Enzymes

1. Enzymes Biochemistry

2. What You Need to Know! • Enzymes work by lowering the energy of activation. • The catalytic cycle of an enzyme that results in the production of a final product. • The factors that influence the efficiency of enzymes.

3. Special Proteins: Enzyme • Enzymes are proteins that speed up the rate of a chemical Rx • Making/breaking covalent bonds in cells • Also called a biological catalyst • Suffix: -ase Enzyme • Substrate(s)  product(s)

4. Enzymes are large 3-D proteins that have a groove where they bind the substrate(s)  active site

5. Enzyme • Each enzyme: • Has a specific 3-D structure (due to the number and order of AA) • Can interact only with one type of substrate that fits in the active site: Lock and Key model

6. Catalytic Cycle • Enzyme finds substrate • Substrate binds to active site “enzyme-substrate complex”

7. Enzyme Rx • Enzyme transforms the substrate into product “enzyme product complex” • Enzyme releases product • An enzyme can carry out a chemical Rx over and over again • it is not used up in the Rx • Substrates are used up

8. Activation Energy • Transformation from reactants to products requires the input of energy = activation energy • Enzymes can speed up a Rx because they lower the activation energy of the Rx

9. Enzyme Rx RatesDepend On: • Substrate concentrations • The more substrate, the faster the rate • Until present enzymes reach capacity • Enzyme concentrations • The more enzymes the faster the rate • Until substrate concentration becomes limiting factor • pH • Can slow the rate due to denaturation of enzyme

10. Enzyme Rx RatesDepend On: • Temperature • Can slow rate due to denaturation of enzyme • Presence of inhibitors • Can slow down or block enzymes

11. To be continued…

12. Factors that affect enzyme activity: • pH • Enzyme pepsin in stomach does not become active until it is in an acidic pH • Temperature • Each enzyme has an optimal temperature range • Cofactors or coenzymes • Bind to the enzyme to make it functional • Ex: metals such as Zn, Fe, Co, and vitamins • Inhibitors

13. 1. Competitive Inhibitor (reversible) • Mimics substrate molecule(s) (flat toothpicks) but cannot be metabolized • slows down Rx rate

14. 2. Non-competitive/allosteric inhibitors (reversible) • Molecules that do not bind to active site but at the allosteric (other) site • leading to conformation (change in shape) • Can turn off active site

15. Enzymes • http://www.youtube.com/watch?v=PILzvT3spCQ&feature=related

16. 3. Non-competitive inhibitors-(irreversible) • Toxins • Poisons

17. Enzyme Regulation • Chemical chaos would result if all metabolic pathways in the body work simultaneously Regulation through: • Transcription/translation • Active regulation of enzymes already made: • Allosteric Regulation • Feedback Inhibition

18. Active Regulation • Allosteric Regulation: • Reversible non-competitive inhibitors or activators that the body makes • binds to allosteric site • Feedback Inhibition: • In long metaboloic pathways final products becomes allosteric inhibitors to the first enzyme