Bacterial type I nitroreductase (NTR) (NTR)

Bacterial type I nitroreductases (NTRs) are flavin-mononucleotide (FMN)-dependent enzymes that facilitate the oxygen-insensitive reduction of nitroaromatic compounds (UniProtKB P38489). These enzymes are primarily found in various bacterial species, such as Escherichia coli, and are notably absent from most eukaryotic cells, providing a basis for therapeutic selectivity (Roldan et al., 2008, FEMS Microbiol Rev). In clinical practice, NTRs are essential for the activation of several nitro-containing antibiotics, including metronidazole and nitrofurantoin, which are used to treat anaerobic infections (Williams et al., 2015, Microbiology). Beyond antimicrobial therapy, NTRs are a cornerstone of Gene-Directed Enzyme Prodrug Therapy (GDEPT), where the enzyme is expressed in cancer cells to convert non-toxic prodrugs like CB1954 into highly cytotoxic DNA-damaging agents (Green et al., 2013, Cancer Gene Ther). The enzyme's ability to perform obligatory two-electron reductions prevents the formation of superoxide radicals, distinguishing it from the oxygen-sensitive type II nitroreductases. Consequently, bacterial type I NTRs represent a versatile tool in both infectious disease management and targeted oncological interventions.

Other names

Oxygen-insensitive nitroreductaseMajor nitroreductaseNfsANfsBNAD(P)H-dependent nitroreductase

Bacterial type I nitroreductases catalyze the sequential two-electron reduction of nitro groups on prodrugs or antibiotics to form hydroxylamine or amine derivatives (Roldan et al., 2008, FEMS Microbiol Rev). In the case of prodrugs like CB1954, this reduction creates a potent DNA-crosslinking agent that induces apoptosis in the target cell (Green et al., 2013, Cancer Gene Ther). For antibiotics like metronidazole, the reduction generates reactive intermediates that disrupt bacterial DNA and proteins (Williams et al., 2015, Microbiology).