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LEHNINGER PRINCIPLES OF BIOCHEMISTRY

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Presentation on theme: "LEHNINGER PRINCIPLES OF BIOCHEMISTRY"— Presentation transcript:

1 LEHNINGER PRINCIPLES OF BIOCHEMISTRY
David L. Nelson and Michael M. Cox LEHNINGER PRINCIPLES OF BIOCHEMISTRY Sixth Edition CHAPTER 6 Enzymes © 2013 W. H. Freeman and Company

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4 Name the reaction type and the coenzyme used

5 Binding of a substrate to an enzyme at the active site

6 There is an energy barrier between formation of product from substrate There is an activation energy for formation of the transition state

7 Enzymes enhance reaction rates by lowering activation energies Enzymes do not affect equilibrium

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11 How a catalyst circumvents unfavorable charge development during cleavage of an amide

12 Amino acids in general acid-base catalysis

13 Effect of substrate concentration on the initial velocity of an enzyme-catalyzed reaction
Michaelis-Menten plot Double-reciprocal or Lineweaver-Burk plot

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15 kcat = Vmax / [E]total kcat has units of reciprocal time

16 kcat / Km is a measure of catalytic efficiency

17 Many enzymes catalyze reactions with two or more substrates

18 Three types of reversible inhibition

19 Three types of reversible inhibition

20 Three types of reversible inhibition

21 Competitive inhibition
Uncompetitive inhibition Mixed inhibition

22 Molecules that are transition state analogs are effective reversible competitive inhibitors

23 Irreversible enzyme inhibition

24 pH – activity profiles for two enzymes

25 Structure of chymotrypsin, a serine protease

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34 Mechanism of action of HIV protease

35 HIV protease inhibitors

36 The transpeptidase reaction

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38 Mechanism of action of penicillin

39 Beta lactamase inactivates penicillin

40 Inactivation of beta lactamase by clavulanic acid

41 Subunit interactions in an allosteric enzyme, and interactions with inhibitors and activators

42 Aspartate transcarbamoylase, an allosteric enzyme

43 Regulation of enzyme activity by covalent modification

44 Regulation of enzyme activity by covalent modification

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46 Regulation of enzyme activity by proteolytic cleavage
Example: Activation of zymogens, inactive precursors of proteases

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