page_title: Cytochrome c nitrite reductase
hierarchical_section_title: Cytochrome c nitrite reductase
caption_attribution_description: English: Crystallographic structure of the periplasmic cytochrome c nitrite reductase from Escherichia coli based on PDB coordinates 1GU6 (DOI:10.2210/pdb1gu6/pdb)
context_page_description: Cytochrome c nitrite reductase is a bacterial enzyme that catalyzes the six electron reduction of nitrite to ammonia; an important step in the biological nitrogen cycle. The enzyme catalyses the second step in the two step conversion of nitrate to ammonia, which allows certain bacteria to use nitrite as a terminal electron acceptor, rather than oxygen, during anaerobic conditions. During this process, ccNiR draws electrons from the quinol pool, which are ultimately provided by a dehydrogenase such as formate dehydrogenase or hydrogenase. These dehydrogenases are responsible for generating a proton motive force.
  Cytochrome c Nitrite Reductase is a homodimer which contains five c-type heme cofactors per monomer. Four of the heme centers are bis-histidine ligated and presumably serve to shuttle electrons to the active site. The active site heme, however, is uniquely ligated by a single lysine residue.
  This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with a cytochrome as acceptor. The systematic name of this enzyme class is ammonia:ferricytochrome-c oxidoreductase.
context_section_description: Cytochrome c nitrite reductase (ccNiR) (EC 1.7.2.2) is a bacterial enzyme that catalyzes the six electron reduction of nitrite to ammonia; an important step in the biological nitrogen cycle. The enzyme catalyses the second step in the two step conversion of nitrate to ammonia, which allows certain bacteria to use nitrite as a terminal electron acceptor, rather than oxygen, during anaerobic conditions. During this process, ccNiR draws electrons from the quinol pool, which are ultimately provided by a dehydrogenase such as formate dehydrogenase or hydrogenase. These dehydrogenases are responsible for generating a proton motive force.
  Cytochrome c Nitrite Reductase is a homodimer which contains five c-type heme cofactors per monomer. Four of the heme centers are bis-histidine ligated and presumably serve to shuttle electrons to the active site. The active site heme, however, is uniquely ligated by a single lysine residue.
  This enzyme belongs to the family of oxidoreductases, specifically those acting on other nitrogenous compounds as donors with a cytochrome as acceptor.  The systematic name of this enzyme class is ammonia:ferricytochrome-c oxidoreductase.
caption: Crystallographic structure of a homodimer of the cytochrome c nitrite reductase from Escherichia coli (rainbow colored cartoon, blue = N-terminus, red = C-terminus) complexed with heme C (sticks).[1]
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