In enzymology, a ferredoxin—nitrite reductase (EC 1.7.7.1) is an enzyme that catalyzes the chemical reaction NH3 + 2 H2O + 6 oxidized ferredoxin nitrite + 6 reduced ferredoxin + 7 H+ The 3 substrates of this enzyme are NH3, H2O, and oxidized ferredoxin, whereas its 3 products are nitrite, reduced ferredoxin, and H+.