Ferredoxin—nitrite reductase

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⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with an iron-sulfur protein as acceptor. The systematic name of this enzyme class is ammonia:ferredoxin oxidoreductase. This enzyme participates in nitrogen metabolism and nitrogen assimilation. It has 3 cofactors: iron, Siroheme, and Iron-sulfur.

This enzyme can use many different isoforms of ferredoxin. In photosynthesizing tissues, it uses ferredoxin that is reduced by PSI and in the root it uses a form of ferredoxin (FdIII) that has a less negetive midpoint potential and can be reduced easily by NADPH.^[1]

Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1ZJ8, 1ZJ9, and 2AKJ.

References

• Joy KW, Hageman RH (1966). "The purification and properties of nitrite reductase from higher plants, and its dependence on ferredoxin". Biochem. J. 100 (1): 263–73. PMC 1265119. PMID 4381617. 
• Ramirez JM, Del Campo FF, Paneque A, Losada M (1966). "Ferredoxin-nitrite reductase from spinach". Biochim. Biophys. Acta 118 (1): 58–71. doi:10.1016/s0926-6593(66)80144-3. PMID 5954064. 
• Zumft WG, Paneque A, Aparicio PJ, Losada M (1969). "Mechanism of nitrate reduction in Chlorella". Biochem. Biophys. Res. Commun. 36 (6): 980–6. doi:10.1016/0006-291X(69)90300-3. PMID 4390523.