During periods of excess protein intake or when glucose is scarce, the body catabolizes amino acids for energy. The first major step for most amino acids involves the removal of their α-amino group and its transfer to an α-keto acid, typically α-ketoglutarate. This enzymatic reaction is known as what, and what is the direct fate of the transferred amino group?
Show answer and explanation
The answer
Correct answer: A. Transamination, which transfers the amino group to α-ketoglutarate, forming glutamate.
Tested concept: Amino acid catabolism and transamination
Explanation
The initial step for the catabolism of most amino acids is transamination. In this reaction, the α-amino group from an amino acid is transferred to an α-keto acid, most commonly α-ketoglutarate. This transfer forms a new α-keto acid (from the original amino acid) and glutamate (from α-ketoglutarate). Glutamate then serves as a collector of amino groups, which can later be released as ammonia via oxidative deamination or used in other metabolic processes. Oxidative deamination, decarboxylation, and the urea cycle are distinct metabolic processes that occur later or serve different purposes in amino acid metabolism.
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