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19 Cards in this Set

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  • Back
What does THF do?
It acts as a carrier of one-carbon units (e.g. formaldehyde, formate) in a variety of metabolic reactions.
List the forms of THF.
1. N10-formyl-THF
2. N5,N10-methylene -THF
3. N5-formimino-THF
4. Dihydrofolate
5. N5, methyl-THF
What is the only way to convert N5-methyl-THF to a more convenient form?
The methionine synthase reaction.
What is the methyl folate trap?
A vitamin B12 deficiency will lead to a build up of N5-methyl-THF, leading to a shortage of other forms of folate and subsequent impairment in processes in which they are involved.
What is N10-formyl-THF involved in?
Purine biosynthesis; contributes C2 and C8 of the purine ring.
What is N5,N10-methylene-THF involved in?
Thymidylate synthase; it methylates dUMP to yield thymidylate.
Of what are the sulfonamides analogs?
They are analogs of p-aminobenzoic acid (PABA)
What is the mechanism of the sulfonamides?
The drug inhibits dihydropteroate synthetase which is a bacterial enzyme that synthesizes folic acid, thus making these and other compounds that inhibit bacterial folate synthesis excellent antibiotics.
How are the fates of homocysteine, folate, and methionene linked?
They are linked in one-carbon metabolism, and with the help of vitamins B6 and B12 participate in a cycle that continually produces donors of one-carbon units for use in essential biochemical reactions.
How does a folic acid defiency manifest itself?
it is manifested as megaloblastic anemia, whih is the insufficient generation of mature red blood cells.
How is megaloblastic anemia treated?
it is treated with vitamin B12 and folate
a genetic defect in N5, N10-methylene-THF reductase can lead to ?.
What is the universal methyl donor?
What are the three main one-carbon donors?
THF, biotiin (CO2), and SAM (S-adenosylmethionine)
Levels of ? in the blood mirror the efficiency of ? and is now used as a useful diagnostic target for a variety of disorders associated with methylation.
Homocysteine, one-carbon metabolism
Defects in which enzyme cause homocysteinuria?
Homocystein's reactive thiol group could lead to ?.
Protein degradation
What is another route for homocysteine toxicity?
A descrease in the availability of (SAM)
What are the effects of decrease SAM levels?
it can cause hypomethylation and subsequent defects in gene expression, maintenance of DNA integrity and stability, mRNA processing, etc.