Lecture 12 (2009)

Lecture 12 (2009) - Lecture 12 Regulation of...

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Unformatted text preview: Lecture 12 Regulation of gluconeogenesis/glycolysis Synthesis of other carbohydrates The Pentose Phosphate Pathway Carbon assimilation in photosynthesis (Calvin Cycle) Cycle The "Powertrain" of Human Metabolism (Overview) CARBOHYDRATES PROTEINS LIPIDS Glucose Amino acids Fatty acids Other Carbohydrates Oxaloacetate GNG Glycogen Glucose-6-P Pyruvate Acetyl-CoA NADH ATP Lactate Ketone bodies Ribose-5-P NADPH NADH Cholesterol p. 21 The "Powertrain" of Human Metabolism (Overview) CARBOHYDRATES PROTEINS LIPIDS Glucose Amino acids Fatty acids Other Carbohydrates Oxaloacetate GNG Glycogen Glucose-6-P Pyruvate Acetyl-CoA NADH ATP Lactate Ketone bodies Ribose-5-P NADPH NADH Cholesterol p. 21 Gluconeogenesis: CHO H HO H H OH H HO By-pass reactions and enzymes CHO OH CH2OH O 1 CH2OPO322 O 1 CH2OPO322 O DHAP 1 H OH OH CH2OH 2 H OH OH CH2OPO32HO H H H OH OH CH2OPO32- 3 HO 3 4 5 6 4 H OH OH CH2OPO32H 3 CH2OH + 4 HC 5 O ATP ADP H H ATP ADP H H 5 OH G-3-P Haworth projection Ring form GLC GLC-6-P F-6-P F-1,6-bisP 6 CH OPO 22 3 3. By-pass CH2OH H OH OH H OH O H OH H CH2OPO32O OH 2. By-pass O3POH2C H O OH OH OH H CH2OH O3POH2C H O OH OH OH H CH2OPO32- OH H OH HPO42- 1 ATP OH H 2 H 3 ATP ADP H 6 NAD+ NADH + H+ ADP 2 Molecules -O - C O O C O -O -O OPO32C O C O 10 O OPO32CH2 9 H OPO32- 8 H OH CH2OPO32- 7 H 3,4 2,5 1,6 C O OH CH3 ATP ADP H2O CH2OH ATP ADP CH2OPO32- PYR PEP 2-PGA 3-PGA 1,3 bisPGA 1. By-pass p. 25 First By-pass Reaction (Summary) Go' = +32 kJ mol-1 G = + 23 kJ mol-1 Pyr Kinase Does not work Pyr Pyruvate Carboxylase +ATP CO2 PEP PEP Carboxykinase +GTP OAA Go' = 0.9 kJ mol-1 G = - 25 kJ mol-1 CO2 Stoichiometry of Glycolysis (G ca. - 63 kJ mol-1) 1 Glc + 2 ADP + 2 Pi + 2 NAD+ 2 Pyr + 2 ATP + 2 NADH + 2 H2O Stoichiometry of Gluconeogenesis (G ca. -16 kJ mol-1) 2 Pyr + 4 ATP + 2 GTP + 2 NADH + 6 H2O 1 Glc + 4 ADP + 2 GDP + 2 NAD+ + 6 Pi Extra Cost of Gluconeogenesis: 4 ATP per glucose Glucose Blood Cytosol Lactate Lactate Glucose Glc-6-P Phosphatase NAD+ Mitochondria NADH NAD+ F1,6BP PEP Pyr Pyr G6P F6P Fru-1,6-BP Phosphatase OAA Glycolysis-specific PEP Liver Gluconeogenesis-specific Shared (reversible) reactions Reciprocal Regulation of Glycolysis and Gluconeogenesis Pyruvate Lactate Pyr Kinase PC PEP-CK (+) AMP, NAD+, CoA (-) ATP, NADH, Acetyl-CoA Acetyl-CoA (+) ADP (-) ATP, NADH, Citrate, Succinyl-CoA PEP Oxalaoacetate Citrate (+) allosteric activation (-) allosteric inhibition Malate TCA Cycle Isocitrate (+) ADP, NAD+ (-) ATP, NADH Fumarate -Ketoglutarate (+) AMP (-) ATP, NADH, Succinyl-CoA Glucose Succinyl-CoA Activtation of Gluconeogenesis at "First By-pass" Pyruvate (+) AMP, NAD+, CoA (-) ATP, NADH, Acetyl-CoA Lactate (+) Acetyl-CoA (-) ADP Acetyl-CoA (+) ADP (-) ATP, NADH, Citrate, Succinyl-CoA PEP (-) ADP Oxalaoacetate Citrate (+) allosteric activation (-) allosteric inhibition Malate TCA Cycle Isocitrate (+) ADP, NAD+ (-) ATP, NADH Fumarate -Ketoglutarate (+) AMP (-) ATP, NADH, Succinyl-CoA Glucose Succinyl-CoA Activation of Glycolysis at "Pyruvate Kinase Reaction" Pyruvate (+) F1,6BP (-) ATP (-) Alanine (+) AMP, NAD+, CoA (-) ATP, NADH, Acetyl-CoA Acetyl-CoA Pyr Kinase (+) ADP (-) ATP, NADH, Citrate, Succinyl-CoA PEP Oxalaoacetate Citrate (+) allosteric activation (-) allosteric inhibition Malate TCA Cycle Isocitrate (+) ADP, NAD+ (-) ATP, NADH Fumarate -Ketoglutarate (+) AMP (-) ATP, NADH, Succinyl-CoA Glucose Succinyl-CoA p. 49 Reciprocal Regulation of Glycolysis and Gluconeogenesis Pyruvate Lactate Pyr Kinase PC PEP-CK (+) AMP, NAD+, CoA (-) ATP, NADH, Acetyl-CoA Acetyl-CoA (+) ADP (-) ATP, NADH, Citrate, Succinyl-CoA PEP Oxalaoacetate Citrate (+) allosteric activation (-) allosteric inhibition Malate TCA Cycle Isocitrate (+) ADP, NAD+ (-) ATP, NADH Fumarate -Ketoglutarate (+) AMP (-) ATP, NADH, Succinyl-CoA Glucose Succinyl-CoA Reciprocal Regulation of Glycolysis and Gluconeogenesis (First by-pass) (+) allosteric activation (-) allosteric inhibition Glycolysis (+) F1,6BP (-) ATP (-) Alanine ATP ADP + HPO43- Pyr kinase Phosphoenolpyruvate PEP CK (-) ADP Pyruvate PC OAA (+) Acetyl CoA (-) ADP Gluconeogenesis p. 63 Reciprocal Regulation of Glycolysis and Gluconeogenesis (Second by-pass) (+) allosteric activation (-) allosteric inhibition Glycolysis (+) F2,6BP (+) AMP (-) ATP (-) Citrate ATP ADP + HPO43- PFK-1 Glucose Fructose-6-P FBPase (+) Citrate (-) AMP (-) F2,6BP Fructose-1,6-BP HPO43- H2O Gluconeogenesis p. 63 Glycolysis CHO H HO H H OH H HO CHO OH CH2OH O 1 CH2OPO322 O 1 CH2OPO322 O DHAP 1 H OH OH CH2OH 2 H OH OH CH2OPO32HO H H H OH OH CH2OPO32- 3 HO 3 4 5 6 4 H OH OH CH2OPO32H 3 CH2OH + 4 HC 5 O ATP ADP H H ATP ADP H H 5 OH G-3-P Haworth projection Ring form GLC GLC-6-P F-6-P F-1,6-bisP 6 CH OPO 22 3 ATP Pi F-6-P 2-kinase (PFK-2) Bifunctional Enzyme ADP H2O F-2,6-bisP Phosphatase F-2,6-bisP "Dead-end" metabolite F-2,6-bisP functions only as an allosteric effector! Activity of bifunctional enzyme is reciprocally controlled (hormones, metabolites) Phosphofructokinase-1 High AMP + F2,6BP + F2,6BP PFK-1 Activity No allosteric effector High Citrate or high ATP F6P Concentration p. 64 Fructose Bisphosphatase High Citrate FBPase Activity No allosteric effector High AMP or high F2,6BP F1,6BP Concentration p. 64 Reciprocal Regulation of Glycolysis and Gluconeogenesis (Second by-pass) Glycolysis ATP (+) F2,6BP (+) AMP (-) ATP (-) Citrate ADP + HPO43- PFK-1 Glucose Fructose-6-P FBPase (+) Citrate (-) AMP (-) F2,6BP Fructose-1,6-BP HPO43- H2O Gluconeogenesis p. 63 Flux Control by Substrate Cycles (+) F2,6BP (+) AMP (-) Citrate PFK-1 Glucose-6-P Fructose-6-P FBPase Fructose-1,6-BP (+) Citrate (-) AMP (-) F2,6BP Flux Control by Substrate Cycles + 80% (+) F2,6BP (+) AMP (-) Citrate PFK-1 Glucose-6-P Fructose-6-P FBPase Fructose-1,6-BP - 80% (+) Citrate (-) AMP (-) F2,6BP Regulation Glucose TCA Cycle G6Pase Hexokinase PFK-1 Pyr Kinase Acetyl-CoA G6P F6P F1,6BP PEP Pyr Pyr PC F1,6BPase OAA F2,6BP PEP-CK PEP Hexokinase (Cytosol) G6Pase (Endoplasmic reticulum) Reciprocal regulation by: F2,6BP (activ. / inhib.) ATP (inhib. / activ.) Citrate (inhib. / activ.) Other Reciprocal regulation by: ATP (inhib. / activ.) 3. By-pass 2. By-pass 1. By-pass Feedback Control ("Acceptor Control") Allosteric Activation Glucose PFK-1 PK Glycogen Glucose-6-P Pyruvate PDH Acetyl-CoA CS IDH KGA-DH NADH ADP ETC ATP Lactate Allosteric Inhibition Synthesis of Other Carbohydrates CARBOHYDRATES PROTEINS LIPIDS Glucose Amino acids Fatty acids Other Carbohydrates Oxaloacetate GNG Glycogen Glucose-6-P Pyruvate Acetyl-CoA NADH ATP Lactate Ketone bodies Ribose-5-P NADPH NADH Cholesterol p. 21 Activation of Sugars for Biosynthesis 1. Sugar phosphate + NTP NDP-Sugar + Pyrophosphate (PPi) Glucose-1-P + UTP UDP-Glucose + PPi (see page 37) HOWEVER, the first reaction is sequentially coupled to the hydrolysis of PPi 2. Pyrophosphate (PPi) + H2O 2 Phosphate (2 Pi) NDP-Group: - Nucleoside DiPhosphate is typically UDP or ADP - NDP-sugar formation is irreversible (PPi hydrolysis) - Serves as a "recognition tag" for biosyntheses - Facilitates substrate binding - Excellent leaving group in nucleophilic reactions Source of UDP-Glucose O HN CH2OH O OH OPO32OH OH O -O P O OO P O OO P O OH O O OH OH N + -D-Glc-1-P 25 UTP O CH2OH O OH HN O P O OH O O OH OH N O -O P OO O P OO- + OH O OH O P O O- Pyrophosphate (PPi) H2O 26 2 x Phosphate (Pi) UDP-Glc p. 37 Glycogen and Starch Biosynthesis CH2 OH O OH OH OH O O OPO PO OOUDP CH2OH O 4 OH HO H OH H CH2OH O OH H H+ H OH H OH CH2 OH O 4 OH H H 1 O H OH H CH2 OH O OH H O H OH H CH2 OH H O OH H O H OH Amylose H H CH2OH O OH H O H O OH H OH Primer O HN O N O HOH OH Reducing "end" H H 1 O H CH2OH O H OH H O H UDP-Glucose CH2OH O HO OH HO H p. 65 Glycogen and Starch Biosynthesis 7 6 5 4 3 2 1 Branching Enzyme 7 6 5 4 3 2 1 Glycogen or Starch (Amylopectin) p. 65 Glucose Blood Cytosol Glucose Glc-6-P To Glycolysis UTP 2Pi PPi Glc-1-P UDP-Glc UDP Glycogen Synthase Glycogen Phosphorylase Glycogen Skeletal Muscle Liver Cellulose Biosynthesis (14) glycosidic bonds p. 66 Cellulose Biosynthesis p. 66 Cellulose Biosynthesis p. 66 Cellulose Biosynthesis Lactose Biosynthesis CH2OH O OH HO HO OH glucosyl CH2OH H O OH H OH O HN H OH Glucose + O OH CH2OH O OH O O P O OH OO P O O- galactosyl CH2OH O OH OH OH O O OH N + UDP OH Lactose UDP-Galactose p. 67 Sucrose Biosynthesis UDP-Glucose CH2OH O OH O OH OH O P O OHN O P O OH O O OH O glucose (1 2) fructose N H CH2OH O OH H H CH2OH O OH H OH O HOH2C OH H CH2OH H OH H H glucosyl OH OH H OH O 2-O 3POH2C H2O OH H 2- O3POH2C H H OH O OH H CH2OH UDP H O H O OH fructosyl CH2OH OH Fructose-6-P Sucrose Phosphate Sucrose p. 67 The "Powertrain" of Human Metabolism (Overview) CARBOHYDRATES PROTEINS LIPIDS Glucose Amino acids Fatty acids Other Carbohydrates Oxaloacetate Glycogen Glucose-6-P Pyruvate Acetyl-CoA NADH ATP PPP Lactate Ketone bodies Ribose-5-P NADPH NADH Cholesterol p. 21 The Pentose-Phosphate Pathway (PPP) or The Hexose-monophosphate Shunt The Pentose Phosphate Pathway: Functions 1. Production of NADPH 2. Biosynthesis and degradation of ribose 3. Biosynthesis/degradation of other sugars (C3 C4 C5 C6 C7 sugars) Determined by cell-specific needs for NADPH, ATP, sugars Roles for NADPH 1. Reductant in biosynthetic reactions (e.g., fatty acid synthesis, steroid synthesis) 2. Separation of catabolic and anabolic steps (e.g., in cytosol: low NADH, but high NADPH) 3. Regulation of redox homeostasis (e.g., erythrocytes, detoxification reactions) 4. Production of reactive oxygen species (ROS) (e.g., innate immune response) The Pentose Phosphate Pathway: Reactions (Cytosol) 1. Oxidation Phase (C6 C5 + CO2) 2. Isomerization Phase (C5 C5) 3. Rearrangement Phase (xC5 yC6) Phase 1: Oxidative Reactions Phase I NADP+ NADPH + H+ CH2OPO32O H OH H OH OHH OH H2O H HO H 2 H CH2OPO32O H O OH H OH H OH 6-P-Glucono--lactone COOOH H OH OH CH2OPO326-P-Gluconate H H C OH O H H OH 3 H H NADP+ NADPH + H+ H COOOH O OH OH CH2OPO32- 1 Glc-6-P Glc-6-P Dehydrogenase + CO2 OH CH2OPO32- Phase II Lactonase Ribulose-5-P (Ru5P) 6-Phosphogluconate Dehydrogenase p. 68 Phase 1: Oxidative Reactions (Summary) 6 Glc-6-P 6 Ru-5-P + 6 CO2 + 12 NADPH Phases 2 and 3: Isomerization and Rearrangement Reactions (Preview) 6 Ru-5-P 6 Pentoses (30 Carbons) Triose Pentose Heptose 5 Glc-6-P 5 Hexoses (30 Carbons) Tetrose Hexose Phase 2: Isomerization Reactions Phase II H H C OH O H H OH OH CH2OPO324 HC O H OH H H OH OH CH2OPO32Ribose-5-P H H C OH O H H OH OH CH2OPO32Ru5P 5 HO H Ribulose-5-P (Ru5P) H H C OH O H OH CH2OPO32Xylulose-5-P (Xu5P) Ru5P Phosphopentose Isomerase Phosphopentose Epimerase p. 68 Phase 3: Carbon-transfer or Rearrangement Reactions Transketolase Phase III H H C OH O HO H H OH CH2OPO32Xu5P + HC O H OH H OH H OH CH2OPO3 2R5P H H C OH HO 6 H H H O H OH OH + OH CH2OPO32Sedoheptulose-7-P CH2OH Transaldolase HO 7 H C O H OH CH2OPO3 2GA3P H H H O OH OH CH2OPO32Erythrose-4-P (E4P) CH2OH O HO H OH OH CH2OPO32F6P + H H O H OH OH CH2OPO3 2F6P C5 C5 H H C OH O + HO H H OH CH2OPO32Xu5P C6 H H H O OH 6 OH CH2OPO32E4P H C O H OH CH2OPO32GA3P H + H C5 Transketolase C3 C6 p. 68 Phase 3: Carbon-transfer Reactions (Summary) 2 Xu5P + R5P 2 F6P + GA3P 2 Rounds 4 Xu5P + 2 R5P 4 F6P + 2 GA3P Gluconeogensis 5 Glucose-6-P Overall Stoichiometry of Pentose Phosphate Pathway 6 Glc-6-P + 12 NADP+ + 6H2O 6 CO2 + 12 NADPH + 12H+ + 4 F6P + 2 GA3P 6 Glc-6-P + 12 NADP+ + 7H2O 6 CO2 + 12 NADPH + 12H+ + Pi + 5 Glc-6-P 1 Glc-6-P + 12 NADP+ + 7H2O 6 CO2 + 12 NADPH + 12H+ + Pi Overall Stoichiometry of Glycolysis/PDH/TCA Cycle 1 Glc + 6 H2O + 10 NAD+ + 2 FAD 6 CO2 + 10 NADH + 10H+ + 2 FADH2 (plus 4 ATP from substrate-level phosphorylation) ...
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This note was uploaded on 09/06/2009 for the course BIS 103 taught by Professor Abel during the Spring '08 term at UC Davis.

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