Midterm 1 (in class) February 1 (next Thur) (bring calculator, log functions) Review Sessions MN (1/29): WED (1/31): 212 Veihmeyer, 4-6 p.m. 198 Young, 6-8 p.m.
Lecture 7 Pyruvate Dehydrogenase (PD)) omplex Tricarboxylic Acid (TA) ycle (Anaplerotic Reactions)
Enzymes for onverting ther arbohydrates into Intermediates of Glycolysis ydrolases (di-, oligo-, and polysaccharides) Kinases (phosphotransferases; phosphorylation ) Isomerases (ketol isomerases, epimerases, mutases) Dehydrogenases (NAD-dependent) Review
Intestinal Tract Dietary Polysaccharides (Starch, Glycogen) Liver, Skeletal Muscles Intracellular Polysaccharides (Glycogen Reserve) ydrolysis (unregulated) Synthesis (ATP-dep.) Phosphorolysis (highly regulated) Glucose Glucose Glc-1-P (Glycolysis) Blood Glucose
Intestinal Tract Liver, Skeletal Muscles Polymers (Proteins, Lipids, ) Intracellular Polymers ydrolysis (unregulated) Synthesis (ATP-dep.) Degradation (highly regulated) Monomers Monomers Monomers Blood Amino acids, fatty acids, sugars
Glucose 2NAD + 2 2 2ATP 2NAD + + ytosol Glycolysis 2x Pyruvate 2x Pyruvate 2ATP 8NAD + 8NAD + + Mitochondria Pyruvate Dehydrogenase Review 6x 2 TA ycle
The Pyruvate Dehydrogenase (PD) omplex A. Additional oenzymes Flavin Adenine Dinucleotide (FAD) Lipoic Acid (Lipoamide( Lipoamide) oenzyme A (oa( oa-s) Review
B. Reactions of the Pyruvate Dehydrogenase omplex verall Reaction Pyruvate + NAD + + oa-s Acetyl-oA + 2 + NAD + + ( G o = - 33.5 kj mol -1 ) TPP FAD Five o-factors: E1 E3 S S NAD + oenzyme A E2 TPP Lipoic Acid FAD cwx.prenhall.com p. 43
NAD + NAD + + 6 Pyruvate 2 1 TPP FAD 2 TPP FAD TPP FAD 3 E1 E3 E1 E3 E1 E3 S S S S S S 5 E2 TPP FAD E2 TPP FAD E2 TPP FAD 2 3 E1 E3 S S E1 E3 E1 S S E3 S 3 E2 E2 S E2 4 3 Acetyl-oA oa-s p. 43
. Mechanism of Pyruvate Dehydrogenase (E1) R 1 "Business end" of TPP is thioazolium ring N 3 S R2 R 1 3 N S arbanion R2-3 R 1 N 3 3 S R2 2 R 1 N 3 Intermediates common to both PD and PD enzymes 3 R 2 S - p. 44
R 1 N 3 3 R 2 S 2 R 1 N 3 Intermediates common to both PD and PD enzymes 3 R 2 S - S S ( 2 ) 4 Lipoamide N Enzyme (E2) 3 3 R2 R 1 N + S S S ( 2 ) 4 N Enzyme (E2) oenzymea (oa or oas) 3 ScoA + S S ( 2 ) 4 N E2 FAD 2 FAD NAD + Acetyl-oA NAD + + p. 44
Glucose 2NAD + ytosol 2 2 2ATP 2NAD + + Glycolysis 2 Pyruvate 2 Pyruvate 2NAD + 2oA-S Mitochondria 2 2 2NAD + + PD omplex 2 Acetyl-oA
verall Goal: 6 12 6 + 6 2 6 2 + 6 2 ARBYDRATES Glucose ther arbohydrates Glycolysis PD TA ycle 2 Glycogen Glucose-6-P Pyruvate Acetyl-oA NAD ATP 2 (2x) 2 (4x) 2 Lactate (1 x Glucose) p. 21
Tricarboxylic Acid (TA) ycle (itric Acid ycle; Krebs ycle) xidation of Acetyl-oA to 2 Generation of NAD and FAD 2 Substrate-level phosphorylation
2 Acetyl-oA 6NAD + 2FAD Mitochondria 2ATP 4 2 2FAD 2 TA ycle 6NAD + + 4 2 Why are so many reactions (8) required? Why are they arranged in a cycle?
2 Acetyl-oA 6NAD + 2FAD Mitochondria 2ATP 4 2 2FAD 2 TA ycle 6NAD + + 4 2 1. Dual function (catabolic and anabolic, or amphibolic) 2. Logistics of - bond cleavage (not a simple feat) 3. Requirement of sequential oxidation steps
oa-s ow to break a - bond? In biological systems, - cleavage is assisted by a proximal ( β ( position) carbonyl group (or analogous group). TA cycle intermediates provide a scaffold α β
The Tricarboxylic Acid (TA) ycle AETYL-oA 3 ScoA oa-s + + 2 2 2 2 2 2 2 2 2 1 ITRATE cis-aconitate enzyme-bound NAD ISITRATE 2 3 NAD + 2 NAD + + XALAETATE 8 2 α-ket- GLUTARATE NAD 4 NAD + oa-s NAD + + 2 MALATE 7 2 - FUMARATE FAD 2 6 FAD 2 2 SUINATE oas 5 GTP GDP + Pi 2 ScoA SUINYL-oA p. 45
Reaction 1: itrate synthase G o = - 32 kj mol -1 AETYL-oA 3 ScoA 2 oa-s + + 1 2 2 ITRATE Importance of activated acetate (Acetyl-oA oa) 2 XALAETATE p. 45
Reaction 2: Aconitase (Isomerization) G o = + 13.3 kj mol -1 + 2 2 2 ITRATE 2 2 2 2 cis-aconitate enzyme-bound 2 ISITRATE Tertiary alcohol Secondary alcohol p. 45
Reaction 3: Isocitrate Dehydrogenase (ID) G o = - 21 kj mol -1 2 α β ISITRATE 3 NAD NAD + 2 xidative Decarboxylation 2 α-ket- GLUTARATE p. 45
Reaction 4: α-ketoglutarate Dehydrogenase (KD) G o = - 33 kj mol -1 2 α-ket- GLUTARATE 4 NAD + oa-s NAD + + 2 xidative Decarboxylation 2 ScoA SUINYL-oA p. 45
Reaction 5: Succinyl-oA Synthetase (Substrate-level phosphorylation) G o = - 3 kj mol -1 2 2 oas 5 GTP GDP + Pi 2 ScoA SUINATE SUINYL-oA GTP + ADP GDP + ATP Nucleoside diphosphate kinase ( G o = 0 kj mol -1 ) p. 45
Reaction 6: Succinate Dehydrogenase (SD) G o = 0 kj mol -1 MALATE xidoreduction 7 2 - FAD 2 6 FAD 2 2 FUMARATE SUINATE p. 45
Reaction 7: Fumarase G o = - 4 kj mol -1 Addition of 2 (stereospecific, only L-MalateL Malate) MALATE 7 2 - FAD 2 6 FAD 2 2 FUMARATE SUINATE p. 45
Reaction 8: Malate Dehydrogenase (MD) AETYL-oA 3 ScoA 2 oa-s + + 1 2 2 ITRATE 2 XALAETATE NAD + + 8 G o = + 30 kj mol -1 NAD MALATE p. 45
Reaction 1: itrate synthase G o = - 32 kj mol -1 AETYL-oA 3 ScoA 2 oa-s + + 1 2 2 ITRATE 2 XALAETATE Reaction 8: MD NAD + + 8 G o = + 30 kj mol -1 NAD MALATE p. 45
The Tricarboxylic Acid (TA) ycle AETYL-oA 3 ScoA oa-s + + 2 2 2 2 2 2 2 2 2 1 ITRATE cis-aconitate enzyme-bound NAD ISITRATE 2 3 NAD + 2 NAD + + XALAETATE 8 2 α-ket- GLUTARATE NAD 4 NAD + oa-s NAD + + 2 MALATE 7 2 - FUMARATE FAD 2 6 FAD 2 2 SUINATE oas 5 GTP GDP + Pi 2 ScoA SUINYL-oA p. 45
Acetyl-oA Isocitrate Round 1 AA 2 Succinate α-kga 2
Acetyl-oA Isocitrate Round 2 AA 2 Succinate α-kga 2
Acetyl-oA Isocitrate Round 3 AA 2 Succinate α-kga 2
Acetyl-oA Isocitrate Round 1 AA 2 Succinate α-kga 2
Total ATP Glucose 2 Pyruvate 2 ATP 2 NAD 2 + 6 2 Pyruvate 2 Acetyl-oA + 2 2 2 NAD 6 2 Acetyl-oA 4 2 2 ATP 6 NAD 2 FAD 2 2 + 18 4 xidative ADP phosphorylation: 1 NAD = 3 ATP 1 FAD 2 = 2 ATP 38 ATP
The Pasteur Effect Glucose Glycolysis PD TA ycle ET 2 Glucose-6-P Pyruvate Acetyl-oA NAD ATP 2 2 2 38 ATP Aerobic onditions: Low Glucose onsumption
Glucose Glucose Glucose Glucose Glucose Glucose The Pasteur Effect Glycolysis Glucose-6-P Pyruvate 2 ATP Ethanol Anaerobic onditions: igh Glucose onsumption
The Tricarboxylic Acid (TA) ycle AETYL-oA 3 ScoA oa-s + + 2 2 2 2 2 2 2 2 2 1 ITRATE cis-aconitate enzyme-bound NAD ISITRATE 2 3 NAD + 2 NAD + + XALAETATE 8 2 α-ket- GLUTARATE NAD 4 NAD + oa-s NAD + + 2 MALATE 7 2 - FUMARATE FAD 2 6 FAD 2 2 SUINATE oas 5 GTP GDP + Pi 2 ScoA SUINYL-oA p. 45
ommon Metabolic Motifs of the TA ycle Reactions 1-3 AA α-kga Introduction of (- 2 -) group hain elongation (e.g., amino acid biosynthesis) Reaction 4 α-kga-d Decarboxylation of α-ketoacids (e.g., pyruvate) Reaction 5 Succinyl-oA synthetase Substrate-level phosphorylation (ATP) Reactions 6-8 Succinate AA Introduction of a keto function (e.g., fatty acid degradation)
Fuel Energy Action Food Energy Regeneration Reproduction arbon hemistry
Biosynthetic Functions of the TA ycle Steroids PEP Pyruvate Fatty Acids Acetyl-oA Pyrimidine Bases Acetyl-oA (cytosol) Thr Asp xalaoacetate itrate Ile Met Asn Malate TA ycle Isocitrate Glutathione Lys Fumarate α-ketoglutarate Glu rnithine Succinyl-oA Pro Gln Arg Porphyrines Purine Bases eme hlorophyll Vitamin B 12 p. 46
Anabolic Function atabolic Function Glycolysis PEP Pyruvate 2 Acetyl-oA xalaoacetate itrate Malate TA ycle Isocitrate 2 Remove Intermediates Fumarate Succinyl-oA α-ketoglutarate 2
Anabolic Function atabolic Function Glycolysis PEP Pyruvate 2 Acetyl-oA xalaoacetate itrate Malate TA ycle Isocitrate 2 Remove Intermediates Fumarate Succinyl-oA α-ketoglutarate 2
Anabolic Function atabolic Function Glycolysis PEP Pyruvate 2 Anaplerotic Reactions 3 Acetyl-oA 2 2 xalaoacetate itrate Malate TA ycle Isocitrate 2 Remove Intermediates Fumarate Succinyl-oA α-ketoglutarate 2