Nitrogen fixation Nitrogenase component

See also Component I, Metalloenzymes, Nitrogenase, Nitrogen Fixation, Figure 20.2, Ferredoxin, Nitrogen Fixation, Nitrogenase... 

The biological nitrogen fixation process is Introduced. Discussion focusses on the Dominant Hypothesis of nitrogenase composition and functioning. The enzyme system catalyzes the six-electron reduction of N2 to 2 NH3 concomitant with the evolution of H2. ATP hydrolysis drives the process. The two protein components of the enzyme,... 

Nitrogen Fixation in Nature The nitrogenase enzyme is a two-component protein that consists of an electron-transfer Fe protein and a catalytic protein [85]. Three different nitrogenase enzymes are known, which differ primarily in the nature of the putative active site within the catalytic protein. The most common form is the MoFe protein, in which the active site for nitrogen reduction, the so-called FeMo cofactor (FeMoco), is composed of seven irons, one molybdenum, and nine sulfides... 

Nitrogen fixation occurs only in certain prokaryotes and is catalyzed by the nitrogenases, which have two protein components. These are the Fe-protein, which acts as a specific reductant of the larger MoFe-... 

Biological nitrogen fixation is carried out by a highly conserved complex of proteins called the nitrogenase complex (Fig. 22-2), the crucial components of which are dinitrogenase reductase and dinitrogenase... 

Ferredoxin is used by nitrogenase reductase (component II), an enzyme of nitrogen fixation, and also by nitrite reductase, which catalyzes reduction of nitrite to ammonia... 

The enzyme system for nitrogen fixation consists of two separate proteins. Nitrogenase (also called component I or molybdenum-iron protein) catalyzes the reduction of N2. The other, nitrogenase reductase (also called component II or iron protein), transfers electrons from ferredoxin or flavodoxin to nitrogenase (Figure 20.4)... 

Place the follotving components, reactants, and products of the nitrogenase complex reaction in their correct sequence during the electron transfers of nitrogen fixation ... 

The conversion of dinitrogen to ammonia by nitrogenase enzyme in bacteria (sometimes in symbiosis with plants) is called nitrogen fixation. This process is essential to life, because it is the starting point of the synthesis of amino acids that are the components of proteins. Three kinds of nitrogenase enzymes are known, each of them containing two air-sensitive metalloproteins that can be easily separated ... 

The two components of the Fe-Mo protein nitrogenase, which is responsible for the fixation of nitrogen by microbes, have been purified and characterized from several sources. It seems that the enzyme acts through an elaborate mechanism which involves electron transport from one protein to the other promoted by reaction with Mg-ATP. Further results with a nitrogenase model have been reported. 

---