Nitrite reductase: Difference between revisions
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<StructureSection load='Cca.pdb' size='450' side='right' scene='Journal:JBIC:16/Cv/2' caption=''> | <StructureSection load='Cca.pdb' size='450' side='right' scene='Journal:JBIC:16/Cv/2' caption=''> | ||
'''Nitrite reductase''' (NIR) catalyzes the reduction of NO2 to NO. There are 2 classes of NIR: (1) A heme-containing cytochrome Cd type NIR. This enzyme contains 4 heme groups. Its d-type heme group binds NO<sub>2</sub>. (2) A copper-containing NIR which produces NO<sub>2</sub>. Under anaerobic conditions bacteria rely on the reduction of nitrogen oxide species to obtain energy. NIR is part of the nitrogen cycle used | '''Nitrite reductase''' (NIR) catalyzes the reduction of NO2 to NO. There are 2 classes of NIR: (1) A heme-containing cytochrome Cd type NIR. This enzyme contains 4 heme groups. Its d-type heme group binds NO<sub>2</sub>. (2) A copper-containing NIR which produces NO<sub>2</sub>. Under anaerobic conditions bacteria rely on the reduction of nitrogen oxide species to obtain energy. NIR is part of the nitrogen cycle used for this purpose. | ||
Cytochrome c nitrite reductase (ccNIR) is a central enzyme of the nitrogen cycle. It binds nitrite, and reduces it by transferring 6 electrons to form ammonia. This ammonia can then be utilized to synthesize nitrogen containing molecules such as amino acids or nucleic acids. However, ccNiR’s primary role is to help extract energy from the reduction; ammonia is simply a potentially useful byproduct. In general, heterotrophic organisms feed on electron-rich substances such as sugars or fatty acids. During the metabolism of these substances large numbers of electrons are produced. Many organisms use oxygen as the final acceptor of these electrons, in which case water is formed. However, some organisms can use alternative electron acceptors such as nitrite, which is where ccNiR comes in. | Cytochrome c nitrite reductase (ccNIR) is a central enzyme of the nitrogen cycle. It binds nitrite, and reduces it by transferring 6 electrons to form ammonia. This ammonia can then be utilized to synthesize nitrogen containing molecules such as amino acids or nucleic acids. However, ccNiR’s primary role is to help extract energy from the reduction; ammonia is simply a potentially useful byproduct. In general, heterotrophic organisms feed on electron-rich substances such as sugars or fatty acids. During the metabolism of these substances large numbers of electrons are produced. Many organisms use oxygen as the final acceptor of these electrons, in which case water is formed. However, some organisms can use alternative electron acceptors such as nitrite, which is where ccNiR comes in. | ||