NfsA

NfsA is a flavin mononucleotide (FMN)-dependent nitroreductase enzyme encoded by the nfsA gene in Escherichia coli and related bacteria. It is one of the principal oxygen-insensitive nitroreductases in E. coli, the other being NfsB.

Biochemically, NfsA catalyzes the two-electron reduction of nitro groups in nitroaromatic compounds, using NADPH as the electron donor and FMN as a prosthetic group. This two-electron mechanism makes the enzyme less sensitive to oxygen than one-electron nitroreductases, enabling activity under aerobic conditions. The enzyme is typically soluble and cytoplasmic and can function as part of a nitroreductase system with NfsB.

Substrates for NfsA include various nitroaromatic compounds, such as nitrofurans used as antibiotics and environmental nitroaromatics. The enzyme contributes to the detoxification of nitroaromatics in bacteria and, under certain conditions, can participate in the activation of nitroaromatic prodrugs in research contexts.

Genetically, the nfsA gene is part of the nitroreductase family in E. coli and related bacteria. NfsA and NfsB share overlapping substrate ranges and can act in concert to reduce nitro groups, with each enzyme exhibiting distinct substrate preferences.

Significance: NfsA is a commonly studied model enzyme for nitroreduction, with relevance to antibiotic resistance research, bioremediation of nitroaromatic pollutants, and therapeutic strategies that exploit nitroreductase activity in enzyme-prodrug approaches.