Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place. Lecture 15

Today’s lecture Enzymes Michealis-Menten Kinetics Lineweaver-Burk Plot Enzyme Inhibition Competitive Uncompetitive 2

Last lecture 3

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Enzymes Michaelis-Menten Kinetics. Enzymes are protein like substances with catalytic properties. Enzyme unease. [From Biochemistry, 3/E by Stryer, copywrited 1988 by Lubert Stryer. Used with permission of W.H. Freeman and Company.] 5

Enzymes It provides a pathway for the substrate to proceed at a faster rate. The substrate, S, reacts to form a product P. A given enzyme can only catalyze only one reaction. Example, Urea is decomposed by the enzyme urease. Slow SP Fast 6

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A given enzyme can only catalyze only one reaction. Urea is decomposed by the enzyme urease, as shown below. 9

The corresponding mechanism is: 10

Michaelis-Menten Kinetics 11

Michaelis-Menten Kinetics 12

V max =k cat * E t Turnover Number: k cat Number of substrate molecules (moles) converted to product in a given time (s) on a single enzyme molecule (molecules/molecule/time) For the reaction 40,000,000 molecules of H 2 O 2 converted to product per second on a single enzyme molecule. 13 H 2 O 2 + E → H 2 O + O + E k cat

Summary 14

(Michaelis-Menten plot) V max -r s S 1/2 Solving: K M =S 1/2 therefore K M is the concentration at which the rate is half the maximum rate CSCS Michaelis-Menten Equation 15

Inverting yields Lineweaver-Burk Plot slope = K M /V max 1/V max 1/S 1/-r S 16

Types of Enzyme Inhibition Competitive Uncompetitive Non-competitive 17

18 Competitive Inhibition

1) Mechanisms: Competitive Inhibition 19

2) Rates: Competitive Inhibition 20

Competitive Inhibition 21

From before (no competition): Intercept does not change, slope increases as inhibitor concentration increases Competitive Inhibition No Inhibition Competitive Increasing C I 22 Competitive

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Uncompetitive Inhibition Inhibition only has affinity for enzyme-substrate complex Developing the rate law (1) (2) 24

Adding (1) and (2) From (2) 25

Total enzyme 26

Slope remains the same but intercept changes as inhibitor concentration is increased Lineweaver-Burk Plot for uncompetitive inhibition 27

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Both slope and intercept changes Increasing I No Inhibition E + S E·S P + E (inactive)I.E + S I.E.S (inactive) +I -I Noncompetitive Inhibition (Mixed) 29

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End of Lecture 15 31