Any feedback?
Please rate this page
(literature.php)
(0/150)

BRENDA support

Literature summary 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

Inhibitors

EC Number Inhibitors Comment Organism Structure
1.18.6.1 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

EC Number Metals/Ions Comment Organism Structure
1.7.2.2 Fe2+ initial and final states contain Fe(II) heme, catalytic heme in the Fe2+ state Azotobacter vinelandii
1.18.6.1 Fe2+
-
 Azotobacter vinelandii
1.18.6.1 Molybdenum
-
 Azotobacter vinelandii

Natural Substrates/ Products (Substrates)

EC Number Natural Substrates Organism Comment (Nat. Sub.) Natural Products Comment (Nat. Pro.) Rev. Reac.
1.7.2.2 hydroxylamine + ferrocytochrome c Azotobacter vinelandii cf. EC 1.7.99.1 NH3 + H2O + ferricytochrome c
-
 ?
1.7.2.2 nitrite + 4 ferrocytochrome c + 5 H+ Azotobacter vinelandii cf. EC 1.7.2.6 hydroxylamine + H2O + 4 ferricytochrome c
-
 ?
1.18.6.1 8 reduced ferredoxin + 8 H+ + N2 + 16 ATP + 16 H2O Azotobacter vinelandii overall reaction 8 oxidized ferredoxin + H2 + 2 NH3 + 16 ADP + 16 phosphate
-
 ?
1.18.6.1 hydrazine + reduced ferredoxin Azotobacter vinelandii
-
 2 NH3 + oxidized ferredoxin
-
 ?
1.18.6.1 hydroxylamine + reduced ferredoxin Azotobacter vinelandii
-
 NH3 + H2O + oxidized ferredoxin
-
 ?
1.18.6.1 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 ?
-
 ?
1.18.6.1 N2 + 4 reduced ferredoxin Azotobacter vinelandii
-
 hydrazine + 4 oxidized ferredoxin
-
 ?
1.18.6.1 nitrite + 4 reduced ferredoxin + 5 H+ Azotobacter vinelandii
-
 hydroxylamine + H2O + 4 oxidized ferredoxin
-
 ?
1.18.6.1 nitrite + H+ + ATP + reduced ferredoxin Azotobacter vinelandii overall reaction NH3 + 2 H2O + 12 ADP + 12 phosphate + oxidized ferredoxin
-
 ?

Organism

EC Number Organism UniProt Comment Textmining
1.7.2.2 Azotobacter vinelandii
-
 several strains
-
1.18.6.1 Azotobacter vinelandii P00459 several strains
-

Reaction

EC Number Reaction Comment Organism Reaction ID
1.7.2.2 NH3 + 2 H2O + 6 ferricytochrome c = nitrite + 6 ferrocytochrome c + 7 H+ reaction mechanism, overview. NO2- binds to the enzyme ccNIR catalytic heme in the Fe2+ state, accepts two protons, and releases H2O to form a moiety formally written as Fe(II)-[NO+]. The key mechanistic challenge in reducing NO2- is to avoid or overcome formation of the terminal Fe(II)-NO thermodynamic sink through one-electron reduction of Fe(II)-[NO+]. Enzyme ccNIR achieves this by two proton-coupled electron transfer reductions that promptly reduce Fe(II)-[NO+] to Fe(II)-[HNO]. The process involves recharging of the catalytic heme with electrons obtained through transfer from the other hemes of the enzyme and of the heme environment with protons Azotobacter vinelandii
a
1.18.6.1 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)

EC Number Substrates Comment Substrates Organism Products Comment (Products) Rev. Reac.
1.7.2.2 hydroxylamine + ferrocytochrome c cf. EC 1.7.99.1 Azotobacter vinelandii NH3 + H2O + ferricytochrome c
-
 ?
1.7.2.2 nitrite + 4 ferrocytochrome c + 5 H+ cf. EC 1.7.2.6 Azotobacter vinelandii hydroxylamine + H2O + 4 ferricytochrome c
-
 ?
1.18.6.1 8 reduced ferredoxin + 8 H+ + N2 + 16 ATP + 16 H2O overall reaction Azotobacter vinelandii 8 oxidized ferredoxin + H2 + 2 NH3 + 16 ADP + 16 phosphate
-
 ?
1.18.6.1 hydrazine + reduced ferredoxin
-
 Azotobacter vinelandii 2 NH3 + oxidized ferredoxin
-
 ?
1.18.6.1 hydroxylamine + reduced ferredoxin
-
 Azotobacter vinelandii NH3 + H2O + oxidized ferredoxin
-
 ?
1.18.6.1 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 ?
-
 ?
1.18.6.1 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 ?
-
 ?
1.18.6.1 N2 + 4 reduced ferredoxin
-
 Azotobacter vinelandii hydrazine + 4 oxidized ferredoxin
-
 ?
1.18.6.1 nitrite + 4 reduced ferredoxin + 5 H+
-
 Azotobacter vinelandii hydroxylamine + H2O + 4 oxidized ferredoxin
-
 ?
1.18.6.1 nitrite + 7 H+ + 12 ATP overall reaction Azotobacter vinelandii NH3 + 2 H2O + 12 ADP + 12 phosphate
-
 ?
1.18.6.1 nitrite + H+ + ATP + reduced ferredoxin overall reaction Azotobacter vinelandii NH3 + 2 H2O + 12 ADP + 12 phosphate + oxidized ferredoxin
-
 ?

Synonyms

EC Number Synonyms Comment Organism
1.7.2.2 ccNiR
-
 Azotobacter vinelandii
1.7.2.2 multiheme cytochrome c nitrite reductase
-
 Azotobacter vinelandii

Cofactor

EC Number Cofactor Comment Organism Structure
1.7.2.2 cytochrome c heme Azotobacter vinelandii
1.7.2.2 heme catalytic heme in the Fe2+ state Azotobacter vinelandii
1.18.6.1 ATP
-
 Azotobacter vinelandii
1.18.6.1 FeMo cofactor active site located, ability of the multimetallic catalytic FeMo cofactor cluster to accumulate multiple [e-/H+] Azotobacter vinelandii
1.18.6.1 Ferredoxin
-
 Azotobacter vinelandii

General Information

EC Number General Information Comment Organism
1.7.2.2 additional information comparison of reaction mechanisms of nitrogenase, EC 1.18.6.1, and multiheme cytochrome c nitrite reductase, ccNIR, EC 1.7.2.2, overview Azotobacter vinelandii
1.18.6.1 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
1.18.6.1 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