sectionM Nitrogen metabolism.ppt

文档介绍：Section M Nitrogen metabolism
1. Reduction of N2 into ammonia (NH3 or NH4+)
2. Synthesis of the 20 amino acids.
3. Amino acid degradation
M1 Nitrogen fixation and assimilation
The nitrogen cycle
Nitrogen fixation
Nitrogen assimilation
The nitrogen in amino acids, purines, pyrimidines and other biomolecules es from atmospheric nitrogen.
Cyanobacteria (蓝藻细菌, photosynthetic) and rhizobia (根瘤菌, symbiont) can fix N2 into NH3.
The reduction of N2 to NH3 is thermodynamically favorable :
N2 + 6e- + 6H+ 2NH3 G`o = -
Certain bacteria can fix N2 into ammonia
N2 + 6e- + 6H+ 2NH3 G`o = -
The plex in certain bacteria catalyzes the conversion of N2 to NH3, which is the ultimate source of nitrogen for all the nitrogen-containing biomolecules.
The plex consists of
dinitrogenase and dinitrogenase redutase
ADP
ADP
4Fe-4S
4Fe-4S
(P-cluster)
Fe-Mo cofactor
e-
?
Fe-Mo cofactor
4Fe-4S
(P-cluster)
4Fe-4S
ADP
ADP
Molybdenum
N2 is believed to
be reduced at the
Fe-Mo cofactor
N2
Fe
Fe
Fe
Fe
Fe
Fe
Fe
S
S
S
S
S
S
S
S
S
Mo