Question

Which one of the following vitamins is associated with transfer of single carbon unit?

• A. Thiamin
• B. Niacin
• C. Pyridoxine
• D. Folacin

Hint:

Coenzyme Transfer Functions:
Folacin (THF) $\rightarrow$ One-Carbon units.
Thiamin (TPP) $\rightarrow$ Aldehydes $\alpha$-Keto decarboxylation.
Pyridoxine (PLP) $\rightarrow$ Amino groups (Transamination).
Niacin (NAD) $\rightarrow$ Hydride ions ($H^-$ Redox).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
One-carbon metabolism: tetrahydrofolate (THF) acts as the universal coenzyme carrier of activated one-carbon functional groups at various oxidation states.
Key Formula or Approach:
\[ \text{Folacin} \xrightarrow{\text{DHFR}} \text{Tetrahydrofolate (THF)} \xrightarrow{\text{Carries One-Carbon Moieties}} -\text{CH}_3, =\text{CH}_2, -\text{CHO}, -\text{CH}=\text{NH}, -\text{CH}= \]

Step 2: Detailed Explanation:
In coenzyme biochemistry and one-carbon metabolism:
- Folacin (Folic Acid Folate) is reduced intracellularly by dihydrofolate reductase to its active coenzyme form, Tetrahydrofolate (THF $\text{FH}_4$).
- THF serves as the primary biochemical carrier for transferring Single-Carbon (One-Carbon) Units (such as methyl [$- ext{CH}_3$], methylene [$= ext{CH}_2$], methenyl [$- ext{CH}=$], formyl [$- ext{CHO}$], and formimino [$- ext{CH}= ext{NH}$] groups) in the de novo biosynthesis of purines, thymidylate (dTMP), and methionine.

Step 3: Final Answer:
Hence, Folacin is associated with the transfer of single carbon units, corresponding to option (D).