Cofactors

Question 1

What are the redox cofactors?

Answer 1

NADH, NADPH, FAD/FMN, and Ascorbic Acid (Vitamin C)

Question 2

What is the vitamin precursor for NADH and NADPH?

Answer 2

niacin

Question 3

What are some sources of niacin in the diet?

Answer 3

meat, whole grains

Question 4

What deficiency is associated with a deficiency in niacin?

Answer 4

Pellagra – dermatitis, diarrhea, and dementia

Question 5

What type of reactions are NADPH involved in and what are some examples?

Answer 5

Detox and biosynthetic reactions

ex. cytochrome P450, HMG-CoA Reductase

Question 6

What is the vitamin precursor for FAD/FMN?

Answer 6

Riboflavin

Question 7

What dietary sources are there for riboflavin?

Answer 7

milk, eggs, organs, mushrooms

Question 8

What is characteristic in riboflavin deficiency?

Answer 8

Cheilosis, glossitis, normacytic anemia

Question 9

What types of reactions are FAD/FMN involved in and what are some examples?

Answer 9

Reaction: dietary oxidation

ex. CoQ, Succinate dehydrogenase

Question 10

What is the precursor for ascorbic acid?

Answer 10

Vitamin C

Question 11

What is the disease associated with deficient amounts of vitamin C?

Answer 11

Scurvy = slow wound healing, apathy, anemia

results in an inability to make collagen fibers due to lack of prolyl and lysyl hydroxylase

Question 12

Vitamin C is involved in what types of reactions?

Answer 12

Reactions: collagen synthesis, neurotransmitter synthesis (Dopamine –> norepinephrine), and O2 sensing

Question 13

What are the different activation-transfer cofactors?

Answer 13

Thiamine pyrophosphate (TPP), lipoate, CoA, biotin, cobalamin, and pyridoxal phosphatase (PLP)

Question 14

What is the vitamin precursor of thiamine pyrophosphate (TPP)?

Answer 14

Thiamine (vitamin B1)

Question 15

What are some diseases associated with vitamin B1 (TPP) deficiency?

Answer 15

Beriberi = cardiac problems or neuropathy; Wernike encephalopathy, Karsokoff psychosis, megaloblastic anemia

Question 16

What type of reactions are TPPs involved in?

Answer 16

Decarboxylations

Ex. pyruvate dehydrogenase (E1 subunit)

Question 17

What is the precursor of lipoate?

Answer 17

nothing!! hopefully this didn’t trick you…

Question 18

What type of reactions is lipoate involved in and what are some examples?

Answer 18

Transfers from decarboxylase to active site

ex. pyruvate dehydrogenase (E2 subunit), transacylase of a-KG DH

Question 19

What is the precursor of CoA?

Answer 19

pantothenoic acid (vitamin B5)

Question 20

What type of reactions is CoA involved in and what are some examples?

Answer 20

Reactions: covalently bind acyl groups

Ex. Coenzyme A

Question 21

What is the precursor for biotin?

Answer 21

nada

Question 22

What are causes for biotin deficiency?

Answer 22

eating lots of raw eggs (avidin)

Question 23

What are characteristics of biotin deficiency?

Answer 23

scaly dermatitis, alopecia

Question 24

What type of reactions is biotin involved in and what are some examples?

Answer 24

Reactions: carboxylation, FA synthesis, gluconeogenesis (prosthetic groups)
Ex. Acetyl CoA Carboxylase (ACC), pyruvate carboxylase

Question 25

What is the vitamin precursor for pyridoxial phosphate (PLP)?

Answer 25

vitamin B6

Question 26

What are some dietary sources of vitamin B6?

Answer 26

cereal, bananas, meat, rice

Question 27

What are some characteristics of vitamin B6 deficiency? What are some of these diseases?

Answer 27

seizures, diarrhea, anemia in infants, peripheral neuropathy in adults Disease: pyridoxine dependent epilepsy (PDE), antiquitin deficiency

Question 28

What types of reactions is PLP involved in and what are some examples?

Answer 28

Reactions: amino acid metabolism, produce niacin from Trp ex. transaminase --> ALT, AST

Question 29

What is the vitamin precursor for cobalamin?

Answer 29

vitamin B12

Question 30

What are some dietary sources of vitamin B12?

Answer 30

bacteria (milk, meat)

Question 31

What are deficiencies of vitamin B12 caused by and what are some characteristics of these diseases?

Answer 31

Causes: veganism, GI absorption problems Characteristics: megaloblastic anemia, weakness, FTT, seizures

Question 32

What type of reactions is vitamin B12 involved in and what is an example?

Answer 32

Reaction: transfer and rearrangement of methyl groups Ex. methionine synthase (folate pathway)

Question 33

Pernicious anemia is caused by a deficiency of what vitamin? And what is the pathophysiology behind this disease?

Answer 33

vitamin B12 Pathophys: B12 binds to R-binders in the stomach and travels to the intestine where the R-binders are destroyed by pancreatic proteases; B12 then binds with intrinsic factor (secreted from parietal cells in the stomach) and this complex is transported to GI tract to be absorbed in the ileum or returned to the liver by transcobalamins (TC). Since intrinsic factor is deficient, B12 is not able to circulate to the GI tract.