PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13MEDC 527 Fall 2008 1Enzyme ActionEnzymes … proteins with catalytic function… possess 1O, 2O, 3O and 4O structure… perform a variety of reactions e.g., hydrolysis, hydroxylation, oxidation, reduction, transfer of groups …… increase the rate of reaction (up to 1017-fold)MEDC 527 Fall 2008 2Enzyme ActionThree dimensional structure of an enzymeMEDC 527 Fall 2008 3Enzyme ActionCatalytic Triad Catalytic Triad Chymotrypsin Acetylcholine EsteraseMEDC 527 Fall 2008 4Chemical Mechanism of Enzyme ActionMEDC 527 Fall 2008 5Michaelis – Menten Kinetics and Enzyme Inhibition][][SKSVViMMAX][}][1{][SKIKSVViIMMAXMichaelis-Menten EquationMichaelis-Menten Equation in the presence of a competitive inhibitorWhat happens at low [S] in the absence of I?What happens at high [S] in the absence of I?What happens at low [S] in the presence of I?What happens at high [S] in the presence of I?MEDC 527 Fall 2008 6Reaction MechanismsTheory of Reaction RatesA + B C + DMEDC 527 Fall 2008 7Reaction MechanismsTheory of Reaction RatesH2C=CH2 + HCl H3C-CH2Cl H2C CH2HClH3C CH2+Cl-EnergyReaction Co-ordinateReactants(TS)#ProductsTransition StateEAGOMEDC 527 Fall 2008 8• [Conc. Of Reactants] (Z)• Temperature (T)• Activation Energy (EA)• Probability Factor (P) Reaction MechanismsCollision Theory• Arrhenius Equation … Rate = P×Z×e(–Ea/RT)Collision 1Collision 2Collision 3Collision 4MEDC 527 Fall 2008 9Reaction MechanismsTheory of Reaction Rates• Arrhenius Equation Rate = P×Z×e(–Ea/RT)NHCH3ONHCH2OHOOCNOOHOMeMeMeMeHpH 5, half–life = 300 yrspH 5, half–life = 25 dayspH 5, half–life = 25 minutesMEDC 527 Fall 2008 10NHOCH3NHOCH3C3H7NHOCH3HOOCRank the following molecules according to their ability to hydrolyze faster in water at pH 6.0. Use 1 for fastest and 3 for slowest rate of hydrolysis. Reaction MechanismsApplication of Reaction Rate TheoryMEDC 527 Fall 2008 11CH3CH3OOCH3COOHCH3OOCH3ClCH3OOCH3Rank the following molecules containing ester/amide group according to their ability to hydrolyze in water at pH 8.0. Use 1 for fastest rate and 3 for slowest rate of hydrolysis.Reaction MechanismsApplication of Reaction Rate TheoryMEDC 527 Fall 2008 12Reaction MechanismsTheory of Reaction RatesEnergyReaction Co-ordinateA + B(A…B)#C + DTransition StateActivated ComplexTransition Statein the presenceof an enzyme(A..B)#• Enzymes! … powerful catalystsCH3OOEtCH3OOCHOOEtNOHH AcCHOONOHH Ac85 yrs0.01 s__Another example, catalase: 2H2O2 2H2O + O2EA ~ 18 kcal/mol in absence; ~2 kcal/mol in presence; rate increase of ~1011 -foldMEDC 527 Fall 2008 13Reaction MechanismsReaction RatesOCH2CH3OOHOHOCH3CH3CH3CH3OCH2CH3Ot1/2H2O/OH-, pH 12.0t1/2A)B)H2O/OH-, pH 12.0Consider reactions A) and B). Circle the reaction that has a longer
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