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Compare the structure, function and regulation of enzymes involved nitrogen fixation and nitrogen assimilation
Accepted Answer
Nitrogen fixation and nitrogen assimilation are crucial steps in the nitrogen cycle, each involving distinct enzymes with specialized structures and functions.
Nitrogen Fixation:
Enzyme: Nitrogenase
Structure: A complex metalloenzyme containing iron-sulfur clusters and molybdenum.
Function: Catalyzes the conversion of atmospheric nitrogen gas (N2) into ammonia (NH3), using electrons and protons.
Regulation: Highly regulated by oxygen levels, as nitrogenase is oxygen-sensitive. Also regulated by the availability of nitrogen and energy sources.
Nitrogen Assimilation:
Enzymes: Glutamine synthetase (GS) and glutamate synthase (GOGAT)
Structure: GS is a dodecameric enzyme with active sites for ammonia incorporation, while GOGAT is a tetrameric enzyme using NADPH as a reducing agent.
Function: GS incorporates ammonia into glutamate to form glutamine, which then serves as a nitrogen donor for various biosynthetic pathways. GOGAT uses glutamine and α-ketoglutarate to produce glutamate.
Regulation: GS activity is regulated by a feedback inhibition mechanism by glutamine. GOGAT activity is regulated by the availability of reduced coenzymes like NADPH.
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