Glycolysis Anaerobic degradation of glucose to yield lactate or ethanol and CO 2

  • View
    222

  • Download
    0

Embed Size (px)

Text of Glycolysis Anaerobic degradation of glucose to yield lactate or ethanol and CO 2

  • GlycolysisAnaerobic degradation of glucose to yield lactate or ethanol and CO2

  • Learning ObjectivesSequence of ReactionsMetabolitesEnzymesEnzyme MechanismsEnergeticsRegulation

  • Overview of GlycolysisGlucose (C6) > 2 Pyruvate (C3)

    2 ADP + 2 Pi > 2 ATP

  • Figure 15-1Glycolysis

  • Stage I of Glycolysis(Energy Investment)2X

  • Summary of Stage IGlucose + 2 ATP > 2 GA3P + 2 ADP + 2 H+

  • Stage II of Glycolysis(Energy Recovery)Substrate Level PhosphorylationSubstrate Level Phosphorylation> Serine, Cysteine and Glycine

    > Aromatic Amino Acids

    > Alanine

  • Summary of Stage II2 GA3P + 2 NAD+ + 4 ADP + 2 Pi2 Pyruvate + 2 NADH + 2 H+ + 4 ATP

  • Summary of GlycolysisGlucose + 2 NAD+ + 2 ADP + 2 Pi2 Pyruvate + 2 NADH + 2 H+ + 2 ATPNOTE: NAD+ must be regenerated!

  • Reactions of Glycolysis

    Stage I

  • Hexokinase(First Use of ATP)NOTE: Lack of Specificity Go (kJ/mol) G (kJ/mol) Glucose + Pi G-6-P + H2O 13.8 20.5ATP + H2O ADP + Pi -30.5 -54.4Glucose + ATP G-6-P + ADP -16.7 -33.9

  • Page 489Role of Mg2+

  • Figure 15-2Substrate-induced Conformational Changes in Yeast Hexokinase

  • Results of Conformational ChangeFormation of ATP binding siteExclusion of waterIncreased nucleophilicity of CH2OHProximity effect

  • Regulation of HexokinaseInhibition by glucose-6-PImpermeability

  • Hexokinase versus GlucokinaseHexokinase (all tissues)Non-specificKM = ~100 MInhibited by glucose-6-PGlucokinase (primarily in liver)SpecificKM = ~10 mMNot inhibited by glucose-6-P

  • Functional RationaleMost tissues: metabolize blood glucose which enters cellsGlc-6-P impermeable to cell membraneProduct inhibitionLiver: maintain blood glucoseHigh blood glucose: glycogenLow blood glucose: glycolysis

  • Figure 22-4Hexokinase versus Glucokinase

  • Metabolism of Glucose-6-PRegulation!

  • Phosphoglucose Isomerase Go (kJ/mol) G (kJ/mol) Glucose-6-phosphate Fructose-6-phosphate 2.2 -1.4

  • Reaction Mechanism of Phosphoglucose Isomerase

  • Figure 15-3 part 1Reaction Mechanism of Phosphoglucose Isomerase(Substrate Binding)

  • Figure 15-3 part 2Reaction Mechanism of Phosphoglucose Isomerase(Acid-Catalyzed Ring Opening)

  • Figure 15-3 part 3Reaction Mechanism of Phosphoglucose Isomerase(Formation of cis-enediolate Intermediate)

  • Figure 15-3 part 4Reaction Mechanism of Phosphoglucose Isomerase(Proton Transfer)

  • Figure 15-3 part 5Reaction Mechanism of Phosphoglucose Isomerase(Base-Catalyzed Ring Closure)

  • Figure 15-3 part 1Reaction Mechanism of Phosphoglucose Isomerase(Product Release)

  • Phosphofructokinase(Second Use of ATP)NOTE: bisphosphate versus diphosphate Go (kJ/mol) G (kJ/mol) F-6-P + Pi F-1,6-bisP + H2O 16.3 36.0ATP + H2O ADP + Pi -30.5 -54.4F-6-P + ATP F-1,6-bisP + ADP -14.2 -18.8

  • Characteristics of Reaction Catalyzed by PFKRate-determining reactionReversed by Fructose-1,6-bisphosphataseMechanism similar to Hexokinase

  • Regulatory Properties of PFKMain control point in glycolysisAllosteric enzymePositive effectorsAMPFructose-2,6-bisphosphateNegative effectorsATPCitrate

  • Page 558-D-Fructose-2,6-Bisphosphate

  • Formation and Degradation of -D-Fructose-2,6-bisPHigh glucoseLow glucose

  • Aldolase456123Carbon #from glucose Go (kJ/mol) G (kJ/mol) F-1,6-bisP GAP + DHAP 23.8 ~0

  • Figure 15-4Mechanism of Base-Catalyzed Aldol CleavageNOTE: requirement for C=O at C2Rationale for Phosphoglucose Isomerase

  • Enzymatic Mechanism of Aldolase

  • Figure 15-5 part 1Enzymatic Mechanism of Aldolase(Substrate Binding)

  • Figure 15-5 part 2Enzymatic Mechanism of Aldolase(Schiff Base (imine) Formation)

  • Figure 15-5 part 3Enzymatic Mechanism of Aldolase(Aldol Cleavage)

  • Figure 15-5 part 4Enzymatic Mechanism of Aldolase(Tautomerization and Protonation)

  • Figure 15-5 part 5Enzymatic Mechanism of Aldolase(Schiff Base Hydrolysis and Product Release)

  • Triose Phosphate Isomerase Go (kJ/mol) G (kJ/mol) DHAP GAP 7.5 ~0

  • Part 494Enzymatic Mechanism ofTriose Phosphate Isomerase

  • Part 494Transition State Analog Inhibitors ofTriose Phosphate Isomerase

  • Figure 15-7Schematic Diagram of the First Stage of Glycolysis

  • Summary of Stage IGlucose + 2 ATP > 2 GA3P + 2 ADP + 2 H+

  • Reactions of Glycolysis

    Stage II

  • Glyceraldehyde-3-P DehydrogenaseGAPDH3,42,51,6 Go (kJ/mol) G (kJ/mol) GAP + NAD+ H2O 3-PG + NADH + H+ -43.1 36.03PG + Pi 1,3-BPG + H2O 49.4 -54.4GAP + NAD+ + Pi 1,3-BPG + NADH + H+ 6.3 -18.8

  • Acylphosphate

  • Enzymatic Mechanism ofGlyceraldehyde-3-P Dehydrogenase

  • Figure 15-9 part 1Enzymatic Mechanism ofGlyceraldehyde-3-P Dehydrogenase(Substrate Binding)

  • Figure 15-9 part 2Enzymatic Mechanism ofGlyceraldehyde-3-P Dehydrogenase(Thiol Addition)

  • Figure 15-9 part 3Enzymatic Mechanism ofGlyceraldehyde-3-P Dehydrogenase(Dehydrogenation)

  • Figure 15-9 part 4Enzymatic Mechanism ofGlyceraldehyde-3-P Dehydrogenase(Phosphate Binding)

  • Figure 15-9 part 5Enzymatic Mechanism ofGlyceraldehyde-3-P Dehydrogenase(Product Release)

  • 2,3-bisphosphoglycerate

  • Glycolysis deficiencies affect oxygen delivery

  • Phosphoglycerate KinaseFormation of first ATPsSubstrate-level Phosphorylation

  • Figure 15-10Yeast Phosphoglycerate Kinase

  • Coupled ReactionsG = ~0

  • Substrate Channeling

  • Phosphoglycerate Mutase Go (kJ/mol) G (kJ/mol) 3-PGA 2-PGA 4.4 ~0

  • Page 500Phosphohistidine Residue inPhosphoglycerate Mutase

  • Enzymatic Mechanism ofPhosphoglycerate Mutase

  • Figure 15-12 part 1Enzymatic Mechanism ofPhosphoglycerate Mutase(Substrate Binding)

  • Figure 15-12 part 2Enzymatic Mechanism ofPhosphoglycerate Mutase(Phosphorylation of Substrate)

  • Figure 15-12 part 3Enzymatic Mechanism ofPhosphoglycerate Mutase(Phosphorylation of Enzyme)

  • Figure 15-12 part 4Enzymatic Mechanism ofPhosphoglycerate Mutase(Product Release)

  • EnolaseFormation of high energy intermediateInhibition by F Go (kJ/mol) G (kJ/mol) 2-PGA PEP -3.2 -2.4

  • Pyruvate KinaseFormation of second ATPsSubstrate-level Phosphorylation Go (kJ/mol) G (kJ/mol) PEP + H2O Pyruvate + Pi -61.9 ADP + Pi ATP + H2O 30.5 PEP + ADP Pyruvate + ATP -31.4 -16.7

  • Figure 15-13Enzymatic Mechanism of Pyruvate Kinase

  • Figure 15-14Hydrolysis of PEP

  • Regulatory Properties ofPyruvate KinaseSecondary control point in glycolysisAllosteric enzymePositive effectorsADPFructose-1,6-bisphosphateNegative effectorsATP (energy charge)Acetyl-Coenzyme A

  • Figure 15-15Summary of Second Stage of Glycolysis

  • Summary of Stage II2 GA3P + 2 NAD+ + 4 ADP + 2 Pi2 Pyruvate + 2 NADH + 2 H+ + 4 ATP

  • Summary of GlycolysisGlucose + 2 NAD+ + 2 ADP + 2 Pi2 Pyruvate + 2 NADH + 2 H+ + 2 ATPNOTE: NAD+ must be regenerated!

  • Figure 15-16Metabolic Fates of Pyruvate

  • Recycling of NADHAnaerobic Fate of Pyruvate

  • Role of Anaerobic Glycolysis in Skeletal Muscle

  • Homolactate Fermentation

  • Page 505Lactate Dehydrogenase

  • MechanismofLactateDehydrogenase

  • Summary of Anaerobic GlycolysisGlucose + 2 ADP + 2 Pi2 Lactate + 2 ATP + 2 H2O + 2 H+

  • Energetics of FermentationGlucose > 2 LactateGlucose + 6 O2 > 6 CO2 + 6 H2OGo = -200 kJ/molGo = -2866 kJ/molMost of the energy of glucose is still available following glycolysis!

  • Alcoholic Fermentation

  • Figure 15-18Alcoholic Fermentation

  • Figure 15-18 part 1Pyruvate Decarboxylase

  • Page 507Thiamin PyrophosphateThiamine = Vitamin B1

  • Figure 15-20Mechanism ofPyruvate Decarboxylase

  • Figure 15-20 part 1Mechanism ofPyruvate Decarboxylase(Nucleophilic Attack)

  • Figure 15-20 part 2Mechanism ofPyruvate Decarboxylase(CO2 Elimination)

  • Figure 15-20 part 3Mechanism ofPyruvate Decarboxylase(Protonation of Carbanion)

  • Figure 15-20 part 4Mechanism ofPyruvate Decarboxylase(Product Release)

  • Figure 15-18 part 2Alcohol Dehydrogenase

  • Page 509Mechanism ofAlcohol Dehydrogenase

  • Regulation of Glycolysisand Gluconeogenesis

  • Table 15-1Free Energy Changes of Glycolytic Reactions

  • Figure 15-21Diagram of Free Energy Changes in Glycolysis

  • Regulatory Properties of HexokinaseInhibition by glucose-6-P

  • Metabolism of Glucose-6-PRegulation!

  • Regulatory Properties ofPhosphofructokinaseMain control point in glycolysis

  • Figure 15-23Regulation of Phosphofructokinase

  • Regulatory Properties ofPyruvate

Recommended

View more >