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Glycolysis and the Catabolism of Hexoses Fates of Glucose

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Glycolysis and the Catabolism of Hexoses Fates of Glucose Glycolysis and the Catabolism of Hexoses Eduard Büchner 1860 - 1917 Fritz A. Lipmann 1899 – 1986 Sir Hans A. Krebs 1900 – 1981 (Anaerobic Fermentation) (Discovered Coenzyme A) (Citric Acid Cycle) Lipmann and Krebs shared the 1953 Nobel Prize for Physiology or Medicine Fates of Glucose Fig 15-01.GIF 1 Two phases of Glycolysis: Preparatory Phase C6 9 2 C3 Fig 15-02.GIF Two phases of Glycolysis: Energy Conservation Phase 2 C3 9 2 C3 2 ATP Fig 15-02.GIF 2 Glycolysis Stage I: Preparatory Phase (Rxn 1 & -1) HO 6 5 O "Tags" glucose to keep it in the cell ∆ BN 4 G = - 16.7 kJ/mol OH 1 OH OH 3 2 +1 - glucokinase (or hexokinase) OH -1 - glucose-6-phosphate phosphatase glucose (G) B ∆G N Pi ATP = - 13.8 kJ/mol -1 +1 Removes Pi - active only in gluconeogenesis H2O ADP PiO 6 nonliver 5 O 4 OH 1 OH OH 3 2 liver OH glucose-6-phosphate (G6P) http://www.med.unibs.it/~marchesi/glycolys.html Glycolysis Stage I: Preparatory Phase (Rxn 1) HO 6 5 O "Tags" glucose to keep it in the cell ∆ BN 4 G = - 16.7 kJ/mol OH 1 OH OH 3 2 +1 - glucokinase (or hexokinase) OH -1 - glucose-6-phosphate phosphatase glucose (G) B ∆G N Pi ATP = - 13.8 kJ/mol -1 +1 Removes Pi - active only in gluconeogenesis H2O ADP PiO 6 5 O 4 OH 1 OH OH 3 2 OH glucose-6-phosphate (G6P) http://www.med.unibs.it/~marchesi/glycolys.html 3 Glycolysis Stage I: Preparatory Phase (Rxn 2) PiO 6 5 O phosphohexose isomerase 4 OH 1 OH OH 3 2 OH glucose-6-phosphate (G6P) 2 - glucose-6-phosphate isomerase B ∆G N 2 = + 1.67 kJ/mol Isomerization of C in preparation PiO 6 O OH 6 1 for the cleavage reaction 5 OH 2 OH 4 3 OH fructose-6-phosphate (F6P) Glycolysis Stage I: Preparatory Phase (Mechanism 2a) º º º º 4 Glycolysis Stage I: Preparatory Phase (Mechanism 2b) º º º º Glycolysis Stage I: Preparatory Phase (Mechanism 2c) º º º º 1 CH2OH 2 C O O 1 HO 6 OH HOC H 3 5 OH 2 H C OH 4 4 3 OH H 5C OH OH 6CH2OH α-D-FRUCTOFURANOSE OPEN CHAIN FORM 5 Glycolysis Stage I: Preparatory Phase (Rxn 3 & -3) PiO 6 O OH 1 2nd phosphorylation to commit 5 OH glucose into glycolysis 2 B OH ∆ N 4 G = - 14.2 kJ/mol 3 OH +3 - phosphofructokinase fructose-6-phosphate (F6P) -3 - fructose-1,6-bisphosphate phosphatase Pi ATP B N -3 +3 ∆G = - 16.7 kJ/mol Removes Pi - active only in gluconeogenesis H2O ADP 1 PiO 6 O OPi OH 5 2 OH 4 3 OH fructose-1,6-bisphosphate (F6P) Glycolysis Stage I: Preparatory Phase (Rxn 4 & 5) 1 PiO 6 O OPi OH 5 2 OH 4 3 4 - aldolase OH B N ∆G = + 24.0 kJ/mol fructose-1,6-bisphosphate (F6P) Cleavage of C6 into 2 x C3 fragments 4 1 PiO 6 OH OPi OH 5 - triosephosphate isomerase 2 B N 5 + OH ∆G = - 7.6 kJ/mol 4 3 O glyceraldehyde-3-phosphate dihydroxyacetone phosphate Isomerization of C3 to interconvert forms (GAP) (DHAP) B N O ∆G = - 24.0 kJ/mol 1 4 CH OPi CH 5 2 H 5C OH 2 CO 6 3 CH2OPi CH2OH (GAP) (DHAP) (over for Stage II starting with2GAP) 6 ALDOLASE º º º º º º º º º º º º º º º º Glycolysis Stage I: Preparatory Phase (Rxn 5) glyceraldehyde-3-phosphate dihydroxyacetone phosphate (GAP) (DHAP) O 1 4 5 CH OPi CH 2 5 - triosephosphate isomerase 5 2 B N H C OH CO ∆G = - 7.6 kJ/mol 3 6 CH2OPi CH2OH Isomerization of C3 to interconvert forms (GAP) (DHAP) 7 Triosephosphate Isomerase Mechanism Glycolysis Stage II: Energy Conservation Phase (Rxn 6) ***2 x all intermediates*** O 3,4 CH 2,5 GLYCOLYSIS STAGE II: H C OH PREPARATORY PHASE 1,6CH2OPi (Energy Conservation Phase) glyceraldehyde-3-phosphate (GAP) Pi + NAD+ 6 - glyceraldehyde-3-phosphate dehydrogenase B 6 ∆G N = + 6.3 kJ/mol NADH + H+ substrate-level oxidative phosphorylation: O O process of oxidation coupled to phosphorylation - 3,4 C OPO Step 6 alone is an example which generates st 2,5 - 1 high energy phosphate compound responsible H COH O for the net 2 ATP/glucose. 1,6 CH2OPi Step 6 + Step 7 can also be considered to be substrate-level oxidative phosphorylation for the 1,3-bisphosphoglycerate (1,3-BPG) formation of ATP 8 Glycolysis Stage II: Energy Conservation Phase (Rxn 6) Fig 15-05.GIF Glycolysis Stage II: Energy Conservation Phase (Rxn 6) GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE O H O O O H H O C C H O - C O P O H2N + - C - + H C OH + HO P O H2N O + H + H C OH N OH CH2OPi N CH2OPi R glyceraldehyde-3-Pi R 1,3-bisphosphoglycerate **NAD **NADH (oxidized form) (reduced form) O INHIBITOR WITH RESPECT TO Pi: HO As O- (and uncoupler of substrate-level oxidative phosphorylation) OH 9 Glycolysis Stage II: Energy Conservation Phase (Rxn 6) GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE O H O O O H H O C C H O - C O P O H2N + - C - + H C OH + HO P O H2N O + H + H C OH N OH CH2OPi N CH2OPi R glyceraldehyde-3-Pi R 1,3-bisphosphoglycerate **NAD **NADH (oxidized form) (reduced form) ORDERED TRI BI MECHANISM NAD+ G3P Pi 1,3-BPG NADH + + E ENAD E NAD : G3P E NADH : G'3P E NADH : 1,3 BPG E NADH E Glycolysis Stage II: Energy Conservation Phase (Rxn 6) OPO - - 3 2 OPO3 2 CH2 CH2 CHOH CHOH H C O 1 C O O 4 H H O P O R N H R N O H H N N H H N N H S S - OPO3 2 - OPO3 2 CH2 CH2 2 CHOH O 3 CHOH H C P OH H O HO R N H O R N C O H N N H H H N O N H S S P HO OH O 10 Glycolysis Stage II: Energy Conservation Phase (Rxn 7) O O - 2x all intermediates in Stage II 3,4 C OPO 2,5 - H COH O 1,6 CH2OPi 1,3-bisphosphoglycerate (1,3-BPG) ADP 7 - phosphoglycerate kinase 7 B ∆ N = - 18.5 kJ/mol ATP G O - 1st energy conservation step 3,4 C O 2,5 H C OH 1,6 CH2OPi 3-phosphoglycerate (3PG) Glycolysis Stage II: Energy Conservation Phase (Rxn 8) 2x all intermediates in Stage II O - 3,4 C O 2,5 H C OH 1,6 CH2OPi 3-phosphoglycerate (3PG) 8 - phosphoglycerate mutase B ∆G N = + 4.4 kJ/mol 8 O prepares C3 for generation of - nd 3,4 C O 2 high energy phosphate compound 2,5 H C OPi 1,6 CH2OH 2-phosphoglycerate (2PG) 11 Glycolysis Stage II: Energy Conservation Phase (Rxn 8) º 2,3-BPG To control oxygen binding to Hb º º º º º º º º º http://www.med.unibs.it/~marchesi/mutase.html Glycolysis Stage II: Energy Conservation Phase (Rxn 9) O - 3,4 C O 2,5 H C OPi 1,6 CH2OH 2-phosphoglycerate (2PG) 9 9 - enolase H O H2O B 2 ∆G N = + 7.5 kJ/mol O - 3,4 C O generation of 2nd high energy phosphate compound 2,5 C OPi 1,6 CH2 phosphoenolpyruvate (PEP) Write a mechanism for the dehydration using acid/base catalysts 12 Glycolysis Stage II: Energy Conservation Phase (Rxn 10) O - Write a mechanism for the 3,4 C O phosphate transfer. What 2,5 C OPi intermediate do you have to write? What is the process 1,6 CH 2 by which that intermediate phosphoenolpyruvate (PEP) is converted to pyruvate? ADP 10 ATP 10 - pyruvate kinase B O ∆G N = - 31.4 kJ/mol - 3,4 C O 2nd energy conservation step 2,5 C O 1,6 CH3 pyruvate (PYR) Glycolysis Stage II: Energy Conservation Phase (Rxn 11) 11 - lactate dehydrogenase B ∆G N = - 25.1 kJ/mol O O Regeneration of active oxidant - - 3,4 O 3,4 O + C C + NAD NADH + H 2,5 2,5 HO C H C O 11 1,6 1,6 CH3 CH3 L-lactate (LAC) pyruvate (PYR) Write a mechanism for the reduction of pyruvate to L-lactic acid 13.
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