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Enzymes and Enzyme Kinetics I
Dr. Kevin Ahern
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Enzymatic Reactions
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Enzymatically Catalyzed Reactions
Substrates Enzymatically Catalyzed Reactions Background Enzyme Substrate(s) Active Site Active Site Substrates Bound at Active Site of the Methylene Tetrahydrofolate Reductase Enzyme
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Substrate Binding / Active Site
Lysozyme
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Enzymatic Reaction Substrate ‘A’ Substrate ‘B’ Enzyme
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Enzymatic Reaction Substrate ‘A’ Substrate ‘B’ Enzyme ES Complex
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Enzyme Changes Result in Reaction Between Substrates A and B
Enzymatic Reaction Enzyme Changes Result in Reaction Between Substrates A and B ES* Complex
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Substrates Affect Enzymes on Binding
Background ‘B’ Has Become ‘D’ ‘A’ Has Become ‘C’ Part of ‘A’ Has Moved to ‘B’ EP Complex
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Substrates Affect Enzymes on Binding
Background Product C Released Product D Released Enzyme Freed to Bind More Substrates E + P
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Free Enzyme & Substrates E + S ES Substrate Binding ES* Reaction EP
Steps In Catalysis Background Free Enzyme & Substrates E + S <=> ES Substrate Binding <=> Reversible ES* Reaction <=> EP Product Formation <=> E + P Release of Products
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A Serine Protease Binding Specificity Flexibility
Enzymes Mechanistics Binding Specificity Flexibility Electronic Environment Coenzymes A Serine Protease
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Substrate Binding
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Concerted Model of Catalysis
Enzymes Catalysis Considerations - Models Concerted Model of Catalysis
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Enzyme Action Activation Energy Necessary for Uncatalyzed Reaction
Free Energy of Substrate(s) Overall Free Energy Change Reaction Reverses Reaction Goes Forward Free Energy of Product(s)
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Enzyme Action Activation Energy Necessary for Uncatalyzed Reaction
Free Energy of Substrate(s) Activation Energy Necessary for Catalyzed Reaction No Overall Free Energy Change Reaction Reverses Reaction Goes Forward Free Energy of Product(s)
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Enzymes lower activation energy Enzymes catalyze reversible reactions
Enzymatic Reactions Enzymes lower activation energy Enzymes catalyze reversible reactions Enzymes do not change overall energy Enzymes do not change equilibrium concentrations Enzymes speed achieving equilibrium
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A <=> B At equilibrium, [A]T0 = [B]T0 [A]T0 = [A]T+5 Similarly,
Enzymatic Reactions A <=> B At equilibrium, [A]T0 = [A]T+5 Similarly, [B]T0 = [B]T+5 At any amount of time X after equilibrium has been reached, [A]T0 = [A]T+5 = [A]TX and [B]T0 = [B] T+5 = [B]TX However, unless ΔG°’ = 0, it is wrong to say [A]T0 = [B]T0
![A <=> B At equilibrium, [A]T0 = [B]T0 [A]T0 = [A]T+5 Similarly,](http://slideplayer.com/slide/13871284/85/images/17/A+%3C%3D%3E+B+At+equilibrium%2C+%5BA%5DT0+%3D+%5BB%5DT0+%5BA%5DT0+%3D+%5BA%5DT%2B5+Similarly%2C.jpg "Enzymatic Reactions. A <=> B. At equilibrium, [A]T0 = [A]T+5. Similarly, [B]T0 = [B]T+5. At any amount of time X after equilibrium has been reached, [A]T0 = [A]T+5 = [A]TX. and. [B]T0 = [B] T+5 = [B]TX. However, unless ΔG°’ = 0, it is wrong to say. [A]T0 = [B]T0.")
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Types of Reactions Substrate Binding
Single Substrate - Single Product : A ⇄ B Single Substrate - Multiple Products : A ⇄ B + C Multiple Substrates - Single Products : A + B ⇄ C Multiple Substrates - Multiple Products : A + B ⇄ C + D Ordered Random Ping-Pong
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Multiple Substrate Binding
Ordered Random Lactate Dehydrogenase NADH + Pyruvate Lactate + NAD+ Creatine + ATP Creatine phosphate + ADP Creatine Kinase No order to binding Must bind first
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Multiple Substrate Reactions - Double Displacement
Two things are happening
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Enzyme Flips Between Two States Enzyme Flips Between Two States
Enzymes Enzyme Flips Between Two States Ping-Pong Catalysis Enzyme Flips Between Two States
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E+S <=> ES <=> ES* <=> EP <=> E+P
Enzymes Kinetic Considerations Rate of Formation of Product of Primary Interest E+S <=> ES <=> ES* <=> EP <=> E+P If We Assume in the Simple Case that ES Proceeds Directly to E+P, where kf, kr, and kcat refer to the rate constants for formation of ES, reversible breakdown of ES, and conversion of ES to E+P, respectively
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The Way They Work Metabolic Melody Recording by David Simmons
(To the tune of "The Way We Were") Copyright © Kevin Ahern Enzymes Mighty powerhouse peptides Cause reactions to go faster In the cell’s insides Tiny substrates Bring about an induced fit Enzyme structure is affect-ed By what binds to it Can it be that it’s just simple zen? How the enzymes activate If they bind effector, will they go To an R-State, T-State? Folding Gives the mechanistic might To three-D arrangement Of the active site Have a bias they can’t hide Hydrophobic side chains are Mostly found inside So it’s the structure For celebrating Whenever there’s debating The way they work Metabolic Melody Recording by David Simmons & Liz Bacon Download HERE
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