Folate and B12 Metabolism

Question 1

What is the most oxidized form of folate?

Answer 1

N10-formyl-THF

Question 2

What is the most reduced form of folate?

Answer 2

N5-methyl-THF

Question 3

What folate rxn is catalyzed by Serine Hydorxymethyltransferase?

Answer 3

THF to N5N10 methylene THF

Question 4

What is the most common form of folate found in the circulation?

Answer 4

N5-methyl-THF

Question 5

What enzymatic rxn keeps folate inside the cell?

Answer 5

addition of polyglutamate

Question 6

What form of folate is required for the production of serine from glycine? Produced?

Answer 6

THF

produced = N5N10-methylene THF

Question 7

What form of folate is required for methionine synthase?

Answer 7

N5-methyl-THF

produced = THF

Question 8

What form of folate is required for thymidylate synthase? Produced?

Answer 8

required = N5N10-methylene-THF

produced = dihydrofolate

Question 9

What form of folate is required for purine synthesis?

Answer 9

N10-formyl-THF

produced = THF

Question 10

What form of folate is required for histidine metabolism? Produced?

Answer 10

required = THF

produced = N5-formamino-THF

Question 11

What rxn does Thymidylate Synthase catalyze?

Answer 11

dUMP to dTMP

Question 12

What are the four forms of cobalamin?

Answer 12

cyanocobalamin

hydroxycobalamin

adenosylcobalamin

methylcobalamin

Question 13

What is B12 complexed to in order for reuptake into cells to function?

Answer 13

transcobalamin

Question 14

What type of cell produces transcobalamin?

Answer 14

ileal mucosa

Question 15

In what organelle is B12/TC degraded?

Answer 15

lysosome

Question 16

What protein is the majority of B12 complexed to in the circulation?

Answer 16

Haptocorrin

Question 17

Which form of cobalamin is B12?

Answer 17

cyanocobalamin

Question 18

What two forms of cobalamin must cyanocobalamin be converted into in order to function within the cell?

Answer 18

adenosylcobalamin

methylcobalamin

Question 19

How much of the radioactive form of B12 should a patient without a B12 deficiency urinate out during a negative Schilling Test?

Answer 19

at least 7%

Question 20

Will patients with an IF deficient have an abnormal Part 1 or Part 2 Schilling test?

Answer 20

Part 1

Question 21

What four amino acids get shunted into methylmalonyl-CoA?

Answer 21

Thr, Ill, Met, val

Question 22

What type of fatty acids get shunted through methylmalonic-CoA?

Answer 22

odd-chain

Question 23

Which cofactor is required for carboxylation of propionyl-CoA?

Answer 23

biotin

Question 24

Which form of cobalamin is required for converion of methylmalonyl-CoA to succinyl-CoA?

Answer 24

adenosylcobalamin

Question 25

Which form of cobalamin is required for the conversion of homocysteine to methionine?

Answer 25

methylcobalamin

Question 26

What rxn is the ONLY reaction that can regenerate THF from N5-methyl-THF?

Answer 26

methionine synthase

Question 27

What type of fatty acids will be accumulated into myelin during a B12 deficiency?

Answer 27

odd-chain

Question 28

What is the most common cause of acute megaloblastic anemia?

Answer 28

NO inhalation

Question 29

What form of cobalamin does nitrous oxide destroy?

Answer 29

methylcobalamin

Question 30

What two rxn’s are catalyzed by Dihydrofolate Reductase?

Answer 30

folate to dihydrofolate

dihydrofolate to tetrahydrofolate

Question 31

The folate receptor has the highest affinity for what form of folate?

Answer 31

N5-methyl-Folate

Question 32

What forms of folate are used during the activity of Methionine Synthase?

Answer 32

N5-Methyl to THF

Question 33

Folate receptors have the highest affinity for what form of folate?

Answer 33

monoglutamate

Question 34

Dietary folate contains what amino acid? How are these connected?

Answer 34

glutamate

polyglutamate

Question 35

What form of THF is found in the diet? Circulation?

Answer 35

diet = polyglutamate

circulation = monoglutamate

Question 36

In the portal blood, B12 is found complexed to what protein?

Answer 36

transcobalamin