The nitrogenase of diazotrophs
1
contains Cu-S center and uses 12 NADH to reduce one N₂
2
contains one (4Fe-4S) cluster and uses 8 FADH₂ to reduce one N₂
3
is a complex of Fe-protein and MoFe-protein and uses 16 ATPs to reduce one N₂
4
is a MoFe protein and uses 4 ATP and 4 FMNH₂ to reduce one N₂