Nitrite reductases

Nitrite reductases are enzymes in plants and bacteria ; they play an important role in nitrogen assimilation by plants and nitrate respiration in bacteria ( denitrification ). Nitrite reductases catalyze the reduction of nitrite (NO ₂ ^- ) and belong to the oxidoreductases .

There are four classes of enzymes called nitrite reductase:

• the ferredoxin nitrite reductases ( EC  1.7.7.1 ) that only occur in plants and produce ammonium (NH ₄ ⁺ ):

  ${\displaystyle \mathrm {NO_{2}^{-}+6\ Ferredoxin_{red}+8\ H^{+}\rightarrow \ NH_{4}^{+}+6\ Ferredoxin_{ox}^{+}+2\ H_{2}O} }$

• the cytochrome cd ₁ ( EC  1.7.2.1 ) found in bacteria, which produces nitrogen monoxide (NO):

  ${\displaystyle \mathrm {\ NO_{2}^{-}+2\ H^{+}+Acceptor_{red}\rightarrow \ NO+\ H_{2}O+Acceptor_{ox}^{2+}} }$

• Cytochrome c ₅₅₂ in bacteria ( EC  1.7.2.2 ), which formally produces ammonia (NH ₃ ):

  ${\displaystyle \mathrm {\ NO_{2}^{-}+7\ H^{+}+6\ Acceptor_{red}\rightarrow \ NH_{3}+2\ H_{2}O+6\ Acceptor_{ox}^{+}} }$

• Nitrite reductase (NADPH) in bacteria and some fungi ( EC  1.7.1.4 ), which produces ammonium hydroxide (NH ₄ OH) when NADH or NADPH is consumed :

  ${\displaystyle \mathrm {\ NO_{2}^{-}+3\ NAD(P)H+4\ H^{+}\rightarrow \ NH_{4}OH+3\ NAD(P)^{+}+\ H_{2}O} }$

literature

• P. Atkins, T. Overton, J. Rourke, M. Weller, F. Armstrong: Biological Inorganic Chemistry. In: Shriver & Atkins Inorganic chemistry. Oxford University Press, Oxford [Oxfordshire] 2006, ISBN 0-19-926463-5 , 2006, pp. 754-755.
• PMH Kroneck, J. Beuerle, W. Schumacher: Metal-dependent conversion of inorganic nitrogen and sulfur compounds. In: A. Sigel, H. Sigel: Metal Ions in Biological Systems: Degradation of environmental pollutants by microorganisms and their metalloenzymes. M. Dekker, New York 1992, ISBN 0-8247-8639-4 , pp. 464-465.
• WJ Payne: Diversity in the Nitrogen Cycle. In: HL Golterman: Denitrification in the Nitrogen Cycle. Plenum Press, New York 1985, ISBN 0-306-42104-6 , p. 56.
• ET Adman: Structure and Functions of Small Blue Copper Proteins. In: PM Harrison: Metalloproteins. Part 1: Metal Proteins with Redox Roles. Verlag Chemie, Weinheim 1985, ISBN 3-527-26136-2 , p. 5.
• WZ Lee, WB Tolman: Toward synthetic analogues of linked redox and catalytic multimetal sites in proteins: a model of the histidine-cysteine ​​bridged dicopper array. In: Inorg Chem. 41 (22), Nov 2002, pp. 5656-5658. doi: 10.1021 / ic025937a . PMID 12401068 .
• S. Suzuki, K. Kataoka, K. Yamaguchi: Metal coordination and mechanism of multicopper nitrite reductase. In: Acc. Chem. Res. 33 (10), Oct 2000, pp. 728-735. doi: 10.1021 / ar9900257 . PMID 11041837 .
• M. Sundararajan, IH Hillier, NA Burton: Mechanism of nitrite reduction at T2Cu centers: electronic structure calculations of catalysis by copper nitrite reductase and by synthetic model compounds. In: J Phys Chem. B 111 (19), May 2007, pp. 5511-5517. doi: 10.1021 / jp066852o . PMID 17455972 .