Step I Very basic biochem question.

[Old Style Nanny]

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Is there a role of glycine in conversion of THF to Methylene THF?

I've got this note where I have drawn glycine into the pathway in pyrimidine synthesis where Methylene THF is regenerated from DHF. But I don't remember drawing it!

Could I have confused glycine with methionine [SAM]? Does that have a role here?

 

[Phloston]

Is there a role of glycine in conversion of THF to Methylene THF?

I've got this note where I have drawn glycine into the pathway in pyrimidine synthesis where Methylene THF is regenerated from DHF. But I don't remember drawing it!

Could I have confused glycine with methionine [SAM]? Does that have a role here?

You've got homocysteine + H3C-THF + B12 --> DHF + methionine

But in order to get H3C-THF, you've gotta first get DHF back to THF via DHFR. Once at THF, you've got:

THF + serine --> H2O + H3C-THF + glycine.

Serine is also used (this is in FA) with homocysteine, via B6 and cystathione synthase --> cystathione.

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No idea why you called that a "very basic" question.

 

[Old Style Nanny]

You've got homocysteine + H3C-THF + B12 --> DHF + methionine

But in order to get H3C-THF, you've gotta first get DHF back to THF via DHFR. Once at THF, you've got:

THF + serine --> H2O + H3C-THF + glycine.

Serine is also used (this is in FA) with homocysteine, via B6 and cystathione synthase --> cystathione.

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No idea why you called that a "very basic" question.

I remembered everything you had mentioned except the part in bold! So without that connection, I was trying to reason through the homocysteine---CH3-THF--->methionine->SAM pathway in an attempt to figure out why I had drawn an amino acid (glycine) there.

And what was more confusing was the fact that I had drawn glycine as entering the CH3-THF regeneration pathway at THF ---> CH3-THF, rather than exiting like you have mentioned.

Thanks for clarifying! I think the bolded part is not in FA (I'm fairly certain as I did FA biochem only a week or so back).

 

[Phloston]

You remind me of myself when I had first started prepping for the USMLE. Eventually you'll realize how basic the USMLE really is and that 90% of the energy you put into learning is just for yourself.

(and I know this was for yourself 😉 )

 

[Old Style Nanny]

You remind me of myself when I had first started prepping for the USMLE. Eventually you'll realize how basic the USMLE really is and that 90% of the energy you put into learning is just for yourself.

(and I know this was for yourself 😉 )

Haha, I really hope it feels that way at the end! 🙂