THF

[Oblique]

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Can someone explain to me why taking taking the methyl group off methyl-THF is required for Purine Synthesis?

I looked at FA's biochem section (2014, pg 67) but saw that methylene-THF is required for pyrimidine synthesis. Isn't methylene-THF a methylated form of THF? and how does THF play a role in purine synthesis; is it in one the reactions that FA shows as with a whole bunch of arrows --> --> --> ?

 

[Oblique]

I just did some more browsing and THF is one of those reactions. But can someone explain to me why the methyl-THF has to be demethylated (by vitB12) before it can participate in purine & pyrimidine synthesis?

 

[thehundredthone]

I'm not great with biochemistry, but de novo purine and pyrimidine synthesis utilises folate as N5-N10 methylene THF (CH2-THF) and not methyl THF (CH3-THF). Hence for the methyl THF to be utilised for purine and pyrimidine synthesis it must be converted to THF first before the methylene group is added.

Hopefully this image makes it clearer (Courtesy wikipedia, Author: PD Dr. med. habil. Stephan Gromer):

 

[Oblique]

Awesome. Thanks! just what I needed.