The nitrogenase complex is extremely labile to O, and various protective mechanisms have evolved Some diazotrophs exist only anaerobically Some cyanobacterial cells develop thick walls to prevent O2 from entering The bacteria in root nodules are isolated from O, by being bathed in a solution of the oxygen-binding protein leghemoglobin
3. The nitrogenase complex is extremely labile to O2 and various protective mechanisms have evolved • Some diazotrophs exist only anaerobically. • Some cyanobacterial cells develop thick walls to prevent O2 from entering. • The bacteria in root nodules are isolated from O2 by being bathed in a solution of the oxygen-binding protein leghemoglobin
花 Leghemoglobin produces it legume plants has ahigh affinity @2 and protects the (b) 2 um
Leghemoglobin, produced in legume plants, has a high affinity to O2 and protects the nitrogenase complex in rhizobia
4. Reduced nitrogen in the form of NHis assimilated into amino acids via a two-enzyme pathway First nhat is added to the side chain of glutamate to form glutamine in an ATP-dependent reaction catalyzed by glutamine Synthetase. Then the side chain amino group of GIn is further transferred to a-ketoglutarate to form Glu in a reaction catalyzed by glutamate synthase,an enzyme only present in bacteria and plants, not in animals
4. Reduced nitrogen in the form of NH4 + is assimilated into amino acids via a two-enzyme pathway • First NH4 + is added to the side chain of glutamate to form glutamine in an ATP-dependent reaction catalyzed by glutamine synthetase. • Then the side chain amino group of Gln is further transferred to a-ketoglutarate to form Glu in a reaction catalyzed by glutamate synthase, an enzyme only present in bacteria and plants, not in animals
The amide group of GIn is a source of nitrogen in the synthesis of a variety of compounds, such as carbamoyl phosphate Trp, His, glucosamine-6-P, CTP, and AMP The amino groups of most other amino acids are derived from glutamate via transamination
• The amide group of Gln is a source of nitrogen in the synthesis of a variety of compounds, such as carbamoyl phosphate, Trp, His, glucosamine-6-P, CTP, and AMP. • The amino groups of most other amino acids are derived from glutamate via transamination
CHCOo Newly fixed nitrogen HCNH coo -Glutamate in the form of NH4t is ATP + NH first incorporated into NH3 glutamate to form CH,-CO-P, Enzyme Glutamine ADP synthase glutamine HCNH,+ cOo Enzyme-bound r-glutamyl phosphate P+ADP+H+ CH2-CONH2 HCNH+ COo L-Glutamine
Newly fixed nitrogen in the form of NH4 + is first incorporated into glutamate to form glutamine