2. Electrons are transferred through a series- of carriers to 2 r its reduction on the nitrogenase complex Eight electrons are believed to be needed for each round of fixation reaction: with six for reducing one n2 and two for reducing 2 H** (to form H2) The electrons mainly come from reduced ferredoxin(from photophosphorylation) or reduced flavodoxin(from oxidative ph hosphorylation) and are transferred to dinitrogenase via dinitrogenase reductase
2. Electrons are transferred through a series of carriers to N2 for its reduction on the nitrogenase complex • Eight electrons are believed to be needed for each round of fixation reaction: with six for reducing one N2 and two for reducing 2 H+ (to form H2 ). • The electrons mainly come from reduced ferredoxin (from photophosphorylation) or reduced flavodoxin (from oxidative phosphorylation) and are transferred to dinitrogenase via dinitrogenase reductase
For each electron to be transferred from dinitrogenase reductase to dinitrogenase two ATPs are hydrolyzed causing a conformational change which reduces the electron affinity for the reductase (i.e., an increased reducing power) The oxidized and reduced dinitrogenase reductase dissociates from and associates with the dinitrogenase, respectively The nitrogenase is in imperfect enzyme: H, is formed along with NH
• For each electron to be transferred from dinitrogenase reductase to dinitrogenase, two ATPs are hydrolyzed causing a conformational change which reduces the electron affinity for the reductase (i.e., an increased reducing power). • The oxidized and reduced dinitrogenase reductase dissociates from and associates with the dinitrogenase, respectively. • The nitrogenase is in imperfect enzyme: H2 is formed along with NH3
The overall reaction catalyzed is 8H+8e+16ATP+16H20→ 2NH2 + H,+16ADP+16P
• The overall reaction catalyzed is: • N2 + 8H+ +8e - + 16ATP + 16H2O → • 2NH3 + H2 + 16ADP + 16Pi
cOa+ 4CO2+ 4 pyruvate 4 acetyl-CoA Electrons are transferred to N bound in the 8 Ferredoxin or 8 flavodoxin 6 B naydasinor) active site of dinitrogenase (oxidized) (red via ferredoxin/flavodoxin land dinitrogenase reductase Dinitrogen 8 Dinitrogenase reductase reductase (reduced) (oxidized) 16 ATP 个 16ADP +16P; 8 Dinitrogenase 8 Dinitrogenase reductase(reduced reductase(oxidized) +16ATP + 16ATP Dinitrogenase Dinitrogenase 2H++2e 2H+2e 2H+2e (oxidized) H N≡N H-N=N一H 2N H 2NH扌H2 N Diimine Hydrazine
Electrons are transferred to N2 bound in the active site of dinitrogenase via ferredoxin/flavodoxin and dinitrogenase reductase
Mo is believed to bind to the cavity of the Fe-Mo cofactor of the 3Fe-3s dinitrogenase active site. F 于e Fe 3Fe-3S e
N2 is believed to bind to the cavity of the Fe-Mo cofactor of the dinitrogenase active site. 3Fe-3S 3Fe-3S