A) amminase
B) nitrogenase
C) nitrate reductase
D) nitrite reductase
Correct Answer: B
Solution :
Rhizobium leguminosarum causes biological nitrogen fixation in root nodules of leguminous plants. A pigment leghaemoglobin is present in the root nodules, which is a oxygen scavanger, ie, protect the enzyme nitrogenase from\[{{O}_{2}}\]. Nitrogenase enzyme complex consists of two components, ie, the Fe-protein and Mo-Fe-protein. In the overall nitrogen reduction reaction \[{{N}_{2}}+8{{e}^{-}}+8{{H}^{+}}+16ATP\xrightarrow{{}}\] \[2N{{H}_{3}}+{{H}_{2}}+16ADP+16Pi\] Ferridoxin serves as an electron donor to the Fe protein, which in turn hydrolyzes ATP and reduces the MO-Fe protein. The Mo-Fe protein than can reduce numerous substrates some of which are as follows:| Reactions Catalyzed by Nitrogenase | |
| \[{{N}_{2}}\to N{{H}_{3}}\] | Molecular nitrogen fixation |
| \[{{N}_{2}}O\to {{N}_{2}}+{{H}_{2}}O\] | Nitrous oxide reduction |
| \[{{N}_{3}}\to {{N}_{2}}+N{{H}_{3}}\] | Azide reduction |
| \[{{C}_{2}}{{H}_{2}}\to {{C}_{2}}{{H}_{4}}\] | Acetylene reduction |
| \[2{{H}^{+}}\to {{H}_{2}}\] | Production |
| \[ATP\to ADP+{{P}_{1}}\] | ATP hydrolytic activity |
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