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Chapter 4. Vitamins and
Coenzymes
Lecture 1. Water-soluble vitamins
and coenzymes
Lecture 2. Fat-soluble vitamins
Introduction of Vitamins
• Organic molecules, essential for the
normal growth and development,
required in tiny amounts
• Cannot be synthesized by mammalian
cells, must be supplied in the diet
The Classification of Vitamins

Water-soluble：thiamineVB1, riboflavinVB2,
pantothenic acid（VB3）, niacin（VPP、VB5）, VB6,
biotin（VB7）, folic acid（VB11 ?VB9 ）,
cobalaminVB12, VC

Fat-soluble：VA、VD、VE、VK
Lecture 1
Water-soluble Vitamins and Coenzymes
1. VitB3

Nicotinamide Coenzymes

Containing: nicotinic acid , nicotinamide
 Coenzyme：NADH and NADPH

Function：the coenzyme of dehydrogenase，
transfer of hydride anion
 The nicotinamide coenzymes play a role in
many oxidation–reduction reactions.
 Mechanism：
• Deficiency
• Pellagra.
呕吐、失眠、疲劳
Snapshot 7-8, p, 238
2. VitB2
Riboflavin—— precursor for the
coenzymes FAD, FMN
 Flavin Coenzymes

Riboflavin powder
FMN, FAD
Coenzyme：
Flavin mononucleotide
FMN
Flavin adenine dinucleotide
FAD
Function：electron acceptors and donors
in the oxidation-reduction reactions

FMN + 2H == FMNH2

FAD + 2H == FADH2
Deficiency：Growth retardation
3. VB5, Pantothenic Acid

Coenzyme A

“Pantothenic acid”

Function:
This coenzyme is involved in acylgroup–transfer reactions
 Deficiency:
4. VB1（ Thiamin）

Thiamin pyrophosphate（TPP）

The first discovery of vitamin

Structure：
Coenzyme: thiamine pyrophosphate
TPP
- cofactor for the pyruvate dehydrogenase
- α-ketoglutarate dehydrogenase
catalyzed reactions
- the coenzyme of pyruvate decarboxylase
- the transketolase catalyzed reactions of
the pentose phosphate pathway.

Deficiency：beriberi
sources：
Snapshot 7-6, p, 236
5. VitB6

Pyridoxine

Coenzyme：pyridoxal phosphate（PLP）and
pyridoxamine phosphate（PMP）
（—NH3)


Function：
Coenzymes of amino acid metabolism (transamination ,
decarboxylation, racemization)

Deficiency：
- Anemia
- Skin problems
- Sores in the mouth
Snapshot 7-11, p, 243
6. VitC

Ascorbic Acid
Reduction
Oxidation

Function：
•
Prevention of scurvy（protect the membrane）
•
Participate in oxidation-reduction reaction
•
The coenzyme of prolyl hydroxylase
（the synthesis of collagen protein ）

Deficiency：scurvy
Snapshot 7-5, p, 232
6. Biotin
 Vitamin

H （VB7）
Cocarboxylase
O
Urea
HN
Thiophene
C
NH
HC
CH
H2C
CH
S
(CH2)4
COOH
Pentanoate【戊酸】
Function：
Biotin is a
prosthetic group
for enzymes that
catalyze carboxyl
group transfer
reactions
and ATPdependent
carboxylation
reactions.
7. Folic Acid（ Folate）

VitM, VB11
6-Methylpteridin
p-Aminobenzoic acid (PABA)
Pteroic acid
Peteroylglutamic acid
Glutamic acid

Coenzymes：tetrahydrofolic acid（THFA, FH4）

Function：the coenzyme of one-carbon
units transferase

-CH3、-CH2-、-C(O)-H、=C-

Deficiency: megaloblastic anemia
8. VB12

Cobalamin

Function： Methyltransferases, Methyl (-CH3)
group transfers between two molecules.

Deficiency：pernicious anemia
Snapshot 7-10, p, 242
9. Lipoic Acid


Forms： lipoic acid （oxidized form）and
dihydrolipoic acid （reduced form ）
Function：electron carrier；acyl group carrier
Lecture 2
Fat-soluble Vitamins
1. VA

Retinol

Sources：animals and β-carotene
CH3
CH3
C
H
H
C
C
H
CH2OH
CH
CH3
CH3
CH3
C
H
C
H
C
H
CH3
H
C
CH2OH
CH
H3C CH3
H3C CH3
VA1
VA2
retinol
dehydroretinol
C
H

Deficiency: Night Blindness
Snapshot 7-1, p, 219
2. VD

Function：
Promotes calcium （Ca）and phosphonium（P）
absorption into intestine.
CH3
CH3
CH3
H CH3
C C C C C
H H2 H2 H2
CH3
Skin of animals：
7-dehydrocholesterol
CH3
CH3
HO
UV
CH2
230~300nm
HO
H CH3
C C C C C
H H2 H2 H2
CH3
VD3

Deficiency: rickets, osteomalacia
Snapshot 7-2, p, 223
3. VE
 -Tocopherol
 ，， and  are physiological active.
  -Tocopherol is the most active form.

Functions：
 Maintaining animal procreating ability,
anti-infertilitas.
 An antioxidant in cells： prevent the
oxidation of unsaturated fatty acids.
 Promote metabolism of heme.
Sources and Deficiency
Snapshot 7-3, p, 226
4. VK

They are 2-methyl-1,4-naphthoquinone (3-) derivatives
VK1
12
43
VK2

Functions：promote the blood clotting
• Blood coagulation: prothrombin (factor II), factors
VII, IX, and X, and proteins C, S, and Z
• Bone metabolism: osteocalcin, also called bone Gla
protein (BGP), matrix Gla protein (MGP),[36] and
periostin.
• Vascular biology: growth arrest-specific protein 6
(Gas6)

Deficiency: coagulopathy
Snapshot 7-4, p, 228