Question

Transamination is a process which involves
A. Reaction of ammonia with ketoglutaric acid and formation of glutamic acid
B. Transfer of amino group from one amino acid to a keto acid
C. Transfer of amino group from ketoglutaric acid to amino acid
D. Synthesis of amino acid

Answer 1

Amino acids are structural units of proteins. They are composed of amine () and carboxyl (COOH) functional groups, along with a side chain specific to each amino acid. Amino acids undergo a variety of reactions whereby the functional groups and the side chain are transferred or removed.

Complete answer:
Option (a) is incorrect. Reaction of ammonia with ketoglutaric acid results in the formation of glutamic acid. The reaction is a reductive amination reaction. The reaction can be summarized as follows:
$\alpha {\text{ - Ketoglutaric acid + NH}}_4^ + {\text{ + NADPH }}\xrightarrow{{{\text{Glutamate Dehydrogenase}}}}{\text{Glutamate + }}{{\text{H}}_{\text{2}}}{\text{O + NADP}}$
An enzyme called Glutamate Dehydrogenase accelerates the reaction. NAPH is a reducing co-enzyme that helps ammonia (${\text{NH}}_4^ +$) combine with ketoglutaric acid to form glutamate.
option (B). is correct. Transamination involves the transfer of an amino group from an amino acid to a keto acid. The reaction is reversible and forms Schiff base as an intermediate. Transamination results in the formation of a new keto acid and a new amino acid. For example, alanine reacts with $\alpha {\text{ - ketoglutarate}}$to form pyruvate and glutamate. Pyruvate is the new keto acid formed and Glutamate is the new amino acid formed. This reaction is catalyzed by Alanine aminotransferase. The reaction can be summarized as:
${\text{Alanine + }}\alpha {\text{ - Ketoglutarate }}\xrightarrow[{a\min otransferase}]{{Alanine}}{\text{ Pyruvate + Glutamate}}$
Option (c) is incorrect. Transfer of amino groups from $\alpha {\text{ - ketoglutaric acid}}$ is not possible since the compound does not have an amino group.
Option (d) is incorrect. Essential amino acids are obtained through the diet of an individual. Non-essential amino acids are synthesized in the body. The metabolic pathway that leads to amino acid synthesis comprises many steps. Primarily, most of the amino acids are synthesized from $\alpha {\text{ - ketoacids}}$. The $\alpha {\text{ - ketoacids}}$ are converted to Glutamate through animation. Glutamate is subsequently converted to different amino acids through transamination. Therefore, transamination forms a part of the amino acid synthesis pathways.
$\alpha {\text{ - keto acids + NH}}_4^ + {\text{ }} \rightleftarrows {\text{ Glutamate}}$
$\alpha {\text{ - keto acids + Glutamate }} \rightleftarrows {\text{ Amino acid + }}\alpha {\text{ - ketoglutarate}}$

Hence, the correct answer is option (B).

Note: Transamination is the process by which amino groups are transferred from an amino acid to a keto acid resulting in the formation of a new amino acid and a new ketoacid. The reaction is reversible and is regulated by an amino transferase or transaminase enzymes.