5-methyltetrahydrofolic acid is not a methyl donor for biogenic amines: enzymatic formation of formaldehyde.
Contrary to previous reports, 5-methyltetrahydrofolic acid does not mediate the methylation of dopamine to epinine. Instead, this methyl donor is degraded enzymatically to formaldehyde, which condenses with dopamine to form a tetahydoisoquinoline derivative. The latter has chromotographic characteristics very similar to those of epinine, which likely accounts for the original misidentification of the product.
D000818:Animals; D001921:Brain / Q000201:enzymology; D002250:Carbon Radioisotopes; D002855:Chromatography, Thin Layer; D004298:Dopamine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism*; D005557:Formaldehyde / Q000378:metabolism; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000378:metabolism; D008697:Methane / Q000378:metabolism; D008744:Methylamines / Q000378:metabolism; D008745:Methylation; D051381:Rats; D012436:S-Adenosylmethionine / Q000378:metabolism; D013763:Tetrahydrofolates / Q000378:metabolism*
D002250:Carbon Radioisotopes; D007546:Isoquinolines; D008744:Methylamines; D013763:Tetrahydrofolates; D005557:Formaldehyde; D012436:S-Adenosylmethionine; D008697:Methane; D004298:Dopamine