Enzymes: Remarkable Biological Catalysts

1. Enzymes: Remarkable Biological Catalysts Jianing Li Chemistry Department Columbia University April 14th,2007

2. The activity of an enzyme is responsible for the glow of the luminescent jellyfish

3. Basic Concepts • Enzyme • Substrate • Active Site • Cofactor and coenzyme • Inhibitor

4. What is an enzyme? • The catalyst of biological systems • The remarkable molecular device that determine the patterns of chemical reactions • Catalytic power and specificity • Mainly proteins, but ribozyme (RNA)

5. What are the characteristics of enzymes? • Higher efficiency • Milder conditions • Greater reaction specificity • Capacity for regulation Factors influencing enzyme activity: pH, temperature, concentration of enzyme and substrate

6. Why highly efficient?

7. Catalytic power and specificity

8. Enzymes and Cofactors • Most other enzymes are named for their substrates and for the reactions that they catalyze, with the suffix "ase" added. (ATPase ) • Many enzymes require cofactors for activity • Cofactors are small molecules or metal ions • Vitamins

9. Cofactor in an enzymeFrom www.psc.edu

11. Six major classes of enzymes • Oxidoreductases • Transferases • Hydrolases • Lyases • Isomerases • Ligases

12. Active Sides

13. How does an Enzyme Work?

14. Lock-and–Key Model

15. Induce-Fit Model

16. Inhibitors

17. If you want to know more about enzymes: • http://www.northland.cc.mn.us/biology1111/animations/enzyme.swf • http://ca.expasy.org/spdbv/text/getpc.com • http://biochem.ucl.ac.uk/bsm/enzymes/ • Biochemistry, 5th edition, Jeremy M. Berg etc.

20. Exercise: • Surf in an enzyme data base • Find an example for each class of enzyme • Think about the PDB ID, Name, Class, Reaction, Cofactor

21. Let’s play a game

22. Question 1.1 • Which statement is correct about enzyme classification? • Enzymes are usually classified on their structures. • Enzymes are usually classified on their mechanism • Enzymes are classified into 5 classes • Enzymes are classified into 7 classes Go back

23. Question 1.2 • Enzymes are sensitive to these following factors except: • pH value • Temperature • Concentration of enzyme and substrate • Light Go back

24. Question 1.3 • The molecules which decrease the enzyme activity are called: • Activators • Initiators • Indicators • Inhibitors Go back

25. Question 1.4 • If we want to deactivate an enzyme, we do these except: • Increase the temperature • Add inhibitors • Remove the coenzyme • Add salt solution Go back

26. Question 2.1 • Which statement is not the character of enzyme? • High efficiency • Mild condition • Specificity • Turnover the reaction Go back

27. Question 2.2 • Enzymes don’t change quantitatively in the biochemical reactions, but they change in structures temporarily. • This statement is false • This statement is completely true • This statement is only true partially Go back

28. Question 2.3 • How do animals make light? • They heat themselves • They eat special chemicals which can give off light • They make light from an enzyme-catalyzed reaction • All are correct Go back

29. Question 2.4 • If you are going to do an experiment, but it is very slow at room temperature. Which way can speed it up most? • Increase the temperature • Increase the external pressure • Add enzymes • Add inhibitors Go back

30. Question 3.1 • There are __ kinds of inhibitor(s)? • 6 • 5 • 2 • 1 Go back

31. Question 3.2 • Cofactors aren’t: • Enzymes • Metal ions • Small molecules • Vitamins Go back

32. Question 3.3 • Which of the following statement is correct? • Enzymes are specific • The “lock-key” model shows that a enzyme is flexible in structure and change itself to accommodate the substrate • Enzymes don’t change activation energy Go back

33. Question 3.4 • Which statement is nor correct? • All the enzymes are proteins • Not all the enzymes are proteins • Most enzymes are proteins • No enzyme is protein Go back