues were found to be quite sensitive to the presence of dissolved atmospheric oxygen. The cloning and overexpression of the Salmonella typhimurium nitroreductase should aid in the isolation and characterization of E. coli enzymes. The oxygen sensitivity of these enzymes was found to involve the molecular oxygen-mediated reoxidation of the one-electron reduced nitro anion radicai to the parent compound with the concomitant formation of superoxide. The reduced pyridine nucleotides, NADH or NADPH, are the most commonly used electron donors of the enzymes studied thus far. However, some enzymes are quite specific in their preference for either NADH or NADPH, while others which utilize these molecules exhibit no such preference.
