Sandbox Reserved 640: Difference between revisions

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The enzyme needed for nitrogen fixation is nitrogenase. However, this enzyme is inactivated by oxygen, but at the same time, oxygen is needed for the bacteria to reduce nitrogen to ammonia. This ambiguity is explained by the function of Leghemoglobin, which transports oxygen at a low but stable concentration allowing for the symbiotic operation of nitrogenase activity and bacterial respiration.  
The enzyme needed for nitrogen fixation is nitrogenase. However, this enzyme is inactivated by oxygen, but at the same time, oxygen is needed for the bacteria to reduce nitrogen to ammonia. This ambiguity is explained by the function of Leghemoglobin, which transports oxygen at a low but stable concentration allowing for the symbiotic operation of nitrogenase activity and bacterial respiration.  


==Implications and Applications==
Microorganisms that fix nitrogen are known as diazotrophs.  The main problem occurring for these organisms is the oxygen that interferes with nitrogenase, the enzyme that converts the nitrogen to ammonia.  The problem lies in the fact that some organisms need oxygen to live, but need it not interfere with nitrogenase.  Others fare better by living in low oxygen environments, so no help is necessary <ref name=ten>Postgate, J (1998). Nitrogen Fixation, 3rd Edition. Cambridge University Press, Cambridge UK.</ref>
The diazotrophs are split into two categories, one being free-living and the other symbiotic.  The free-living diazotrophs don’t need Leghemoglobin for nitrogen fixation as they have their own way of staying away from oxygen.  These evolutions could vary, including living in low-oxygen areas or respiring oxygen quickly enough to keep levels low. <ref name=ten /> <ref name=eleven>Smil, V (2000). Cycles of Life. Scientific American Library.</ref> 
Organisms that use Leghemoglobin form root nodules that are important symbiotically with different types of bacteria.  The legume family Fabecea consists of the species using Leghemoglobin, with some minor exceptions.  Examples of organisms in this family are clovers, soybeans, alfalfa, lupines, and peanuts <ref name=ten /> <ref name=eleven />. 
Other nitrogen fixing plants don’t need oxygen, or need very trace amounts, for nitrogen fixation.  Some need heterocysts, which are specific nitrogen-fixing cells, and have no need for Leghemoglobin because of its own anti-oxygen evolved state.  Examples of what could replace Leghemoglobins are proteins that are specific to scavenging oxygen out of the cells, as well as having multiple cell walls, one of which is a glycolipid, that helps to keep out oxygen <ref name=ten />. 


==Structure==
==Structure==
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<div style="text-align: center;"> NAD(P)H + H+ + 2 ferrileghemoglobin  NAD(P)+ + 2 ferroleghemoglobin </div>
<div style="text-align: center;"> NAD(P)H + H+ + 2 ferrileghemoglobin  NAD(P)+ + 2 ferroleghemoglobin </div>
Ferric Leghemoglobin can also be reduced to the ferrous form by free flavins in the presence of NADH or NADPH. Lastly, Leghemoglobin can be reduced to its ferrous form directly by physiological reductants. These reductants are various electron donors commonly found in plant cells, which reduce the Leghemoglobin nonenzymatically.<ref name=b/>.
Ferric Leghemoglobin can also be reduced to the ferrous form by free flavins in the presence of NADH or NADPH. Lastly, Leghemoglobin can be reduced to its ferrous form directly by physiological reductants. These reductants are various electron donors commonly found in plant cells, which reduce the Leghemoglobin nonenzymatically.<ref name=b/>.
==Implications and Applications==
Microorganisms that fix nitrogen are known as diazotrophs.  The main problem occurring for these organisms is the oxygen that interferes with nitrogenase, the enzyme that converts the nitrogen to ammonia.  The problem lies in the fact that some organisms need oxygen to live, but need it not interfere with nitrogenase.  Others fare better by living in low oxygen environments, so no help is necessary <ref name=ten>Postgate, J (1998). Nitrogen Fixation, 3rd Edition. Cambridge University Press, Cambridge UK.</ref>
The diazotrophs are split into two categories, one being free-living and the other symbiotic.  The free-living diazotrophs don’t need Leghemoglobin for nitrogen fixation as they have their own way of staying away from oxygen.  These evolutions could vary, including living in low-oxygen areas or respiring oxygen quickly enough to keep levels low. <ref name=ten /> <ref name=eleven>Smil, V (2000). Cycles of Life. Scientific American Library.</ref> 
Organisms that use Leghemoglobin form root nodules that are important symbiotically with different types of bacteria.  The legume family Fabecea consists of the species using Leghemoglobin, with some minor exceptions.  Examples of organisms in this family are clovers, soybeans, alfalfa, lupines, and peanuts <ref name=ten /> <ref name=eleven />. 
Other nitrogen fixing plants don’t need oxygen, or need very trace amounts, for nitrogen fixation.  Some need heterocysts, which are specific nitrogen-fixing cells, and have no need for Leghemoglobin because of its own anti-oxygen evolved state.  Examples of what could replace Leghemoglobins are proteins that are specific to scavenging oxygen out of the cells, as well as having multiple cell walls, one of which is a glycolipid, that helps to keep out oxygen <ref name=ten />. 


==Notes==
==Notes==
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