Amino Group Transfer—Recognizing a Transamination Reaction Which of the following equations correctly represents a transamination process mediated by an aminotransferase?

Introduction / Context:
Transamination reactions transfer an amino group from an amino acid to an α-keto acid, forming a new amino acid and a new α-keto acid. They are central to nitrogen metabolism, funneling amino groups toward glutamate and linking amino acid catabolism with the TCA cycle carbon skeletons.

Given Data / Assumptions:

• Aminotransferases require pyridoxal phosphate (PLP) as a cofactor.
• Common pairs include alanine/pyruvate and aspartate/oxaloacetate, with α-ketoglutarate/glutamate as the principal amino/keto pair.
• Reactions are reversible and do not release free ammonia.

Concept / Approach:
A hallmark example is aspartate aminotransferase: aspartate + α-ketoglutarate ⇄ oxaloacetate + glutamate. This swaps the amino group from aspartate to α-ketoglutarate, generating glutamate and the corresponding keto acid (oxaloacetate). Reactions that release NH3 are deamination, not transamination, and fatty acids do not participate in aminotransferase chemistry.

Step-by-Step Solution:

Verification / Alternative check:
Clinical assays of AST (aspartate aminotransferase) rely on this exact reaction, underscoring its physiological relevance.

Why Other Options Are Wrong:

• Options a/d: depict deamination with NH3 release, not transamination.
• Option b: includes a fatty acid (hexanoic acid), not a typical α-keto acid partner.
• Option e: alanine → acetyl-CoA is not a transamination and incorrectly releases NH3.

Common Pitfalls:
Confusing transamination (no free NH3) with oxidative deamination (generates NH3) and including non-keto acids like fatty acids as substrates.

Final Answer:
Aspartate + α-ketoglutarate ⇄ glutamate + oxaloacetate