1. Enzymes Biomolecules that catalyze chemical reactions - Increase reaction rates - Specific Oxidoreductases – catalyze redox reactions Transferases – transfer groups such as –CH 3 or -NH 2 Hydrolases – catalyze hydrolysis reactions Lyases – catalyze the removal or addition of double bonds Isomerases – catalyze isomerization reactions Ligases – catalyze the joining of two molecules

2. Terms Substrate - a compound that binds to the enzyme and is processed Active Site -region (pocket or cleft) in the enzyme where the substrate binds Activation - an increase in enzymatic activity (how well an enzyme works) Enzyme Activity -a measure of the rate of the reaction catalyzed by the enzyme Inhibition - a decrease in enzyme activity Inhibitor - a molecule that binds to the enzyme and inhibits activity

3. Mechanism of Enzyme Action Lock and Key Induced Fit - substrate binding induces conformational changes (structural changes) in the enzyme that promote catalysis

4. Lock and Key E + S

5. Lock and Key E + S  ES

6. Lock and Key E + S  ES  E + P

7. Induced Fit E + S

8. Induced Fit E + S 

9. Induced Fit E + S  ES

10. Induced Fit E + S  ES  E + P

11. Example: Hexokinase Hexokinase specifically binds both glucose and ATP Hexokinase speeds up the reaction

12. Glucose Binding

14. Hexokinase binds Glucose and ATP Substrate binding is governed by intermolecular forces

15. Example of Induced Fit

16. Citrate Synthase

17. Krebs Cycle

18. Citrate Synthase

23. Factors that effect enzyme activity Enzyme and Substrate Concentration Temperature pH Inhibitors E + S ⇌ ES → E + P

24. Competitive vs Noncompetitive Inhibition

25. Some Drugs are Enzyme Inhibitors Certain drugs bind to Enzymes and prevent binding of the normal substrates The enzyme is thus prevented from catalyzing a physiological reaction

26. HIV Drugs