1. Chapter 7 Chem 341 Suroviec Fall 2013

2. I. Introduction The structure and mechanism can reveal quite a bit about an enzyme’s function

3. A. Reaction Kinetics S  P Progress of this reaction can be expressed as a velocity

4. A. Reaction Kinetics When enzyme concentration is help constant the reaction velocity will vary with [A]

5. II. Michaelis – Menton Eqn. A.Rate equations describe chemical processes Unimolecular reactions Bimolecular reactions

6. B. Michaelis Menton Equation is rate equation Simplest cases enzyme binds to substrate before converting to product The reaction of E + P converting back to ES is a step that we assume does NOT happen.

7. B. Michaelis Menton Equation We can measure by choosing the experimental conditions We then further choose experimental conditions to simplify the calculations: STEADY STATE

8. C. Michaelis Constant (K m ) and Initial Velocity ( ) and Maximal Velocity (V max )

9. Occurs a high substrate concentration when enzyme is saturated At substrate concentration at which [S] = K M So if enzyme has small K m achieves max catalytic efficiency at low [S] K M is unique for each enzyme- substrate pair C. Michaelis Constant (K m ) and Initial Velocity ( ) and Maximal Velocity (V max )

10. Michaelis Constant is a combination of 3 rate constants that is experimentally determined. C. Michaelis Constant (K m ) and Initial Velocity ( ) and Maximal Velocity (V max )

11. D. k cat catalytic constant = turnover # How fast an enzyme operates after it has selected and bound its substrate. Number of catalytic cycles that each active site undergoes per unit time

12. E. k cat /K M = measure of efficiency Enzyme effectiveness depends on ability to bind substrates and rapidly convert

13. F. Analysis: Find V max, K M High values of [S] lead to v o asymptotically reaching V max Use linear plot –Lineweaver-Burk

14. G. Exceptions to M-M Model 1. Multi-substrate reaction

15. G. Exceptions to M-M Model 2. Multi-step reactions 3. Non-hyperbolic reaction

16. II. Inhibition Substance that reduces an enzyme’s activity by influencing –Binding of substrate –Turnover number Variety of mechanisms –Irreversible enzyme inhibitors Inactivators –Reversible Diminish enzyme’s activity by interacting reversibly Structurally resemble substrates Affect catalytic activity without interfering with substrate binding A. Competitive Inhibition Compete directly with normal substrate for binding site Resemble substrate Specifically binds to active site Product inhibition

17. A. Competitive Inhibition Transition state analogs Depends on inhibitor binding selectively with RAPID equilibrium

18. A. Competitive Inhibition M-M equation for competitive inhibition reaction

19. 1. K I can be measured

20. B. Transition State Inhibitors Inhibitor binds to ES complex Not to free enzyme

21. C. Mixed Inhibition Interact in a way with the enzyme that affects substrate binding

22. III. Allosteric Regulation Organism must be able to regulate catalytic activities –Metabolic processes –Respond to changes in environment 1.Control of enzyme availability Amount of given enzyme in a cell depends on its rate of synthesis and its rate of degradation 2.Control of enzyme activity Catalytic activity controlled through structural alteration Can cause large changes in enzymatic activity