Enzymes: Remarkable Biological

CatalystsJianing Li

Chemistry DepartmentColumbia 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 dete

rmine 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: ppHH, tempertemperatureature, concentrationconcentration of enzyme and substrate

Why highly efficient?

Catalytic power and specificity

Enzymes and Cofactors Most other enzymes are named for their s

ubstrates 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 enzymeFrom 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 e

tc.

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?a. Enzymes are usually classified on their

structures.b. Enzymes are usually classified on their

mechanismc. Enzymes are classified into 5 classesd. Enzymes are classified into 7 classesGo back

Question 1.2

Enzymes are sensitive to these following factors except:

a. pH valueb. Temperaturec. Concentration of enzyme and substrated. LightGo back

Question 1.3

The molecules which decrease the enzyme activity are called:

a. Activatorsb. Initiatorsc. Indicatorsd. InhibitorsGo back

Question 1.4

If we want to deactivate an enzyme, we do these except:

a. Increase the temperatureb. Add inhibitorsc. Remove the coenzymed. Add salt solutionGo back

Question 2.1

Which statement is not the character of enzyme?

a. High efficiencyb. Mild conditionc. Specificityd. Turnover the reactionGo back

Question 2.2

Enzymes don’t change quantitatively in the biochemical reactions, but they change in structures temporarily.

a. This statement is falseb. This statement is completely truec. This statement is only true partiallyGo back

Question 2.3

How do animals make light?a. They heat themselvesb. They eat special chemicals which can give off

lightc. They make light from an enzyme-catalyzed

reactiond. All are correctGo 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?

a. Increase the temperatureb. Increase the external pressurec. Add enzymesd. Add inhibitorsGo back

Question 3.1

There are __ kinds of inhibitor(s)?

a. 6

b. 5

c. 2

d. 1

Go back

Question 3.2

Cofactors aren’t:a. Enzymes

b. Metal ions

c. Small molecules

d. Vitamins

Go back

Question 3.3

Which of the following statement is correct?

a. Enzymes are specificb. The “lock-key” model shows that a enzyme is

flexible in structure and change itself to accommodate the substrate

c. Enzymes don’t change activation energyGo back

Question 3.4

Which statement is nor correct?a. All the enzymes are proteins

b. Not all the enzymes are proteins

c. Most enzymes are proteins

d. No enzyme is protein

Go back