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Literature summary for 1.18.6.1 extracted from

  • Shaw, S.; Lukoyanov, D.; Danyal, K.; Dean, D.R.; Hoffman, B.M.; Seefeldt, L.C.
    Nitrite and hydroxylamine as nitrogenase substrates mechanistic implications for the pathway of N2 reduction (2014), J. Am. Chem. Soc., 136, 12776-12783 .
    View publication on PubMedView publication on EuropePMC
Search for more literature for 1.18.6.1

Inhibitors

Inhibitors Comment Organism Structure
H2 H2 competes with N2 binding and inhibits N2 reduction by the FeMo protein, but H2 does not inhibit NO2- reduction for the wild-type or either of the two MoFe protein variants Azotobacter vinelandii

Metals/Ions

Metals/Ions Comment Organism Structure
Fe2+
-
 Azotobacter vinelandii
Molybdenum
-
 Azotobacter vinelandii

Natural Substrates/ Products (Substrates)

Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
8 reduced ferredoxin + 8 H+ + N2 + 16 ATP + 16 H2O Azotobacter vinelandii overall reaction 8 oxidized ferredoxin + H2 + 2 NH3 + 16 ADP + 16 phosphate
-
 ?
hydrazine + reduced ferredoxin Azotobacter vinelandii
-
 2 NH3 + oxidized ferredoxin
-
 ?
hydroxylamine + reduced ferredoxin Azotobacter vinelandii
-
 NH3 + H2O + oxidized ferredoxin
-
 ?
additional information Azotobacter vinelandii nitrite and hydroxylamine are nitrogenase substrates. The proposed NO2- reduction intermediate hydroxylamine (NH2OH) is a nitrogenase substrate, reduction intermediates can be trapped, cf. EC 1.7.2.2 ?
-
 ?
N2 + 4 reduced ferredoxin Azotobacter vinelandii
-
 hydrazine + 4 oxidized ferredoxin
-
 ?
nitrite + 4 reduced ferredoxin + 5 H+ Azotobacter vinelandii
-
 hydroxylamine + H2O + 4 oxidized ferredoxin
-
 ?
nitrite + H+ + ATP + reduced ferredoxin Azotobacter vinelandii overall reaction NH3 + 2 H2O + 12 ADP + 12 phosphate + oxidized ferredoxin
-
 ?

Organism

Organism UniProt Comment Textmining
Azotobacter vinelandii P00459 several strains
-

Reaction

Reaction Comment Organism Reaction ID
4 reduced ferredoxin + 8 H+ + N2 + 16 ATP + 16 H2O = 4 oxidized ferredoxin + H2 + 2 NH3 + 16 ADP + 16 phosphate NO2- reduction by nitrogenase begins with the generation of NO2H bound to a state in which the active-site FeMo-cofactor (M) has accumulated two [e-/H+] (E2), stored as a (bridging) hydride and proton. Proton transfer to NO2H and H2O loss leaves M-[NO+], transfer of the E2 hydride to the [NO+] directly to form HNO bound to FeMo-cofactor is one of two alternative means for avoiding formation of a terminal M-[NO] thermodynamic sink. Mechanism for N2 reduction, detailed overview. NO2- reduction by nitrogenase begins with the generation of NO2H bound to E2, E2 has accumulated two [e-/H+], stored in the form of a hydride bridging between two Fe atoms and a proton bound to sulfur. Transfer of the E2 proton to the -OH of NO2H followed by loss of H2O formally leaves M-[NO+]. Nitrogenase is able to transfer the E2 hydride to [NO+], directly forming HNO bound to FeMo-cofactor at its resting-state redox level and totally avoiding formation of an M-[NO] sink Azotobacter vinelandii
a

Substrates and Products (Substrate)

Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
8 reduced ferredoxin + 8 H+ + N2 + 16 ATP + 16 H2O overall reaction Azotobacter vinelandii 8 oxidized ferredoxin + H2 + 2 NH3 + 16 ADP + 16 phosphate
-
 ?
hydrazine + reduced ferredoxin
-
 Azotobacter vinelandii 2 NH3 + oxidized ferredoxin
-
 ?
hydroxylamine + reduced ferredoxin
-
 Azotobacter vinelandii NH3 + H2O + oxidized ferredoxin
-
 ?
additional information nitrite and hydroxylamine are nitrogenase substrates. The proposed NO2- reduction intermediate hydroxylamine (NH2OH) is a nitrogenase substrate, reduction intermediates can be trapped, cf. EC 1.7.2.2 Azotobacter vinelandii ?
-
 ?
additional information nitrite and hydroxylamine as nitrogenase substrates. The proposed NO2- reduction intermediate hydroxylamine (NH2OH) is a nitrogenase substrate, reduction intermediates can be trapped, cf. EC 1.7.2.2 Azotobacter vinelandii ?
-
 ?
N2 + 4 reduced ferredoxin
-
 Azotobacter vinelandii hydrazine + 4 oxidized ferredoxin
-
 ?
nitrite + 4 reduced ferredoxin + 5 H+
-
 Azotobacter vinelandii hydroxylamine + H2O + 4 oxidized ferredoxin
-
 ?
nitrite + 7 H+ + 12 ATP overall reaction Azotobacter vinelandii NH3 + 2 H2O + 12 ADP + 12 phosphate
-
 ?
nitrite + H+ + ATP + reduced ferredoxin overall reaction Azotobacter vinelandii NH3 + 2 H2O + 12 ADP + 12 phosphate + oxidized ferredoxin
-
 ?

Cofactor

Cofactor Comment Organism Structure
ATP
-
 Azotobacter vinelandii
FeMo cofactor active site located, ability of the multimetallic catalytic FeMo cofactor cluster to accumulate multiple [e-/H+] Azotobacter vinelandii
Ferredoxin
-
 Azotobacter vinelandii

General Information

General Information Comment Organism
additional information comparison of reaction mecanisms of nitrogenase, EC 1.18.6.1, and multiheme cytochrome c nitrite reductase, ccNIR, EC 1.7.2.2, overview Azotobacter vinelandii
physiological function the enzyme is involved in the N2 fixation mechanism, that proceeds via two different pathways, overview. N2 and NO2- reduction pathways converge upon reduction of NH2NH2 and NH2OH bound states to form state H with [-NH2] bound to the FeMo cofactor. Final reduction converts reaction intermediates H to I, with NH3 bound to the FeMo cofactor, supporting a N2 fixation mechanism in which liberation of the first NH3 occurs upon delivery of five [e-/H+] to N2, but a total of seven [e-/H+] to FeMo cofactor when obligate H2 evolution is considered, and not earlier in the reduction process Azotobacter vinelandii