1. Enzyme Action Learning objective: to describe different models for enzyme action and to investigate factors which control the rate of an enzyme reaction 18 th October

2. Lock and Key

3. However certain substances can bind to the enzyme at sites other than the Active site and modify its activity (inhibitors/co-factors) Idea that the enzyme is flexible

4. Induced Fit

5. Enzyme reactions enzyme + substrateenzyme-substrate complex

6. Enzyme reactions enzyme + substrateenzyme-substrate complex E +S ES

7. Enzyme reactions enzyme + product enzyme-substrate complex E +PES enzyme + substrateenzyme-substrate complex E +S ES

8. Enzyme activity How fast an enzyme is working Rate of Reaction

9. Enzyme activity How fast an enzyme is working Rate of Reaction Rate of Reaction = Amount of substrate changed (or amount product formed) in a given period of time.

10. Rate of Reaction Enzyme activity Variable you are looking at

11. Enzyme activity Four Variables

12. Enzyme activity Four Variables Temperature pH Enzyme Concentration Substrate Concentration

13. Rate of Reaction Temperature

14. Rate of Reaction Temperature 0203050104060

15. Rate of Reaction Temperature 0203050104060 40 o C - denatures 5- 40 o C Increase in Activity <5 o C - inactive

16. Effect of heat on enzyme activty If you heat the protein above its optimal temperature bonds break meaning the protein loses it secondary and tertiary structure

17. Effect of heat on enzyme activty Denaturing the protein

18. Effect of heat on enzyme activty Denaturing the protein ACTIVE SITE CHANGES SHAPE SO SUBSTRATE NO LONGER FITS Even if temperature lowered – enzyme can’t regain its correct shape

19. Rate of Reaction pH

20. Rate of Reaction pH 1 342 5 6 789

21. Rate of Reaction pH 1 342 5 6 789 Narrow pH optima

22. Rate of Reaction pH 1 342 5 6 789 Narrow pH optima WHY?

23. Rate of Reaction pH 1 342 5 6 789 Narrow pH optima Disrupt Ionic bonds - Structure Effect charged residues at active site

24. Rate of Reaction Enzyme Concentration

25. Rate of Reaction Enzyme Concentration

26. Rate of Reaction Substrate Concentration

27. Rate of Reaction Substrate Concentration

28. Rate of Reaction Substrate Concentration Active sites full- maximum turnover

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