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Chapter 9 vitamin and coenzyme

Chapter 9 vitamin and coenzyme. vitamin and coenzyme. 一、 Vitamin General remarks. 二、 Water-soluble vitamins. 三、 Lipid-soluble vitamins. 【 目的与要求 】. 【 the intention and need 】. B vitamins and their coenzyme. Note key. lipid-soluble vitamin deficiency. Basic command.

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Chapter 9 vitamin and coenzyme

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  1. Chapter 9 vitamin and coenzyme

  2. vitamin and coenzyme 一、 Vitamin General remarks 二、 Water-soluble vitamins 三、 Lipid-soluble vitamins

  3. 【目的与要求】 【 the intention and need】 B vitamins and their coenzyme Note key lipid-soluble vitamin deficiency Basic command General understanding concept , importance, nomenclature and classification of vitamins

  4. 4.1 维生素总论 §3.1 Vitamin General remarks 一、introduction Concept of vitamin • Vitamins are a class of low-molecule-weight organic compounds , essential for normal growth and development. Diseases • Deficiency Poisoning disease

  5. Function of vitamin • Vitamins are the organic compounds which play important roles in metabolism • essential, noncarloric, nutrient needed in tiny amounts in the diet. • Usually as enzyme cofactor ,play a significant role in regulating metabolism and maintaining physical functions.

  6. §3.1 Vitamin General remarks 三. nomenclature and classification (一) nomenclature :Custom • according to A、B、C、D……Letter • according to composition • according to physiological function

  7. §3.1 Vitamin General remarks (二) classification Water-soluble vitamins lipid-soluble vitamins

  8. 4.3 水溶性维生素 §3 water-soluble vitamin B complex group Water soluble vitamin vitamin C α lipoic acid -vitamin B group--- B1, B2, B6, B12, Vitamin PP, pantothenic acid, biotin, Folic acid, lipoic acid

  9. Vitamin and coenzyme • The B vitamin and vitamin C are water soluble . • The body absorbs these vitamins easily and just as easily excretes them in the urine . • The water-soluble vitamins are coenzymes for many common biochemical reactions . • Some help generate energy; • others help make protein and new cells . • Some vitamins are the coenzymes independently. • Some vitamins are components of coenzymes.

  10. Vitamin B1(thiamine) and cocarboxylase • Resources: husk and bud of crops, yeast, some vegetables. • Structure: a thiazole ring+ pyrimidine ring • To form thiamine. • The action site is the carbon atom in C2 of thiazole ring. • Functions: a cocarboxylase catalyzes decarboxylation reaction.

  11. Thiamine is converted to the coenzyme :Thiamine pyrophosphate (TPP)

  12. TPP: Thiamine pyrophosphate • (TPP) is the active structure of thiamine (vitamin B1) TPP is coenzyme for oxidative decarboxylase of the α-keto acid. • requires for the key reactions catalyzed by • pyruvate dehydrogenase complex • α-ketoglutarate dehydrogenase complex • for the transketolase reactions of the pentose phosphate pathway .

  13. Vitamin B1 shortage: • 1. accumulation of pyruvic acid in blood, • urea and nervous system. • 2. energy shortage in nervous system • leading to beriberi. • 3. Inhibit cholinesterase，increase in the secretion of digest solution and Intestinal peristalsis，Help digestion . lost of appetite and indigestion neuritis

  14. Vitamin B2 and lyochrom( yellow coenzyme,riboflavin) • Resources: crop husk, vegetables, animal liver and heart. milk • Structure: there are two forms of vitamin B2: • --flavin mononucleotide ( FMN) • --flavin adenine dinucleotide (FAD) • Functions: vitamin B2 is a prosthetic group of yellow enzymes. It playing an important role in oxidation-reduction reaction.

  15. O N N H3C H3C N N HCH (HCOH)3 CH2OH O flavin

  16. nitrogens 1 & 5 carry hydrogens in FADH2

  17. Vitamin B2 is the precursor of flavin adenine dinucleotide (FAD) and flavin monoucleotide (FMN) coenzymes for oxidoreductases as hydrogen transfers. both of which are involved in energy production and cellular respiration

  18. Vitamin B2 shortage • Inflammation of lip • Glossitis • Perleche • keratitis

  19. Vitamin PP and coenzyme I and II • Resources: meats, grain, peanut, mushrooms • Vitamin PP can be synthesized inside the body. The raw material for synthesis is tryptophan • Structure: two forms of compond- • - nicotinic acid or niacin • -nicotinamide or niacinamide.

  20. CONH2 COOH N N Nicotinic Acid Nicotinamide

  21. R Coenzymes for oxidoreductases **Hydride transfer-- nicotinamide ring • R=P: • NADP+: Nicotinamide adenine dinucleotide phosphate • R=OH: • NAD+: Nicotinamide adenine dinucleotide

  22. Functions: • nicotinic acid is converted to the ubiquitous oxidation-reduction coenzymes NAD+ and NADP+ in the body ,which transmit hydrogen in oxidative phosphorylation reaction • the ubiquitous coenzyme for dehydrogenases. • Some enzymes need NAD, some need NADP, • some need either NAD or NADP. • Oxidation state: • NAD or NAD+; • NADP or NADP+ • Reduction state: • NADH2 or NADH + H+; • NADPH2 or NADPH + H+

  23. + e + H+ + H + H+ H +2H NAD(P)+ NAD(P)H+H+ e -2H H H H+ 2H

  24. Vitamin PP shortage: • result pellagra. • dermatitis • diarrhea • and dementia

  25. Vitmin B6 and pyridoxal • Vitamin B6 includes three compounds: • These three compounds can change each other and can be phosphated into phosphate state. Pyridoxamine Pyridoxal Pyridoxine

  26. B 6 R CH2OH HO H3C N • Pyridine derivatives • Mechanism of catalysis: intermediate- aldimine ( Schiff’s base) avtivesite pyridoxal：R= -CHO pyridoxamine：R= -CH2NH2 pyridoxine：R= -CH2OH

  27. Pyridoxal phosphate and pyrodoxamine phosphate are main active forms in metabolism (PLP)

  28. ADP ATP CH2O kinase Pyridoxal Phosphate CH2O Pyridoxamine Phosphate CH2OH Pyridoxal Amino acids metabolism

  29. functions • The coenzyme playing important roles in amino acid metabolism • There are several classes of reactions catalyzed by pyridoxal-5-phosphate • Example: • 1. transamination: catalyze by transaminase • 2. decarbxylation • 3. racemization

  30. 磷酸吡哆醛参加的7种与氨基酸代谢有关的反应磷酸吡哆醛参加的7种与氨基酸代谢有关的反应

  31. 磷酸吡哆醛参加的7种与氨基酸代谢有关的反应磷酸吡哆醛参加的7种与氨基酸代谢有关的反应

  32. Resources: wide contribution in food, vegetable and fruits-fish, liver, eggs yolk, meat, yeast, grains • Vitamin B6 shortage: not find

  33. Pantothenic acid(B3) and CoA • Resources: tissues and organs of plants and animals. • Structure • Functions:coenzyme • a carrier of acyl-group in metabolism to form acyl-S-CoA • is a component of coenzyme A(CoA),required for the metabolism of all fat ,protein ,and carbohydrate via the citric acid cycle and for fatty acid and cholesterol synthesis .

  34. active form CoA、ACP

  35. Pantothenic acid 4’-phosphopantothenate ACP SH acyl Carrier of acyl PA β-mercaptoethylamine β-alanine Pantothenic acid Pantonic acid CoA 3’,5’-ADP

  36. The two main functions of coenzyme A are (a) activation of acyl groups for transfer by nucleophilic attack and (b) activation of the α-hydrogen of the acyl group for abstraction as a proton.

  37. CoA and ACP act as cofactors for acetyltransferases defficiency “burning feet ”

  38. O C NH HN N CH HC C H2C S （CH2）4 O O=C C=O E-NH Biotin VB7或VH biotin biocytin Carboxyl group carrier Carboxyl group is transferred to biotin to form N-carboxy-biotin N-carboxyl-biocytin COOH **Coenzyme of carboxylase enzyme

  39. Functions: • 1. fixation of CO2 • 2. carboxylation • 3. catalyze carboxylase reaction • 4. Biotinis the covalently bound prosthetic group of pyruvate carboxylase ,acetyl-CoA carboxylase • Sources: • peanuts, chocolate, eggs, etc the deficiency condition is rather rare.

  40. Folic acid Pteroylglutamic acid • Resources: abundant in green leaves (spinach, turnip) • Structure • Animals need a supply of folic acid from food.

  41. N N 1 H2N 8 2 7 10 9 3 6 N Glu CH2 NH CO 5 4 N OH PABA Folic acid VB11 pteridine p-aminobenzonic acid Folic acid

  42. positions 7 & 8 carry hydrogens in dihydrofolate (DHF)positions 5-8 carry hydrogens in tetrahydrofolate (THF)

  43. Dihydrofolate reductase Dihydrofolate reductase DHF THF NADPH+H+ NADP+ NADPH+H+ NADP+ THF: tetrahydrofolate THF is formed by two successive reductions of folate by dihydrofolate reductase THF F

  44. Gly, Ser, His • THF is a carrier of one carbon unit formyl methyl N5—CH3—FH4 folate N10—CHO—FH4 folate methylene formimino N5、N10—CH2—FH4 folate N5—CH=NH—FH4 folate

  45. Functions:Tetrahydrofolic acid (FH4) • Function: transport of mono-carbon groups • glycine to serine • purine ring synthesis • pyrimidine ring synthesis • Shortage:inhibition of DNA synthesis . • Megaloblastic macrocytic anemia

  46. Vitamin B12 • Structure: containing cobalt. It is called cobalamine. There are different forms of cobalamine. The variety is depend on the groups combing in cobalt atom • Functions: • 1. coenzyme for mutases • 2. coenzyme for metabolism of mono-carbon group

  47. B 12 CO+ nucleotide ribose P Cobalamin base CO+&N Coordination Cobalt ion Corrin ring R

  48. R= 5'-deoxyadenosyl 5'-deoxyadenosylcobalamin • Alkyl transfers R=CH3 methylcobalamin • Methyl group transfers (assisted by tetrahydrofolate - which is covered next) • required for the methionine synthesis reaction

  49. Resources and shortage • Vitamin B12 can be taken from animal source food—meats, livers, fish and eggs • Lack of Vitamin B12 may result some diseases such as pernicious anemia • irreversible nervous system damage in the fetus

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