Sinh học khám phá 2 Vitamins, Cofactors, Coenzymes, Enzymes

19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 1 Ch. 3: Vitamins, Cofactors, Coenzymes, Enzymes Ø P. J. Bruice, Organic Chemistry, 2 nd ed., Prentice-Hall, Upper Saddle River, New Jersey, 1998, Chapter 22. Ø H. Dugas, Bioorganic Chemistry - A Chemical Approach to Enzyme Action, 3 rd ed., Springer Verlag, New York, 1996, chapter 7. Ø O. Isler, G. Brubacher, Vitamins I: Fat-Soluble Vitamins, Thieme Verlag, Stuttgart, 1982. Ø O. Isler, G. Brubacher, S. Ghisla, B. Kraeutler, Vitamins II: Water- Soluble Vitamins, Georg Thieme Verlag, Stuttgart, 1988. Ø http://www.indstate.edu/thcme/mwking/vitamins.html ∗ Readings 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 2 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) 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 3 Glossary • metabolism: reactions that living organism carry out • catabolism: energy and simple molecules are formed from complex molecules • anabolism: synthesis of complex biomolecules using energy 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 4 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? 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 5 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. 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 6 Problems - 3 @ Nature exploits the reactivity of C-8 methyl group of flavins in order to link to the apoenzyme via a SH group of a cystein. The overall process is as given below. The last step is the oxidation of the cystein bound FADH 2 to enzyme-FAD. N N Me N N Me H O O R N N CySCH 2 N N Me H O O R CyS - @ Discuus the similarity of decarboxylation of a β-keto acid and enzymatic pyruvate decarboxylation. @ The pyrimidine-amino-group in thiamin pyrophosphate contributes in the enzymatic TPP-dependent processes. How can this be explained? 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 7 Enzymatic reactions and catalysis 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 8 Vitamins, coenzymes, cofactors, enzymes enzyme protein + coenzyme (vitamin) protein + cofactor (metal ion) 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 9 Vitamins, coenzymes, enzymes cofactors Vitamins that are coenzyme precursors Ø D. Voet, J. G. Voet, Biochemistry, second edition ed., John Wiley & Sons, New York, 1995. 19.07.04 lcns_03k03aw.ppt - SBO/SS 2003 10 Structure of water soluble vitamins N OH O niacin nicotinic acid S NH HN O 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 CO 2 H n n = 3 lipoate N CH 3 OH CH 2 OH HOCH 2 pyridoxine vitamin B 6 N HO Me Me OH O CO 2 H H N N N N N H O H 2 N H N H O CO 2 H CO 2 H O H HO OH O OH H C H 2 O H H H H OH OH OH OH N N Me N N Me H O O pantothenate folate vitamin B 12 vitamin C ascorbic acid riboflavin vitamin B 2 subunit of CoA-SH BO/BBM [...]... B 12 Ø Discovering Nature's Diverse Pathways to Vitamin B 12: A 35-Year Odyssey: A I Scott, J Org Chem 20 03, 68, 25 29 -25 39 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 11 BO/BBM Fat soluble vitamins CH3 O HO CH3 H3C CH3 O n CH3 O vitamin E α-tocopherol n=3 vitamin K1 Me Me CH2OH Me Me vitamin A (all-trans) H HO vitamin D3 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 12 Vitamin C • mp 190-1 92 C • pK1 = 4.17; pK2... SBO/SS 20 03 20 Flavin structure Ø F Müller, Chemistry and Biochemistry of Flavoenzymes, Vol I, CRC, Boca Raton, 1991 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 21 Isoalloxazine synthesis 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 22 Redox processes of flavins (electron transfer/protonation) R1 R1 R2 N O N N N H red R1 R2 N R1 N O Fl-red Flox O N N H+ H R1 R2 N R1 N H N O N H O O FlHrad red R1 R1 R2 N N H... H O FlH2 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 R1 R2 N R1 N H N O N H O FlH-red 23 Some enzymatic processes of flavin nucleotides • dihydrolipoyl dehydrogenase • L-amino acid oxidase • succinate dehydrogenase • NADH dehydrogenase • luciferase catalyzed bioluminescence 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 24 Enzymatic processes of flavin nucleotides 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 25 8α-S-Cysteinylflavin:... morphogenesis ∆ S Crosson, K Moffat, 20 01 ∆ See also: http://www.uniregensburg.de/Fakultaeten/nat_Fak_III/GK/SP/download/Kottke _Phototropins.pdf 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 31 Pyruvate decarboxylase – cofactor thiamine pyrophosphate (TPP) O O O H3C H3C O NH2 H3C CO2 H + N N H + S N HC 3 O P O O O O P O O thiamine pyrophosphate TPP 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 32 Pyruvate decarboxylase 19.07.04... lcns_03k03aw.ppt - SBO/SS 20 03 33 Benzoin-type condensation – compare its mechanism to TPP catalyzed processes (transketolase) H 2 R R H O H R O 19.07.04 O CN lcns_03k03aw.ppt - SBO/SS 20 03 34 Enzyme bound biotin O HN H N E NH O S E: enzyme 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 35 Biotin – catalyzes carboxylation as a CO2 carrier ∗ carboxylation of activated carbon 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 36 ... excited state hν Ground state hν = Ee − E g lcns_03k03aw.ppt - SBO/SS 20 03 28 Bioluminescence light 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 29 Bacterial bioluminescence AA • enzyme catalyzed reaction: luciferase • reaction cascade ultimately leads to the formation of the excited state (S1) of 4ahydroxyflavin 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 30 LOV domain of Phototropin • Genetic information translated... 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 16 Photochemical formation of vitamin D3 C -25 C-1 ∗ 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 D3 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 17 Oxidoreduction: Pyridine nucleotide coenzymes (NAD+/NADP+) (Vitamin... SBO/SS 20 03 25 8α-S-Cysteinylflavin: Binding of flavins at the protein α 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 26 FAD-dehydrogenase – oxidation of a dithiol O O SH + O dihydrolipoyl dehydrogenase FAD O S SH + FADH2 S H+ R Me N Me N N O N S S H R O H+ S S 19.07.04 R lcns_03k03aw.ppt - SBO/SS 20 03 27 Bioluminescence • • • • • • • • • • • • Photoluminescence Chemoluminescence Bioluminescence Triboluminescence... hydroxylation reactions • radical scavenger (inhibitor) 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 13 Industrial synthesis of vitamin C (Reichstein, 1934) Ø H Beyer, W Walter, Lehrbuch der Organischen Chemie, 1998 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 14 Enzymatic synthesis of vitamin C 19.07.04 lcns_03k03aw.ppt - SBO/SS 20 03 15 Vitamin D • Metabolism of calcium and phosphorous • Deficiency impairs bone formation... stereochemistry (Prochirality) H(R) H3C 19.07.04 H(S) OH H(R) and H(S) enantiotopic hydrogens lcns_03k03aw.ppt - SBO/SS 20 03 18 Bioactive flavins H O ∗ vitamin B2 – riboflavin ∗ flavin mononucleotide OH HO OH (FMN) ∗ flavin adenine dinucleotide N Me O N N N H O (FAD) 19.07.04 Me lcns_03k03aw.ppt - SBO/SS 20 03 19 Flavin Biochemistry ∗ Dehydrogenation ∗ Activation of oxygen, hydroxylation, oxygenation ∗ Electron