Question

Question: What is the source of the methyl group in thymidine?

Short answer

The primary source of methyl group in thymidine is from N⁵, N¹⁰-methylene-THF. Tetrahydrofolate is a co-enzyme required by enzyme catalyzed reactions.

Step-by-step solution

The structure of N5, N10-methylene-THF

It is one of the co-enzyme of tetrahydrofolate transfers its methylene group to their substrates.

Source of methyl group in thymidine

Thymidine is derived by the addition of hydride ion from N⁵, N¹⁰-methylene-THF to uracil base. Thus,methyl group in thymidine is comes from the coenzyme N⁵, N¹⁰-methylene-THF. The methylene group of N⁵, N¹⁰-methylene-THF comes from the CH₂OH group of serine by means of a PLP catalyzed bond cleavage.

Thus, source of methylene group in thymidine base is explained.