Tetrahydrobiopterin

Tetrahydrobiopterin (BH4) is cofactor in the synthesis of the neurotransmitters dopamine, norepinephrine, epinephrine and melatonin. It is also a cofactor in the synthesis of nitric oxide.

MTHFR mutations
MTHFR A1298C is involved in converting 5-methylfolate (5MTHF) to tetrahydrofolate (THF), a reaction that produces one molecule of BH4. Mutations in this gene down regulate the methylation cycle and consequently, the production of BH4.