One-Carbon Metabolism

Question 1

Which AAs provide one-carbon units to tetrahydrofolate?

Answer 1

serine and histidine

Question 2

Activated forms of THF are directly required for biosynthesis of ____, _____, and _____.

Answer 2

methionine, purines, and thymidylate

Question 3

homocysteine methyltransferase

Answer 3

catalyzes methionine synthesis

Question 4

what two cofactors does homocysteine methyltransferase require?

Answer 4

(1) folic acid

(2) vitamin B12

Question 5

How is S-adenosylmethionine synthesized?

Answer 5

transfer of adenosyl group from ATP to methionine

Question 6

SAM is a major donor of _______ for biosynthetic reactions

Answer 6

methyl gorups

Question 7

Defects in one-carbon metabolism may come from deficiencies in _____ and _______

Answer 7

folic acid and vitamin B12

Question 8

serine hydroxylmethyl transferase

Answer 8

major donor of one carbon units (does serene -> N5N10-methylene-THF);

Question 9

N5,N10 methylene-THF reductase

Answer 9

reduces N5,N10-methylene-THF to N5-methylene-THF; not reversible, dependent on NADPH

Question 10

homocysteine methyltransferase

Answer 10

• converts: homocysteine +N5-methyltetrahydrofolate –> methionine + THF
• req B12

Question 11

Name four molecules generated via SAM-dependent methylation

Answer 11

(1) choline
(2) creatine
(3) carnitine
(4) epinephrine

Question 12

folate trap

Answer 12

B12 deficiency –> buildup of N5Methyl THF - folate is “trapped” in this form –> depletes cells of needed THF