Vitamins/Coenzymes

Activation-Transfer Coenzymes

class of coenzymes that binds directly and transfers a portion of one substrate to another substrate
B1/TPP, B5/CoA, B7/Biotin, B6/Pyridoxal Phosphate, B9/Tetrahydrofolate, B12/Cobalamin

One-Carbon Carrier Cofactors

class of coenzymes that transfers one carbon to another substrate
B9/Tetrahydrofolate, B12/Cobalamin

Oxidation-Reduction Coenzymes

class of enzymes involved in oxidation-reduction reactions catalyzed by oxidoreductases

B1

Thiamine(B1) > Thiamine Pyrophosphate
reversible decarboxylation
alcoholism > deficiency > Beriberi (wet/dry), Wernicke-Korsakoff (dry)

B1/Thiamine Pyrophosphate Enzymes (4)

transketolase
alpha-ketoglutarate dehydrogenase
alpha-keto acid dehydrogenase
pyruvate dehydrogenase

B5

Pantothenate(B5) + cysteine + ATP > CoA/CoASH
CoA attachment
*phosphopantetheine group functions as coenzyme in acyl carrier protein > fatty acid synthase complex
deficiency rare > fatigue & depressionB

B5/Pantothenate Enzymes (2)

CoA ligase
CoA synthetase

B7

Biotin (B7)
carboxylation
binds to avidin in egg whites, inhibiting proper absorption > deficiency

B7/Biotin Enzymes (4)

pyruvate carboxylase
acetyl-CoA carboxylase
propionyl-CoA carboxylase
methylcronyl-CoA carboxylase

B6

Pyridoxine(B6) > Pyridoxal Phosphate (PLP)
transamination, decarboxylation
Dopamine/Serotonin synthesis
deficiency rare > microcytic anemia, peripheral neuropathy

B6/Pyridoxal Phosphate Enzymes (4)

aminotransferases (many)
aromatic L-amino acid decarboxylase (serotonin/dopamine synthesis)
alanine aminotransferase
DOPA decarboxylase

B9

Folate(B9) > Tetrahydrofolate
1C transfers to make purine rings
B12 involved in conversion of homocysteine to methionine
deficiency > neural tube defects in infants, megaloblastic anemia

B9/Tertrahydrofolate Enzymes (5)

serine hydroxymethyltransferase
thymidylate synthase (dTMP)
phosphoribosylglycinamide formyltransferase (purine)
formimidoyltransferase-cyclodeaminase (glutamate)
methionine synthase

B12

Cobalamin(B12)
1C transfer
gastric intrinsic factor bound to B12 for proper absorption in intestine
obtained from animal products in diet
deficiency > macrocytic anemia, mathylmalonic acidemia

B12/Cobalamin Enzymes (2)

methionine synthase
methylmalonyl CoA mutase

B3

Tryptophan > Niacin(B3) + ATP > NAD+
accepts hydride ion > NADH > ETC > ATP
mainly corn diet > deficiency > Pellagra

B3/NAD+ Enzymes

alpha-ketoglutarate dehydrogenase
isocitrate dehydrogenase
succinate dehydrogenase

B2

Riboflavin(B2) + ATP > FAD
prosthetic coenzyme > 2 electrons and 2 protons from succinate to FAD
deficiency > anemia with low RBC counts

B2/FAD Enzymes (4)

succinate dehydrogenase
acyl CoA dehydrogenase
branched-chain acyl CoA dehydrogenases
methylenetetrahydrofolate reductase

C

ascorbic acid
proline and lysine PTMs > collagen stabilization (Fe2+ > Fe3+ oxidation)
norepinephrine synthesis (Cu2+ > Cu+ reduction)
carnitine synthesis
cholesterol hydroxylation in bile acid synthesis
non enzymatic antioxidant

C Enzymes

prolyl hydroxylase
lysyl hydroxylase
dopamine hydroxylase

A

lipid soluble

dietary beta-carotenes (provitamin A) > beta-carotene-1 5, 1 5’-dioxygenase > 2 fretinal/retinoic acid (vit A) > stored in hepatic stellate cells > ligand for retinoic acid receptor (RAR), a nuclear hormone receptor > embryonic development
cofactor for photoreceptor rhodopsin in retina
deficiency (rare) > blindness, dry skin, infertility, infection

D

lipid soluble
diet (D2, D3) or synthesized by cholesterol derivative + UV light
ligand for VDR, a nuclear hormone receptor > transport of intestinal and renal calcium/mobilization of calcium from bone
deficiency > fatigue, muscle weakness, bone pain, depression

E

alpha-tocopherol
nonenzyme antioxidant (most widely distributed) against lipid peroxidation in cell membrane
deficiency > muscle weakness, vision deterioration, impaired immune function

K

blood coagulation
hepatic cells: K > microsomal quinone reductase > KH2 (cofactor for carboxylases > +carboxyl to glutamate in blood coagulation factor, prothrombin > proper cleavage on osteocalcin for binding calcium in bone metabolism
can be synthesized by gut bacteria
deficiency > lack of blood coagulation

What enzyme is targeted by Warfarin?

vitamin K epoxide reductase (recycles vitamin K epoxide > vitamin KH2/hydroquinone)