Transcript Functions

维生素与辅酶
Vitamin And
Cofactors of Enzyme
contents
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introduction
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Water-soluble Vitamins
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Lipid-soluble Vitamins
1 Introduction
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Vitamins are essential nutrients that are required in
the diet, usually in trace amounts, because they
cannot be synthesized by the organism itself.
Necessary for maintenance of growth, health,
metabolic homeostasis.
Dietary deficiency cause diseases—— ‘-penia’ s
1.1 Discovery of vitamins：
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Sun Simiao(孙思邈) Tang dynasty,
Liver is applied to night-blindness( nyctalopia) Silverskin
for beriberi(脚气病）
1897 Dutch Dr. C. Eijkman Rice bran for beriberi
1906 GB F. G. Hopkins
Rats cannot survive on purified feed( including pr, fat,
sacharides, minerals)
Normal growth with trace milk
Nutritional co-factors—— Vitamin。
without common chemical structure (aliphatic, aromatic,
steroids and heterocyclic compound)
1.2 Classification of Vitamin
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Fat-soluble vitamins:
A, D, E, and K
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Water-soluble vitamins:
B complex vitamins, Folic acid
and ascorbic acid, also known as
vitamin C.
Fat-soluble vitamins
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Participate in modulation of certain
functions
Vitamin A
Antixerophthalmic ~ 抗干眼病~
Vitamin D
Antirachitic ~ 抗佝偻病~
Vitamin E
Antisterility ~ 抗不育
Vitamin K
Antihaemorrhagic ~抗出血~
Water-soluble Vitamins
Co-enzymes that participate in group transfer
Vitamin B1
Vitamin B2
Vitamin B6
Vitamin B12
Antineuritic ~ 抗神经炎~
Antistomatoglossic ~ 抗口舌炎~
Pyridoxal ~ 抗皮肤炎~
Anti-pernicious anaemia ~抗恶性贫
血~
Vitamin PP（ B5）
Anti-pellagra ~ 抗癞皮病 ~
Pantothenic acid(B3)Anti-keratic ~ 抗皮肤角膜炎~
Biotin （ B7）生物素 Anti-seborrhea ~ 抗皮脂溢出~
Folic acid 叶酸
Anti-anemia ~ 抗贫血~
Vitamin C
antiscorbutic ~ 抗坏血病~
2 Fat-soluble Vitamins
2.1 Vitamin A——retinols
VA2 dehydroretinol
VA1
Retinol →retinal →retinoic acid
retinol
2.2
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Vitamin D (anti- osteomalacia ~)
4 identified types: D2, D3, D4, D5
Most important of which are:
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D2(麦角钙化醇ergocalciferol)
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D3(胆钙化醇 cholecaciferol)
Functions:
To promotes Ca, P intake and osteogenesis
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Active type:
1，25-dihydnxycholecalciferol
R
VD2
VD3
VD4
VD5
vitamin D–binding protein
(DBP), also known as
transcalciferin
Active form
The functions of 1，25-dihydnxycholecalciferol
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Participate in modulation of
Ca-P balance (absorption,
mobilization, osteogenesis
and renal reuptake)
Elevate blood phosphorus
and calcium concentration
Promote osteogenesis/
calcification
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1，25-二羟胆钙化醇
2.3 Vitamin E ( tocopherol)
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Centchroman derivate
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Nature structure:
tocopherol & 生育三烯酚
Each type is divided, according to methyl
number and position, into 8 kinds,α, β, γ, δ, etc.
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α – tocopherol has the strongest activity
structure
母育酚（tocol）
α-生育酚（α-tocopherol，5,7,8-trimethyltocol）
β-生育酚（β-tocopherol，5,8-dimethyltocol）
γ-生育酚（γ-tocopherol，7,8-dimethyltocol）
δ-生育酚（δ-tocopherol，8-methyltocol）
ζ2-生育酚（ζ2-tocopherol，5,7-dimethyltocol）
η-生育酚（η- tocopherol，7-methyltocol）
ε-生育酚（ε-tocopherol）
ζ1-生育酚（ζ1-tocopherol）
Functions:
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(1) Antioxidation ，protect unsaturated fatty acids in
membranes . When human plasma levels are low, red
blood cells are increasingly subject to oxidative
hemolysis.
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(2) Maintain procreative function. Deficiency causes
ambloma.
Sourses:
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Plant oil
Beans
vegetables
2.4 Vitamin K
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Naphthoquinone with isoprene sidechain
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K1, K2, K3. K3 is synthetic.
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K1、K2 are 2-ethyl -1,4- napthalene derived
Functions:
To promote blood coagulation;
Important factors in hepatic synthesis of
thrombinogen and other blood coagulation
factors .
Carboxylation of Glu into γ-thrombinogen
depends on enzymes with Vk
Plasma thrombin
Vitamin K
thrombinogen
thromboplastic protein
Phospholipid, Ca2+
thrombin
fibrae sanguis
Unsoluble fibrin clot
Structure:
Vitamin K3
Source:
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Food:
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Vegetables, animal liver, fish
 Milk, beans
Intestinal microorganisms
3. Water-soluble vitamins
and cofactors of enzyme
3.1 Vitamin B1
Constitute of an amino pyrimidine ring and a
sulfur-containing thiazole ring
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Active form in vivo:
焦磷酸硫胺素TPP( thiamine pyrophosphate)
Structure
pyrimidine ring
thiazole ring
*
*
Functions
(1) Coenzyme for decarboxylases
(2) Coenzyme for transketolases
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Properites:
easy soluble in water, acidic.
stable in acidic solution
vulnerable to neutral and alkalic condition
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Sources:
Plant: cereals, beans
Yeast
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Unit∶
1IU≈3μg pure VB1 hydrochloride
3.2 Vitamin B2 and FMN, FAD
Vitamin B2 is also named as Riboflavin
 Green fluorescent in solution
 Part of prosthetic groups of oxidoreductase
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Structure
FMN∶ Flavin mononucleotide黄素单
核苷酸
 FAD∶Flavin Adenine Dinucleotide
黄素腺嘌呤二核苷酸
 FMN, FAD——prosthetic groups—
—tightly bind to enzyme
 Yellow →flavoprotein
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Strong oxidant that is reduced by 1 or 2 atoms:
H transfer
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Functions：
 Promote saccharide, lipid and protein metabolism as
prosynthetic group.
 Protect mucosa, maintain visual function, promote growth.
Deficiency:
 Weak respiratory system, low metabolism rate
 angular cheilitis(口角炎), glossitis(舌炎), conjunctivitis(结膜炎).
Min intake for adults: 1.6mg/d
No intoxication when overdosed.
Sources:
 Wide existence in plants
 Rice bran, yeast, liver, yolk, etc..
3.3 Pantothenic acid (Vit. B3)
& CoA-SH
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Sulfatidate bond
faciliates hydrolization
Acidic compound of
α, γ-dihydroxyl-β,
β-dimethylbutyric acid
β-alanine
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phosphonic acid
pantothenic acid
β-cysteamine
↓
4´-phosphopantetheine (4´-PPaSH)
+ 5´-adenylate-3´- phosphonic
acid
↓
CoA-SH (辅酶A）
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Functions:
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Participate in saccharide, lipid and protein
metabolism in the form of CoA-SH
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Participate in fatty acid metabolism as prosynthetic group
of acyl carrier protein
Acyl carrier of acylation and oxydation decarboxylation
（acyl- CoA：saccharide and lipid oxidation.
Synthesis of acetylcholine, cholesterol, glycogen, modulates
blood lipid.
Effective to anorexia and debilitation
Ancillary drug for hepatitis and coronary heart
disease
Sources:
Wide existence.
Liver, kidney, wheat,
rice bran, yeast
peanut.
4. Nicotinic Acid and CoⅠ,CoⅡ
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pellagra preventive factor or VPP
Nicotinic Acid(烟酸) & Nicotinamide(烟酰胺)
structure:
Oxidized form
NAD+
NADP+
Reduced form
NADH
energy yielding catabolism
oxidized by respiratory chain
NADPH
reductions in assimilation
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Functions:
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Participate in metabolism as coenzyme of anaerobic
dehydrogenase H transfer
Maintain health of neural system.
Promote growth of microorganisms
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Deficiency:
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Pellagra , diarrhea, dementia
Sources:
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Synthesized from Ser.
Yeast, liver, lean meat, milk, peanut, soybean
3.5 VB6
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吡哆醛 pyridoxal
吡哆胺 pyridoxamine
吡哆醇 pyridoxine
structure:
磷酸吡哆醛
磷酸吡哆胺
Functions
(1) Transamination
(2)
Decarboxylation
(3) Coenzyme of serine transhydroxymethylase for onecarbon unit transfer
3.6
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Biotin (Vit. B7)
Thiophene + urea
α-biotin（yolk）
——isopentoic acid side chain
β-biotin（liver）
——pentanoic acid side chain
similar chemical and physiological characters
Wide existence in both animals and plants.
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Co-enzyme/ prosynthetic group of carboxylase——CO2 fixation
e.g. pyruvate carboxylase
3.7
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Folic acid (Vit. B11)& CoF
pterolyglutamic acid(PGA)
Functions
（1）tetrahydrofolate
(CoF、FH4、THFA):
Coenzyme of singelcarbon metablism
(2) FH4 participate in pyrimidine synthesis
promote protein composition
Deficiency : anaemia
Sources:
 Green vegetables.
 Intestinal microorganisms