one carbon metabolism (16)

Question 1

what is the precursor for:
dopamine
epi
norepi

Answer 1

tryosine

Question 2

what is the precursor for:
melanin
thryoxine

Answer 2

all trosine

Question 3

what is the precursor for:
GABA
histidine

Answer 3

GABA- glutamate

histidine-histamine

Question 4

what is the rate limiting step in the formation of Dopa?

Answer 4

tyrosine hydroxylation

Question 5

what cofactor does tyrosine hydroxylase require?

Answer 5

tetrahydrobiopterin

Question 6

what enzyme degrades catecholamines?

Answer 6

monoamine oxidase (MAO)

Question 7

what enzyme does the conversion of dopamine to norepi?

Answer 7

dopamine b-hydroxylase

Question 8

what 2 things does the enzyme dopamine b- hydroxylase require?

Answer 8

ascorbate (vit C) and molecular oxygen

Question 9

what enzyme is need for norepi methylation to make epinephrine? what compound acts as the methyl donor?

Answer 9

enzyme: phenylethanolamine N methyltransferase

SAM is methyl donor

Question 10

what is disease is the result of a defect in the melanin producing pathway?

Answer 10

albinism

Question 11

what vitamin deficiency can result form a deficiency of tryptophan?

Answer 11

niacin deficiency- pellagra

Question 12

true or false

glutamate decarboxylase is a pyridoxal phosphate dependent enzyme

Answer 12

true

needed to make GABA

Question 13

what enzyme catalyzes the formation of histidine?

Answer 13

histidine decarboxylase

Question 14

what does histidine decarboxylase require?

Answer 14

pyridoxal phosphate

Question 15

list 4 reasons why the body needs single carbon fragments

Answer 15

o Formation of methionine form homocysteine
o Biosynthesis of purines
o Biosynthesis of pyrimidines
o Biosynthesis of glycine from CO2 and NH4+ by glycine synthase

Question 16

what carrier is able to carry the most oxidized one carbon group? what is “the most oxidized one carbon group”?

Answer 16

biotin carrying CO2

Question 17

when does THF act as a 1 carbon acceptor?

Answer 17

in degradative reactions

Question 18

when does THF act as a 1 carbon donor?

Answer 18

in biosynthetic reactions

Question 19

what precursor is the production of THF depend on?

Answer 19

dietary folate

Question 20

what part of THF are humans unable to synthesize?

Answer 20

the pterin ring

Question 21

what form of folate is normally seen in the diet?

Answer 21

polyglutamines with the glutamate moieties attached in y-peptidyl linkages

Question 22

is folate normally in the oxidized or reduced state before absorption?

Answer 22

oxidized state

Question 23

what enzyme is used to reduce folic acid to THF?

Answer 23

dihydrogolic acid reductase

Question 24

what is the name of the THF in the most reduced state?

Answer 24

N-5 methyl THF

Question 25

what is the name of the THF in the most oxidized state?

Answer 25

N-5 formyl THF N-5 formino THF N-5,N-10 methenyl THF

Question 26

what is the name of the THF in the intermediate state?

Answer 26

N-5,N-10 methylene THF

Question 27

what is the only reaction to use N5-methyl THF?

Answer 27

for the formation of methionine

Question 28

what reaction is the main source for making N5, N10-methlene THF

Answer 28

the interconversion of serine and glycine

Question 29

what are 3 drug classes that can cause folate deficiency?

Answer 29

1. oral contraceptives 2. barbiturates: impairs absorption & utilization 3. methotrexate: antimetabolite used in cancer chemo

Question 30

what are the two main drugs that are considered "anti folates"?

Answer 30

aminopterin | methotrexate

Question 31

list 5 important methylation reactions that require SAM

Answer 31

- Norepi→epi - Guanidinoacetate→creatine - Acetylserotonin→melatonin - Phosphatidylethanolamine to phosphatidylcholine - Methaylation of DNA

Question 32

what enzyme catalyzes the reaction of the regeneration of methionine from homocysteine?

Answer 32

homocysteine methyltransferase

Question 33

what 2 cofactors does homocysteine methyltransferase use?

Answer 33

N5 methyl THF | B12

Question 34

what disease process is elevated levels of homocysteine correlated with?

Answer 34

increased risk of athrosclerosis

Question 35

vitamin supplementation with what 3 compounds has been shown to reduce the levels of homocysteine?

Answer 35

B12 folate pyridoxal phosphate

Question 36

what enzyme catalyzes the reaction: homocysteine & serine condensing to form cystathionine? what is the cofactor for this enzyme?

Answer 36

cystathionine synthase | cofactor: pyridoxal phosphate

Question 37

what disease is caused by a deficiency in the enzyme cystathionine synthase?

Answer 37

homocystinuria

Question 38

people with homocystinurea have a higher risk of ____ and a lower risk of _____

Answer 38

higher risk of heart attacks | lower risk of colon cancer

Question 39

what version of cobalmin is seen in the MMAM reaction?

Answer 39

the adenosyl version

Question 40

what version of cobalamin is seen in teh HMT reaction?

Answer 40

hydroxyl version

Question 41

what two reactions in the body require cobalamin?

Answer 41

1. Conversion of L-methylmalonyl coA to succinyl coA | 2. the action of homocysteine methyltransferase

Question 42

what type of anemia does a deficiency in THF and B12 lead to?

Answer 42

megablastic anemia aka pernicious anemia

Question 43

what is a B12 deficiency associated with?

Answer 43

demyelination and degeneration of spinal cord

Question 44

what is usually the cause of a B12 deficiency?

Answer 44

a problem with intrinsic factor in the gut

Question 45

what is the name of the transporter for B12?

Answer 45

transcobalamine

Question 46

in the folate trap, what form is THF getting stuck in?

Answer 46

in the N5 methyl form (the most oxidized form)

Question 47

if a person is in a "folate trap" what does it manifest as?

Answer 47

anemia