Presentation on theme: "Glycolysis: Energy Generation Without an Oxygen Requirement"— Presentation transcript:
1 Glycolysis: Energy Generation Without an Oxygen Requirement Glucose Biofuel Prominence:Low-reactive ring-form minimizes protein glycosylation
2 Glycolysis: A Three Step Process Glucose trapping and destabilization (priming)Three carbon unit generation (cleaving)Energy generation
3 Induced Fit in Hexokinase Glucose induces a large enzyme conformational changeSubstrate-induced cleftclosing prevents ATP hydrolysisKinases require a divalent metal ionWhat function does Mg+2 play in hexokinase?
4 Hexokinase Closed Around Substrates What mechanisms of catalysis are operative?
5 Hexokinase Reaction Mechanism What is the Nu:, electrophile, and leaving group in this reaction?
6 Phosphoglucose Isomerase: Aldose to Ketose Conversion
10 Base catalyzes ring closure Phosphoglucose Isomerase (PGI) G6P Conversion via Acid-Base CatalysisBase catalyzes ring closureH+
11 Phosphofructokinase: Trapping the Fructose Isomer What is the mechanism for this reaction?
12 Glycolysis Stage I: Glucose Trapping and Destabilization (priming)
13 Six Carbon Sugar Cleaved to Two Three Carbon Units What is the bond to be cleaved?Which alcohol becomes an aldehyde?
14 Haworth and Fischer Projections EquivalencyThe functional group that is down in a Haworth projection is positioned how in a Fischer structure?
15 Aldolase Reaction Mechanism Fructose-1,6-bisphosphate binds to the aldolase enzyme for covalent catalysis
16 Aldolase Reaction Mechanism What is lost when the Schiff base forms?
17 Aldolase Rxn Mechanism Aldolase Reaction MechanismAldolase Rxn MechanismCompare and contrast a Schiff base with a carbonyl group.
18 Aldolase Reaction Mechanism What is the process for Schiff base to carbonyl conversion?
19 Aldolase Reaction Mechanism H2OAldolase cleaves FBP into GAP and DHAP
20 Triose Phosphate Isomerase (TIM) Reversible and driven towards GAP due to product depletionWhich previous glycolytic step is similar to TIM?
21 Glycolysis: Step #5 Triose Phosphate Isomerase Triose Phosphate Isomerase Reaction MechanismGlycolysis: Step #5 Triose Phosphate IsomeraseTIM- or α,β-barrel with 8 parallel β-strands surrounded by 8 α-helices.DHAP conversion to GAP necessary to proceed through glycolysis
22 Stoichiometry: Stages 1-2 of Glycolysis Two ATPs are initially invested.One glucose is metabolized into two GAP molecules.
30 Pyruvate KinaseWhat is the Nu:, electrophile and leaving group for this reaction? (hint: consider phosphoglycerate kinase)
31 Glycolysis Energetic ∆G°ʹ ∆G Enzyme (kcal/mol) (kcal/mol) 1near equilibrium means that ∆G is about zeroWhat is the relationship between ∆G and ∆G°ʹ?When can ∆G and ∆G°ʹ diverge?
32 Regulating Glycolysis: A Pictorial Analogue Water representsmetabolite fluxWater amount inflask representsintermediateabundanceFlasks connectionsare enzymesVertical drop representsdecrease in free energyΔG° = height difference between flask bottomsΔG = height difference between water levels
33 Metabolic RegulationIrreversible reactions are potential regulatory sites (e.g. hexokinase, phosphofructokinase and pyruvate kinase)What duel role does ATP play in PFK-1 catalysis?In what direction does ATP regulate phosphofructokinase?
34 Energy Status Regulates Glycolytic Flow Elevated [ATP] sufficient energy; elevate [AMP] low energyADP + ADP ↔ ATP + AMP <adenylate kinase>Muscle Tissue
35 Fructose-2,6-Bisphosphate an Allosteric Regulator of Phosphofructokinase-1 PFK-2Liver TissueFront activation by fructose-6PF-2,6-BP amplifies or diminishes PFK-1 activity?
36 Fructose-2,6-Bisphosphate Reduces ATP Inhibition of Phosphofructokinase-1 PFK-2Liver TissueATP is a substrate and inhibitor of PFK-1
37 Fructose Entry Points for Glycolysis Glycerol-3PGlucose + FructoseMajor dietary sugars: sucrose (table sugar) and fructose (high-fructose corn syrup)