Nitrogen fixation nitrogenase

NITRENE NITROGENASE NITROGEN FIXATION Nitroxide spin-labeled phospholipids, PHOSPHOLIPID FLIP-FLOP NOISE... 

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

O2 carriers), ferredoxins and cytochromes (redox processes), ferritin (iron storage), acid phosphatase (hydrolysis of phosphates), superoxide dismutases (O2 dismuta-tion) and nitrogenase (nitrogen fixation). A deficiency of iron in the body causes anaemia (see Box 21.6), while an excess causes haemochromatosis. 

Many key protein ET processes have become accessible to theoretical analysis recently because of high-resolution x-ray stmctural data. These proteins include the bacterial photosynthetic reaction centre [18], nitrogenase (responsible for nitrogen fixation), and cytochrome c oxidase (the tenninal ET protein in mammals) [19, 20]. Although much is understood about ET in these molecular machines, considerable debate persists about details of the molecular transfonnations. 

Non-enzvmatic simulation of nitrogenase reactions and the mechanism of biological nitrogen fixation. G. N. Schrauzer, Angew. Chem., Int. Ed. Engl., 1975, 14, 514-522 (36). 

The chemistry of nitrogen fixation and models of the reactions of nitrogenase. R. A. Henderson,... 

Fig. 12. The nitrogen fixation genes of Azotobacter vinelandii. This orgEinism has three nitrogenase systems, viz nif, vnf, and anf, which it uses for fixing N2 under different environmental conditions. The boxes with slanted hatching indicate the structural genes of the three systems, those colored dark gray are required for eiU three systems, and those with vertical hatching are required for both the vnf and anf systems.

In nature, nitrogen fixation is accomplished by nitrogenase, an enzyme that binds N2 and weakens its bonding sufficiently to break the triple bond. Only a few algae and bacteria contain nitrogenase. Our Chemishy and Life Box describes what is known about this enzyme. 

Iron-sulfur (Fe-S) proteins function as electron-transfer proteins in many living cells. They are involved in photosynthesis, cell respiration, as well as in nitrogen fixation. Most Fe-S proteins have single-iron (rubredoxins), or two-, three-, or four-iron (ferredoxins), or even seven/eight-iron (nitrogenases) centers. 

In Nature, nitrogen fixation is mediated by the enzyme nitrogenase according to Eq. (1) (6)... 

Iron, Fe2+ (d6) Iron, Fe2+ (d6) 4, tetrahedral 6, octahedral N-Thiolate O-Carboxylate, alkoxide, oxide, phenolate Electron transfer, nitrogen fixation in nitrogenases, electron transfer in oxidases... 

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