Which coenzyme is essential for carrying out transamination reactions in amino acid metabolism?

INI-CET EXAM -2026

Biochemistry & Nutrition

Easy

Appeared in: INI-CET EXAM -2026

Explanation

Pyridoxal phosphate (PLP) is the active coenzyme form of Vitamin B6 (Pyridoxine).
It is essential for the function of aminotransferase enzymes, also known as transaminases.
These enzymes catalyze transamination reactions, which involve transferring an amino group from an amino acid to a keto-acid.
This process is a crucial step in the synthesis and degradation of amino acids.
During the reaction, PLP acts as a temporary carrier of the amino group, first accepting it from the amino acid and then donating it to the keto-acid.

Option A: Thiamine pyrophosphate (TPP) is the coenzyme for decarboxylation reactions, not transamination. It is primarily involved in carbohydrate metabolism.
Option B: Nicotinamide adenine dinucleotide (NAD) is an electron carrier involved in oxidation-reduction (redox) reactions. It accepts or donates electrons, but does not transfer amino groups.
Option D: Flavin adenine dinucleotide (FAD) is also an electron carrier for redox reactions, similar to NAD. Its role is to accept or donate electrons, not transfer amino groups.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Role of coenzymes in amino acid metabolism as background academic context rather than a clinical decision trigger.
Vitamin B6 (pyridoxine) deficiency can impair amino acid metabolism, leading to symptoms like peripheral neuropathy, dermatitis, and anemia, as PLP is also required for heme synthesis.
Certain drugs, like the anti-tuberculosis medication isoniazid, can induce B6 deficiency by forming a complex with pyridoxine, preventing its conversion to PLP. Patients on isoniazid are often given prophylactic B6 supplements.
What if? If a patient on isoniazid therapy develops tingling and numbness in their hands and feet (peripheral neuropathy), the nurse should suspect Vitamin B6 deficiency and anticipate an order for pyridoxine supplementation, as this drug interferes with PLP-dependent enzymes.

How to Approach the Question

First, identify the key process in the question stem: 'transamination reactions' in 'amino acid metabolism'.
Recall that transamination is the transfer of an amino group from one molecule to another.
Systematically review the primary function of each coenzyme listed in the options.
Thiamine pyrophosphate (TPP) is linked to carbohydrate metabolism and decarboxylation.
Nicotinamide adenine dinucleotide (NAD) and Flavin adenine dinucleotide (FAD) are primarily electron carriers in redox reactions.
Pyridoxal phosphate (PLP) is famously involved in a wide variety of amino acid transformations, including transamination.

Concept Tested & Keywords

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E6 One Stop Resource all for your Exam Needs in Biochemistry (pp 6-135 of 140) p. 80-82

E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart A (pp 1-239 of 478) p. 133-135