Cytochrome c nitrite reductase
Class of enzymes
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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.[2] 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.[3]
| Cytochrome c nitrite reductase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
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] | |||||||||
| Identifiers | |||||||||
| EC no. | 1.7.2.2 | ||||||||
| Databases | |||||||||
| BRENDA | enzyme data | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | enzyme entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| Rhea | reactions | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| Gene Ontology | AmiGO / QuickGO | ||||||||
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Cytochrome c Nitrite Reductase is a homodimer which contains five c-type heme cofactors per monomer.[4] 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.
