Cofactors

Question 1

B6 name and reactions

Answer 1

PLP. Pyridoxal phosphate

All aminotransferases.
Glutamate Decarboxylase.
Deaminase
Racemase

L-DOPA to Dopamine

Glycogen phosphorylase

ALA synthetase (porphinobilinogen synthase, ALA dyhdratase)

Question 2

B9 name and reactions

Answer 2

Folate
generates THF compounds
Tetrahydrofolate when it is reduced by NADPH and Vitamin B3

Folic acid -> reduced to Dihydrofolate -> reduced to THF
.

Question 3

THF name and reactions

Answer 3

Tetrahydrofolate
Folic acid derivative.
One-carbon donor.

Methylene-THF, generated from formate, serine, or glycine

Methyl-THF. Generated by NADPH reduction of methylene-THF

Formyl-THF. Generated by oxidation of methylene-THF

THF deficiency causes megaloblastic anemia

Question 4

Vitamin B12

Answer 4

Cobalamin. Contains Cobalt. (and nitrogen)

1) Propionate -> Succinate
The terminal reaction for Odd-numbered Fatty Acids.

2) Homocysteine -> Methionine

Within Methionine Synthase: Accepts a methyl group from methyl-THF, and transfers it to homocysteine, generating Met.

Question 5

What is the only compound that can accept a methyl group from methyl-THF?

Answer 5

Cobalin, B12.

Question 6

What two cofactors are required to metabolize Propionyl-CoA

Answer 6

1) Biotin for the carboxylation reaction

2) Cobalamin (B12) for the isomerization of a methyl-malonyl-CoA

Question 7

TPP

Answer 7

Thiamine pyrophosphate, a B1 vitamin.

PDH complex, Pyruvate dehydrogenase enzyme

Pyruvate decarboxylase

Alpha-ketoglutarate Dehydrogenase

BCAA Dehydrogenase

Trasnketolase

Question 8

Usual cofactor for Carboxylation reactions

Answer 8

Biotin

Acetyl-Coa Carboxylase, FA synthesis

Propionyl-CoA carboxylase
Pyruvate Carboxylase
Methyl-Crotonyl-CoA carboxylase

Question 9

Usual cofactor for dehydrogenase reactions

Answer 9

TPP, (Thiamine pyrophosphate)

Is also involved in Pentose Phosphate Transketolase reactions.

Question 10

Three enzymes in which the identical E3 subunit is present

Answer 10

PDH complex (pyruvate -> acetyl-CoA

Alpha-Ketogluarate Dehydrogenase (TCA cycle)

Branched Chain Alpha Ketoacid Dehydrogenase

All contain TPP coenzyme

Question 11

Cofactors for Fatty Acid Synthase

Answer 11

Phosphopantetheine, Long flexible chain contains thiol and moves through the acyl-carrier protein portion.

Question 12

SAM reactions

Answer 12

S-adenosyl-methionine

Methyl donor, Generated from Methionine and ATP

Phenyelthanolamine N-Methyltransferase
Norepinephrine -> Epinephrine

also used by COMT
Catechol degradation.

Cytosine methylation

Question 13

BH4

Answer 13

Tetrahydrobiopterin,
Synthesized endogenously from GTP, but enzyme deficiencies of BH4 synthesis can affect these other enzymes needing BH4.

Needed by aromatic amino acid hydrolases

1) Phenylalanine hydroxylase (metabolism)
2) Tyrosine hydroxylase (Dopamine and Norepinephrine synthesis from DOPA)
3) Tryptophan 5-Hydroxylase (Serotonin Synthesis)

BH4 deficiency results in phenylketonuria due to inability to metabolize phenylalanine by phenylalanine hydroxylase.

Question 14

What substrate do Carboxylases usually use to obtain their carbon

Answer 14

Bicarbonate