Cytochrome c nitrite reductase

Cytochrome c nitrite reductase
Identifiers
EC number 1.7.2.2
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

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.[1] 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.[2]

Cytochrome c Nitrite Reductase is a homodimer which contains five c-type heme cofactors per monomer.[3] 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.

Structural studies

The crystal structure for ccNiR from a number of difference species is available including, Escherichia coli 1GU6 , Wolinella succinogenes 1FS7, and Sulfurospirillum deleyianum 1QDB.

References

  1. ^ Clarke TA, Mills PC, Poock SR, Butt JN, Cheesman MR, Cole JA, Hinton JC, Hemmings AM, Kemp G, Söderberg CA, Spiro S, Van Wonderen J, Richardson DJ (2008). "Escherichia coli cytochrome c nitrite reductase NrfA". Meth. Enzymol. 437: 63–77. doi:10.1016/S0076-6879(07)37004-3. PMID 18433623. 
  2. ^ Simon J (August 2002). "Enzymology and bioenergetics of respiratory nitrite ammonification". FEMS Microbiol. Rev. 26 (3): 285–309. PMID 12165429. 
  3. ^ Einsle O, Messerschmidt A, Stach P, Bourenkov GP, Bartunik HD, Huber R, Kroneck PM (July 1999). "Structure of cytochrome c nitrite reductase". Nature 400 (6743): 476–80. doi:10.1038/22802. PMID 10440380. 

Further reading

  • R, Kroneck PM; Messerschmidt, A; Stach, P; Bourenkov, GP; Bartunik, HD; Huber, R; Kroneck, PM (1999). "Structure of cytochrome c nitrite reductase". Nature. 400 (6743): 476–80. doi:10.1038/22802. PMID 10440380. 
  • Bamford,V.A., Angove,H.C., Seward,H.E., Thomson,A.J., Cole,J.A., Butt,J.N., Hemmings, A. M., and Richardson, D. J. (2002). "Structure and spectroscopy of the periplasmic cytochrome c nitrite reductase from Escherichia coli". Biochemistry. 41: 2921–31. doi:10.1021/bi015765d.