Flashcards in Vitamin B12 and Folic Acid Deck (37):
What is another name for Vitamin B12?
What are sources for Vitamin B12?
(not present in plants)
What are the active forms of Vitamin B12?
How does SAM act upon substrates?
methylation of substrates
How is SAM formed?
Made from adenosine triphosphate (ATP) and methionine by methionine adenosyltransferase.
What are the two major disposal pathways for homoscysteine?
-Conversion to methionine (Req: Folate & B12) - remethylation
-Conversion to Cysteine (Req: B6/Pyridoxine) - transsulfuration
Deficiency of B12 results in the accumulation of Homocysteine and the...
trapping of THF in the methyl-THF form
The trapping of THF in the methyl-THF form due to B12 deficiency impairs synthesis of what?
DNA and RNA synthesis
trapped form of THF is known as
THF is short for?
Homocysteine + N5-Methyltetrahydrofolate undergo catalysis by which enzyme to form what?
Enzyme: Methionine synthase
Product: L-Methionine + THF
Oxidation of odd-chain fatty acids generate which three carbon fatty acid by-product?
Propionyl CoA carboxylase requires what?
What is another name for methionine synthase?
Pernicious anemia associated with homocystinuria specifically results from?
No intrinsic factor because of autoimmune destruction of parietal cells (therefore can't absorb B12)
Megaloblastic anemia must be treated with what?
BOTH folate and Vitamin B12
Is there a vitamin B12 deficiency in pernicious anemia?
No. It is caused by a lack of the ability to absorb B12.
Intrinsic factor, which carried B12 and helps for absorption into the muosa of the ileum, is produced by what cells?
Parietal cells of the Stomach
Folate and Vitamin B12 deficiency BOTH lead to:
- Homocysteinemia, increased risk for cardiovascular disease
THF is the active form of folic acid produced by which enzyme?
Homocystinuria occurs due to deficiency of which enzyme?
What are some other effects of homocysteine accumulation?
Lipid oxidation and platelet aggregation --> leads to fibrosis and calcification of atherosclerotic plaques
Cysteine metabolized by cysteine dioxygenase produces what? Which is important for what?
-Important for bile synthesis
Sulfate produced from cysteine catabolism is used as a precursor for what?
Formation of 3-Phosphoadenisine-5-Phosphate (PAPS; glycolipid ad GAG synthesis)
Folic acid is which B vitamin?
what are the active forms of Folic acid?
Tetrahydrofolate (THF) derivatives
What are the sources of Folic acid?
Green leafy vegetables
whole grain cereals
Folic acid is important in 1-C transfer reactions especially in what?
DNA and RNA synthesis (purines and thymidine), some amino acid metabolism (glycine serine, methionine from homocysteine, degradation of histidine)
Dihydrofolate reductase requires which cofactor in order to form THF?
Which vitamin deficiency has been implicated in spina bifida?
Folic Acid (B-9)
Serine to glycine interconversion is catalyzed by which enzyme? Requiring which cofactor?
FIGlu donates what group to what to produce what?
Donates: Formimino group
the degradation of Histidine requires what?
Histidine is eventually degraded to _______, which requires _____ to form _____.
Individuals who are deficient in folic acid show in increase in what in their urine?
Histidinemia is due to what deficiency?