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

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

Basic Concepts Enzyme Substrate Active Site Cofactor and coenzyme Inhibitor

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)

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

Why highly efficient?

Catalytic power and specificity

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

Cofactor in an enzyme From www.psc.edu

Six major classes of enzymes Oxidoreductases Transferases Hydrolases Lyases Isomerases Ligases

Active Sides

How does an Enzyme Work?

Lock-and–Key Model

Induce-Fit Model

Inhibitors

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.

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

Let’s play a game Questions Number 1. Hard (20 credits each) (1.1) (1.2) (1.3) (1.4) 2. Medium (15 credits each) (2.1) (2.2) (2.3) (2.4) 3. Easy (10 credit each) (3.1) (3.2) (3.3) (3.4)

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

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

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

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

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

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

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

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

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

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

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

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