Question

Deficiency of Vitamin B6 (Pyridoxine) causes :
(A). Hampers serotonin production
(B). Epinephrine and Nor epinephrine are not produced properly
(C). GABA is not produced properly
(D). Protein is not produced properly
Choose the correct answer from the options given below:

• A. (A), (B) and (C) only.
• B. (A), (B) and (D) only.
• C. (B), (C) and (D) only.
• D. (A), (B), (C) and (D).

Hint:

Remember that Pyridoxal Phosphate (PLP) is the absolute king of amino acid decarboxylation.
Since all major biogenic amine neurotransmitters (GABA, Serotonin, Dopamine, Norepinephrine) require decarboxylation of their parent amino acids, Vitamin B6 deficiency quickly leads to severe neurological impairment.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Vitamin B6 (pyridoxine) is converted in the body into its active coenzyme form, pyridoxal 5'-phosphate (PLP).
PLP is an essential cofactor for over 100 enzymatic reactions, primarily those involving amino acid metabolism, including transaminations, deaminations, and decarboxylations.

Step 2: Detailed Explanation:
PLP is especially critical in the central nervous system as a coenzyme for decarboxylase enzymes that synthesize key neurotransmitters:
- (A) Serotonin: Synthesized from tryptophan via a two-step pathway. The second step (conversion of 5-hydroxytryptophan to serotonin) is catalyzed by aromatic L-amino acid decarboxylase, which is strictly PLP-dependent. (Correct)
- (B) Epinephrine and Norepinephrine: Synthesized from tyrosine. The decarboxylation of L-DOPA to dopamine (the precursor to norepinephrine and epinephrine) is catalyzed by DOPA decarboxylase, which is PLP-dependent. (Correct)
- (C) GABA ($\gamma$-aminobutyric acid): This major inhibitory neurotransmitter is synthesized from glutamate by glutamate decarboxylase, which is highly PLP-dependent. (Correct)
- (D) Protein production: While PLP is involved in amino acid metabolism, protein synthesis (translation on ribosomes) relies on mRNA, tRNAs, and ribosomes, and is not directly blocked or impaired in the manner of these neurotransmitter synthesis pathways.
Therefore, a deficiency in Vitamin B6 primarily compromises the enzymatic pathways producing serotonin, epinephrine/norepinephrine, and GABA, causing neurological symptoms (like seizures and depression).

Step 3: Final Answer:
The correct combination is (A), (B), and (C) only, corresponding to option (A).