B12 and Folate Flashcards
What nucleoside are both B9 and B12 used in the synthesis of?
Thymidine
Homocysteine levels are increased in what vitamin deficiencies?
B9 and B12
What enzyme converts dUridine-MP to Thymidine-MP?
Thymidylate Synthase
What is the difference between uracil and thymine?
Thymine has an extra carbon
Where does the carbon come from to make Thymidine-MP from dU-MP?
N5, N10 Tetrahydrofolate
What does N5, N10 Tetrahydrofolate become after the transfer of its carbon to make Thymidine-MP?
DHF
What enzyme converts DHF to THF?
Dihydrofolate reductase
What is Folate converted to and how is it then eventually converted to N5, N10 Tetrahydrofolate?
DHF (
tetrahydrofolate)
- THF
-> N5, N10 Tetrahydrofolate
What is the main function of N5, N10 Tetrahydrofolate?
Donates a Carbon to dUridine-MP to then become Thymidine-MP
What converts N5 Methyl THF into THF?
B12
What does S-Adenosyl Methionine (SAM) donate?
Methyl groups
What is S-Adenosyl Methionine (SAM) synthesised from?
ATP and methionine
SAM has a methyl group and Adenosine removed what does it become?
Homocysteine
B12 and Folate convert Homocysteine into what?
Methionine
Methionine + ATP yeilds what?
SAM
Methionine Synthase converts Homocysteine into what?
Methionine and Tetrahydrofolate
What are the causes of Megaloblastic anemia? (outside of B9 and B12 deficiency)
- Orotic aciduria
- Drugs (MTX, 5-FU, Hydroxyurea)
- Zidovudine (HIV, NRTIs)
What is the difference between Tetrahydrofolate and N5, N10 THF?
Addition of a carbon
- Used in thymidine synthesis
Why do alcoholics often have a folate deficiency?
- Decreased intake (nutrition)
- Poor absorption
What are the 3 drugs which interfere with folate deficiency?
- Phenytoin
- Trimethoprim
- Methotrexate
How does phenytoin cause folate deficiency?
Affects folate uptake
How can trimethoprim and Methtrexate cause folate deficiency?
Inhibiting Dihydrofolate reductase
DHF -> THF reaction
What element does cobalamin contain?
Cobalt
- Large, complex structure (corrin ring)
Where is B12 found?
Meats
- Only synthesised in bacteria