The primary reactions that create amino acids are transamination and transamidation.
These reactions, coupled with the initial conversion of ammonia into glutamate and glutamine, play a crucial role in amino acid biosynthesis across various organisms. Let's break down these processes:
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Initial Ammonia Assimilation: All organisms utilize enzymes like glutamate dehydrogenase and glutamine synthetase to convert ammonia (a toxic compound) into glutamate and glutamine. These two amino acids serve as nitrogen donors.
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Transamination: This process involves the transfer of an amino group (-NH2) from an amino acid (like glutamate or glutamine) to a keto acid (a carbon skeleton). This results in the formation of a new amino acid and a new keto acid. The reaction is catalyzed by enzymes called transaminases or aminotransferases. For example, glutamate can donate its amino group to pyruvate to form alanine, with alpha-ketoglutarate being the other product.
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Transamidation: Similar to transamination, transamidation involves the transfer of an amide group (-CONH2) instead of an amino group. This is typically seen in the synthesis of asparagine from aspartate, using glutamine as the amide donor.
Essentially, these reactions allow cells to redistribute nitrogen among different carbon skeletons, ultimately creating the diverse array of amino acids required for protein synthesis and other metabolic processes.
