One-Carbon Metabolism

Question 1

What is the reduced form of folic acid?

Answer 1

Tetrahydrofolate (THF)

Question 2

What converts folic acid to Tetrahydrofolic acid?

Answer 2

Dihydrofolate reductase

Question 3

What does Serine hydroxymethyltransferase do?

Answer 3

Converts Serine to Glycine! This pathway provides the major source of active one-carbon units in most cells.

Product is N5,N10-Methylene THF

Question 4

What does N5, N10-methylene-THF reductase do?

Answer 4

It converts N5, N10-Methylene-THF to N5-Methyl-THF.

THIS is NOT reversible

Question 5

What does Homocysteine Methyltransferase do?

Answer 5

It converts Homocysteine + N5-Methyl-THF –> Methionine and Tetrahydrofolate

Question 6

What happens if you do not have Vitamin B12?

Answer 6

Homocysteine Methyltransferase does not work well. Will have an accumulation of Homocysteine and N5-Methyl-THF

You will have depletion of N5,N10-Methylene-THF and the net effect is folate deficiency. Some symptoms include megaloblastic anemia

Question 7

What happens to methionine after it is formed?

Answer 7

It is converted to S-AdenosylMethionine (SAM)–> eventually SAM is converted to Homocysteine and the re-synthesis of methionine occurs