Iron protein supply

In this scheme the electrons are all supplied by the metal, which undergoes a change in oxidation state of six. In nitrogenase, electrons would be supplied from the iron protein and there would be no need for large changes in oxidation state in the molybdenum. 

A nitrogenase is a redox enzyme with multi-functions which comprised of MoFe-protein and Fe-protein. The molecular weight of MoFe-protein is about 2,20,000 and it contains two molybdenum atoms, 24-33 iron atoms and 24 27 sulfur atoms. The molecular weight of iron-protein is about 60,000 and it contains four irons and four sulfur atoms. They are very complicated. One possible mechanism of nitrogen fixation is that the MoFe-protein may bind in coordination with one end of dinitrogen molecule. The electron from Fe-S part in the cluster of Fe-protein and the proton from the solution may supply to dinitrogen molecule. 

The initial stages of iron incorporation requires the ferroxidase sites of the protein. Thereafter the inner surface of the protein shell provides a surface which supplies ligands that can partially coordinate iron but which leave some coordination spheres available for mineral phase anions, thereby enabling the biomineralization process to proceed, with formation of one or more polynuclear ferrihydrite crystallites. Iron is transferred from the ferroxidase sites to the core nucleation sites by the net reaction (Yang et ah, 1998) ... 

The situation prevailing in the crypt cell at the beginning of its differentiation into an enterocyte and before it has begun to climb towards the villus is shown in the lower panel. The cell s iron requirements are supplied by receptor-mediated diferric transferrin uptake from the basolateral membrane. The TfR in turn is involved in an interaction with the HFE protein, which decreases the affinity of TfR for diferric transferrin. The level of transferrin saturation, or some other factor, determines the amount of iron taken up, and presets the IRP system at a level that corresponds to the iron requirements of the organism. 

Two miCTonutrients of particular concern in vegan diets are vitamin B,2 and iron which are normally obtained from meat. A dietary supply of vitamin B,2 can be ensured from sources such as yeast extracts or soya protein. 

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