nitrogen fixation

Edge evidence

• nitrogenase enables nitrogen fixation RO:0002327

  The nitrogenase complex carries out biological nitrogen fixation.

  • DOI:10.1038/nrmicro954 Dixon & Kahn review nitrogenase as the catalyst of biological nitrogen fixation.
• nitrogen fixation consumes dinitrogen biolink:consumes

  Nitrogen fixation consumes atmospheric dinitrogen.

  • DOI:10.1038/nrmicro.2018.9 Kuypers et al. place N2 reduction as the reductive entry to the nitrogen cycle.
• nitrogen fixation produces ammonia METPO:2000202

  Nitrogen fixation produces ammonia.

  • DOI:10.1038/nrmicro954 Supports ammonia as the product of nitrogenase-catalyzed N2 reduction.
• nitrogen fixation depends on nitrogenase RO:0002502

  The nitrogen-fixation trait depends on the nitrogenase complex.

  • DOI:10.1038/nrmicro954 Supports nitrogenase as required for the trait.
• ferredoxin/flavodoxin transfers electron to NifH (Fe-protein)

  Reduced ferredoxin/flavodoxin donate electrons to the [4Fe-4S] cluster of the NifH homodimer.

  • DOI:10.1128/aem.00378-23 Reduced electron carriers donate electrons to the [4Fe-4S] cluster at the interface of the NifH homodimer; core Mo-nitrogenase mechanism.
• NifH (Fe-protein) transfers electron to P-cluster

  The Fe-protein accepts electrons from Fd/Fld and reduces the P-cluster in the MoFe protein in an ATP-dependent step.

  • DOI:10.1128/aem.00378-23 The Fe-protein FeS cluster accepts electrons from Fd or Fld and reduces the P-cluster in the MoFe protein in an ATP-dependent electron transfer.
• P-cluster transfers electron to FeMo-cofactor (M-cluster)

  The P-cluster relays electrons to the FeMo-cofactor for N2 reduction.

  • DOI:10.1128/aem.00378-23 The P-cluster delivers electrons to the MoFe cofactor allowing electrons to be loaded for the reduction of N2; core electron relay.
• FeMo-cofactor (M-cluster) enables nitrogen fixation RO:0002327

  The FeMo-cofactor binds and reduces N2 to ammonia.

  • DOI:10.34133/bdr.0005 FeMo-co binds and reduces N2 to form NH3 and H2 in the canonical Mo-dependent nitrogenase.
• NifH (Fe-protein) requires ATP

  NifH hydrolyzes Mg-ATP during each electron transfer to the MoFe protein.

  • DOI:10.34133/bdr.0005 NifH transiently binds and dissociates from NifDK, hydrolyzing 2 Mg-ATP per electron transfer; supports per-electron ATP cost.
• molecular oxygen inhibits nitrogenase RO:0002212

  Molecular oxygen inactivates the oxygen-sensitive nitrogenase complex.

  • DOI:10.1128/aem.00378-23 Nitrogenase is an O2-sensitive enzyme; broad, well-supported claim across diazotrophs.