2. Lecture 2 August 3, 2005 Lehninger (4 th Edition), Chapter 6,

3. ENZYME KINETICS LNC Chapter 6

4. REACTANTS SUBSTRATES PRODUCTS k First order reactions:A  P k Second order reactions:A + B  P A + A  P

5. 1 st order:ln[A] = ln[A o ] - kt or [A] = [A o ] exp(-kt) 2 nd order: 1/[A] = 1/[Ao] + kt

6. TRANSITION STATE THEORY A C B D A C B D A C B D A catalyst serves in at least two ways: it binds and aligns the substrates it facilitates the redistribution of electrons (charges)

7. k 1 k 2 E + S ES Products k -1 CHAPTER 6 Enzymes and Enzyme Kinetics

8. Fig. 6-2

9. Fig. 6-3

10. Derivation of Michaelis-Menten equation 1. equilibrium assumption: k -1 >> k 2 2. steady state assumption:d[ES]/dt = 0 Note:[E] = [E] total – [ES]

11. Hmmm..??

12. when [S] >> K m then v  v max and v max = k 2 [E] T k 2 x [E] T x [S] v = ------------------------- K m + [S]

13. k -1 + k 2 K m = k 1

14. d K m K d when k -1 >> k 2

15. Fig. 6-11

16. Fig. 6-12

17. 1 K m 1 1 = x + v o v max [S] v max y = ax + b

18. Lineweaver-Burk Plot Double Reciprocal Plot box. 6-1

19. - another definition : v max k 2 = k cat = ------------ [E] T TURNOVER NUMBER

21. molecules of substrate / molecule of enzyme / second moles of substrate / mole of enzyme / second

22. Reactions with more than one substrate (more typical) Overall reaction: S 1 + S 2 P 1 + P 2

23. Fig. 6-13

24. LNC 6-14 a Lines intersect: ternary complex is formed in the reaction

25. LNC 6-13 b This case is also referred to as the Ping-Pong or double displacement mechanism

26. LNC 6-14 b Lines do not intersect: no ternary complex is formed

27. Enzyme Inhibitors

28. Fig. 6-15a

29. Competitive Inhibition  = 1 + [I] / K I box. 6-2.1

30. Fig. 6-15b

31. Uncompetitive Inhibition  ’ = 1 + [I] / K I box. 6-2.2

32. Fig. 6-15c

33. Mixed Inhibition When  =  ’, then we also speak of noncompetitive inhibition box 6-2.3

34. LNC 6-28 FEEDBACK INHIBITION

35. LNC 6-26

36. LNC 6-27 ASPARTATE TRANSCARBAMYLASE

37. LNC 6-29a

38. LNC 6-29b

39. LNC 6-29c

40. Part III Bioenergetics and Metabolism Chapter 13 in LNC

41. THE CARBON CYCLE

42. urea THE NITROGEN CYCLE

45. Types of Organic Reactions 1) Group transfer Glucose + ATP Glu-6-P + ADP H 2 O + ATP P i + ADP 2) Oxidation-reduction reactions Ethanol + NAH + acetaldehyde + NADH + H + 3) Eliminations, isomerizations, rearrangements aldose ketose 4) reactions involving making or breaking of C-C bonds Fru-1,6, bisphosphate dihydroxyacetone-phosphate + glyceraldehyde-3phosphate

46. End of Lecture 2 Aug. 3, 2005