Folate Flashcards
Dietary sources
Beans, nuts, meat (esp. organs), dairy, fruit, grain, cereal
What amino acid does folate catabolize?
Histidine - transfers formimino group from formiminoglutamate to THF; results in formimino-THF and glutamate
What compound will be elevated in the urine during folate deficiency?
Formiminoglutamate
How does methotrexate work?
It is an anti-cancer drug that inhibits DHF reductase (traps DHF in cell), thus preventing THF formation that is needed to form thymidine. Cells can no longer divide quickly.
Role of folate in DNA synthesis
Needed to form thymidylate (pyrimidine) and purines (adenine and guanine)
Transmethylation role of folate
- Methylates homocysteine to methionine, which can then be used for various transmethylation reactions
- Methylaiton inactivates genes, which is important in development
B12 role in methylation
Required for MS to work to methylate homocysteine and maintain SAM
How does histone methylation work?
Methylation of chromatins turns off DNA, making DNA wrap tightly into histones. Removing methyl groups activates it, making it open. With insufficient SAM, genes will be turned on or off at the wrong time.
What lipid transmethylation reactions is folate involved in?
Sterol methylation
- making hormones
Phospholipid methylation
- formation of phosphatidylcholine (PC) requires methylation
- needed to get lipids out of the liver; or else fatty liver occurs because lipids accumulate
What does SAM methylate guanidinoacetate into?
Creatine
How much food folate is equivalent to folic acid and what is a DFE?
1mcg folic acid = 1.7mcg food folate
DFE = 1mcg food folate or 1.7 X 1mcg folic acid (folic acid is more bioavailable)
Requirements
M and F adults: 400mcg
Higher in pregnancy (600mcg DFE) and lactation (500mcg DFE)
UL of folate
1mg/day folic acid
- High doses can mask B12 deficiency
Food sources of folate
Plant and animal tissues - liver, dark green leafy veg, legumes
- Mostly found in polyglutamate form
- Mostly bound to proteins and storage polysacc
- Folic acid only found in fortified form
What is the bioavailability of food folate?
<50% depending on poly- or mono-glu form
- Organic acid inhibit conjugase activity
- Folate is trapped in plant material
- Lost during food processing