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Vitamins, Cofactors, Coenzymes, Enzymes - Lecture Slides - Biochemistry, Slides of Biochemistry

The Tamil Nadu Dr. M.G.R. Medical University Biochemistry

These lecture slides covers Vitamins, Cofactors, Coenzymes, Enzymes in details.

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19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 1

Ch. 3: Vitamins, Cofactors, Coenzymes, Enzymes

ØP. J. Bruice, Organic Chemistry, 2nd ed., Prentice-Hall, Upper Saddle

River, New Jersey, 1998, Chapter 22.

ØH. Dugas, Bioorganic Chemistry - A Chemical Approach to Enzyme

Action, 3rd ed., Springer Verlag, New York, 1996, chapter 7.

ØO. Isler, G. Brubacher, Vitamins I: Fat-Soluble Vitamins, Thieme

Verlag, Stuttgart, 1982.

ØO. Isler, G. Brubacher, S. Ghisla, B. Kraeutler, Vitamins II: Water-

Soluble Vitamins, Georg Thieme Verlag, Stuttgart, 1988.

Øhttp://www.indstate.edu/thcme/mwking/vitamins.html

∗Readings

Partial preview of the text

Download Vitamins, Cofactors, Coenzymes, Enzymes - Lecture Slides - Biochemistry and more Slides Biochemistry in PDF only on Docsity!

Ch. 3: Vitamins, Cofactors, Coenzymes, Enzymes

ÿ P. J. Bruice, Organic Chemistry, 2nd^ ed., Prentice-Hall, Upper Saddle

River, New Jersey, 1998, Chapter 22.

ÿ H. Dugas, Bioorganic Chemistry - A Chemical Approach to Enzyme

Action, 3rd^ ed., Springer Verlag, New York, 1996, chapter 7.

ÿ O. Isler, G. Brubacher, Vitamins I: Fat-Soluble Vitamins, Thieme

Verlag, Stuttgart, 1982.

ÿ O. Isler, G. Brubacher, S. Ghisla, B. Kraeutler, Vitamins II: Water-

Soluble Vitamins, Georg Thieme Verlag, Stuttgart, 1988.

ÿ http://www.indstate.edu/thcme/mwking/vitamins.html

∗ Readings

Glossary

vitamin (water soluble vitamin, fat soluble vitamin) : a substance

needed in small amounts for normal body functions that the body

cannot synthesize in adequat amounts

enzyme : a protein that is a catalyst
metalloenzyme : an enzyme that has a tightly bound metal ion

cofactor : an organic molecule or a metal ion that certain enzymes

need in order to catalyze a reaction or a process

coenzyme : an organic molecule (vitamin) as cofactor
prosthetic group : a cofoctor permanently associated with the

protein, often covalently bound

holoenzyme : catalytically active enzyme-cofactor complex.
apoenzyme : an enzyme without its cofactor (enzymatically inactive

protein)

Problems - 1

@ Vitamin C and Vitamin E are both natural radical inhibitors. Explain why

this is so.

@ Explain why vitamin C is a „strong“ acid

@ Ascorbinsäure can be methylated by diazomethane. Which functional

group is most sensitive towards methylation?

@ (L)-Sorbose which is an intermediate in the technical synthesis of vitamin

C, forms a furanosid by reaction with aceton/H+.

Discuss the mechanism of formation. Are there diastereotopic methyl

groups?

Problems - 2

@ Apply Woodward-Hoffmann-Rules for the synthesis of Vitamin D 3.

Sum up the WH-rules for the electrocyclic and sigmatropic reactions

under thermal respectively photochemical conditions.

a) Which stereoisomer is formed by irradiating (2E,4Z,6Z)-

octatriene?

@ Stereoselective oxidoreduction of ketones and alcohols using horse

liver alcohol dehydrogenase (HLADH) needs NADH as cofactor.

NADH is rather expensive and has to be recycled. Recyclization can

be achieved by natrium dithionite. Formulate the reaction sequence

for the keton reduction by HLADH/NADH and the subsequent

recyclization of NAD+^ by dithionite.

@ Assign the pro-R hydrogen and the pro-S hydrogen of NADH.

@ Compare typical applications of NAD+/NADH und FAD as

oxidoreductases with regard to their involvements in the biochemical

processes.

Enzymatic reactions and catalysis

Vitamins, coenzymes, cofactors, enzymes

enzyme

protein + coenzyme (vitamin)

protein + cofactor (metal ion)

Structure of water soluble vitamins

niacin nicotinic acid

HN NH

CO 2 H

biotin vitamin H

N N

N (^) S H 3 C

NH 2 H

H 3 C OH

thiamine vitamin B 1

S S

n CO^2 H n = 3 lipoate

N CH 3

CH 2 OH HOCH 2

pyridoxine vitamin B 6

HO N

Me (^) Me

O CO 2 H H

N N N

N (^) N H

H 2 N

H NH

O CO 2 H

CO 2 H

O H HO OH

H OH

CH 2 OH

H^ H

OH HO OH

Me N^ N Me N^ NH O

pantothenate folate

vitamin B 12

vitamin C ascorbic acid riboflavin vitamin B 2

subunit of CoA-SH

BO/BBM

ÿ Discovering Nature's Diverse Pathways to Vitamin B 12 : A 35-Year Odyssey: A. I.

Scott, J. Org. Chem. 2003 , 68 , 2529-2539..

Vitamin B 12 BO/BBM/SKB

Vitamin C

mp 190-192°C
pK 1 = 4.17; pK 2 = 11.
anti-scorbutically factor (essential for the synthesis of

collagen)

reducing agent in hydroxylation reactions
radical scavenger (inhibitor)

Industrial synthesis of vitamin C (Reichstein, 1934)

ÿ H. Beyer, W. Walter, Lehrbuch der Organischen Chemie , 1998.

Vitamin D

Metabolism of calcium and phosphorous
Deficiency impairs bone formation (rickets)
Excess causes calcification of soft tissues

Photochemical formation of vitamin D 3

∗ two step reaction

first step: conrotatory photochemical ring opening
second step: [1,7] sigmatropic antarafacial hydrogen shift (thermal)

∗ Woodward-Hoffmann rules

∗ Active form 1,25-dihydroxyvitamin D 3

C-1^ C-

Bioactive flavins

∗ vitamin B 2 – riboflavin

∗ flavin mononucleotide

(FMN)

∗ flavin adenine dinucleotide

(FAD)

Me N^ N

N N Me H O

Vitamins, Cofactors, Coenzymes, Enzymes - Lecture Slides - Biochemistry, Slides of Biochemistry

Related documents

Partial preview of the text

Download Vitamins, Cofactors, Coenzymes, Enzymes - Lecture Slides - Biochemistry and more Slides Biochemistry in PDF only on Docsity!

Ch. 3: Vitamins, Cofactors, Coenzymes, Enzymes

ÿ P. J. Bruice, Organic Chemistry, 2nd^ ed., Prentice-Hall, Upper Saddle

River, New Jersey, 1998, Chapter 22.

ÿ H. Dugas, Bioorganic Chemistry - A Chemical Approach to Enzyme

Action, 3rd^ ed., Springer Verlag, New York, 1996, chapter 7.

ÿ O. Isler, G. Brubacher, Vitamins I: Fat-Soluble Vitamins, Thieme

Verlag, Stuttgart, 1982.

ÿ O. Isler, G. Brubacher, S. Ghisla, B. Kraeutler, Vitamins II: Water-

Soluble Vitamins, Georg Thieme Verlag, Stuttgart, 1988.

ÿ http://www.indstate.edu/thcme/mwking/vitamins.html

∗ Readings

Glossary

needed in small amounts for normal body functions that the body

cannot synthesize in adequat amounts

cofactor : an organic molecule or a metal ion that certain enzymes

need in order to catalyze a reaction or a process

protein, often covalently bound

protein)

Problems - 1

@ Vitamin C and Vitamin E are both natural radical inhibitors. Explain why

this is so.

@ Explain why vitamin C is a „strong“ acid

@ Ascorbinsäure can be methylated by diazomethane. Which functional

group is most sensitive towards methylation?

@ (L)-Sorbose which is an intermediate in the technical synthesis of vitamin

C, forms a furanosid by reaction with aceton/H+.

Discuss the mechanism of formation. Are there diastereotopic methyl

groups?

Problems - 2

@ Apply Woodward-Hoffmann-Rules for the synthesis of Vitamin D 3.

Sum up the WH-rules for the electrocyclic and sigmatropic reactions

under thermal respectively photochemical conditions.

a) Which stereoisomer is formed by irradiating (2E,4Z,6Z)-

octatriene?

@ Stereoselective oxidoreduction of ketones and alcohols using horse

liver alcohol dehydrogenase (HLADH) needs NADH as cofactor.

NADH is rather expensive and has to be recycled. Recyclization can

be achieved by natrium dithionite. Formulate the reaction sequence

for the keton reduction by HLADH/NADH and the subsequent

recyclization of NAD+^ by dithionite.

@ Assign the pro-R hydrogen and the pro-S hydrogen of NADH.

@ Compare typical applications of NAD+/NADH und FAD as

oxidoreductases with regard to their involvements in the biochemical

processes.

Enzymatic reactions and catalysis

Vitamins, coenzymes, cofactors, enzymes

enzyme

protein + coenzyme (vitamin)

protein + cofactor (metal ion)

Structure of water soluble vitamins

subunit of CoA-SH

BO/BBM

ÿ Discovering Nature's Diverse Pathways to Vitamin B 12 : A 35-Year Odyssey: A. I.

Scott, J. Org. Chem. 2003 , 68 , 2529-2539..

Vitamin B 12 BO/BBM/SKB

Vitamin C

collagen)

Industrial synthesis of vitamin C (Reichstein, 1934)

Vitamin D

Photochemical formation of vitamin D 3

∗ two step reaction

∗ Woodward-Hoffmann rules

∗ Active form 1,25-dihydroxyvitamin D 3

Bioactive flavins

∗ vitamin B 2 – riboflavin

∗ flavin mononucleotide

(FMN)

∗ flavin adenine dinucleotide

(FAD)

Flavin Biochemistry

∗ Dehydrogenation

∗ Activation of oxygen, hydroxylation, oxygenation

∗ Electron transfer, electron transport, respiration chain,

etc.

∗ Light emission, bacterial luciferase

(bioluminescence)