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http://forums.phoenixrising.me/index.php?threads/snps-interpretation-guide.32187/#post-497018
...And people with A1298C are inefficient at converting methylfolate back to folinic acid. It didn’t seem like that would be important, since they can convert it to methylfolate, and since they are taking the folinic, they will have plenty of that, too. In fact, that was my reasoning that led me to trial it. Here’s the rub: The problems associated with A1298C stem from a lack of BH4, which is used for a lot of things, but in particular it makes serotonin and dopamine. The important part is not how much you have, but which way the cycle turns.
BH4 and BH2 are the two forms of biopterin in the biopterin cycle. BH4 turns into BH2 when it makes serotonin and dopamine,
when it converts folinic acid to methylfolate, and other things that are important. To recycle it back to BH4 takes one of two enzymes. The first is MTHFR, in the reaction that converts methylfolate to folinic acid. If you’re taking folinic acid, the MTHFR enzyme is going to be converting it to methylfolate, not the other way round, not the way you want it to be turning. It’s trying to achieve equilibrium and you’re pushing the reaction one way, when to make BH4, it needs to go the other....