Apple ExperimentApple Experiment

Come down and get an apple and a slice of lemon.

When you get back to your seat:1. Take a big bite of your delicious apple.2. Immediately squeeze lemon juice over the apple flesh that is now exposed from the bite.3. IMPORTANT! Don’t get lemon juice all over the apple. Make sure that it is ONLY on the area that you just bit!4. Set the lemon aside and wipe any lemon juice off of your hands with a napkin.5. Take another bite from the opposite side of your apple.6. Set your apple aside.

What Are Enzymes?What Are Enzymes?

Enzymes are __________ ((tertiary and quaternary structures).

An enzyme is a _________ in cellular reactions.

A catalyst accelerates a reaction.

EnzymesEnzymes

Are ________ for what they will catalyze

Are _________

Usually end in -_____-Sucrase-Sucrase-Lactase-Lactase-Maltase-Maltase

How do enzymes work?How do enzymes work?

Each enzyme has a unique 3-D shape, including a surface groove called an ______ _____.

The enzyme works by binding a specific chemical reactant (_________) to its active site, causing the substrate to become unstable and react.

The resulting __________ is then released from the active site.

How do enzymes work?How do enzymes work?

Enzymes work by _______ ______ which ________ activation energy.

Enzyme-Substrate ComplexEnzyme-Substrate ComplexThe reactant an

enzymeenzyme acts on is specifically called the _________.

EnzymeSubstrate Joins

______ ___________ _____A specific region of an enzymeenzyme molecule which

binds to the substratesubstrate.

EnzymeSubstrate

Active Site

Shape of a ProteinShape of a Protein

An enzyme fits with its substrate like a ____ and ____.

EnzymeAnimation : Gary E. Kaiser EnzymeAnimation : Gary E. Kaiser http://student.ccbcmd.edu/biotutorials/proteins/enzsub.htmlhttp://student.ccbcmd.edu/biotutorials/proteins/enzsub.html

View : View : http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.htmlanimation__how_enzymes_work.html

Enzymes are Enzymes are ____ ____________ ________ in the reactions they catalyze. in the reactions they catalyze.

Think of them as tiny machines in manufacturing. Think of them as tiny machines in manufacturing.

The more machines, the faster the accumulation of The more machines, the faster the accumulation of _________._________.

Image:

Wine Bottling : www.morrison-chs.com/timingscrews/index.html

Wine Vats: www.lymebaywinery.co.uk/pages/about_us.htm

Formats for writing a chemical Formats for writing a chemical reaction.reaction.

( ________ )

_______ + ________ -----------> _________

( ________ )

__________ -----------> ________ ________

4 levels of Protein Structure4 levels of Protein Structure

How Do You Stop How Do You Stop an Enzyme?an Enzyme?

Irreversible egg protein denaturation caused by high temperature (while cooking it).

_______________

• Alteration of a protein shape through some form of external stress

• Denatured protein can’t carry out its cellular function .

Factors Affecting Enzyme Factors Affecting Enzyme ActivityActivity

Temperature

pH

Cofactors & Coenzymes

Inhibitors

Temperature & pHTemperature & pH

Think about what kind of cell or organism an enzyme may work in…

Temperatures far above the normal range _________ enzymes

(This is why very high fevers are so dangerous. They can cook the (This is why very high fevers are so dangerous. They can cook the body’s proteins)body’s proteins)

Most enzymes work best near __________ pH (6 to 8).

Coenzymes & CofactorsCoenzymes & Cofactors Non-protein substances substances

(zinc, iron, copper, (zinc, iron, copper, vitamins) vitamins) are sometimes need for proper enzymatic activity.

• Coenzyme versus Cofactor: What’s the dif?

_________ more general term. Includes inorganic and organic molecules.

_________ type of Cofactor, But specifically organic molecules.

Image:

EnzymeCofactor : Public domain Wiki, Ribbon-diagram showing carbonic anhydrase II. The grey sphere is the zinc cofactor in the active site.

Coenzyme : Vitamin B12Coenzyme : Vitamin B12

ExampleExample::

Most _________ are coenzymes essential in helping move atoms between molecules in the formation of carbohydrates, fats, and proteins.

• Exclusively synthesized by ___________ (found primarily in meat, eggs and dairy products).

Image: VitaminB12 : NIH, Public Domain www.nlm.nih.gov/.../ency/imagepages/19516.htm

Two Types of Enzyme Two Types of Enzyme InhibitorsInhibitors

1.1. ___________ ____________:___________ ____________:

Chemicals that resembleresemble an enzyme’s enzyme’s normal substrate normal substrate and competecompete with it for the active siteactive site.

Enzyme

Competitive inhibitorSubstrate

1. Competitive inhibitors:1. Competitive inhibitors: Resembleesemble an enzyme’s normal substrate enzyme’s normal substrate and

competecompete with it for the active siteactive site.

Image: Competitive Inhibition : www-biol.paisley.ac.uk/.../chapter3_2.html

Two Types of Enzyme Two Types of Enzyme InhibitorsInhibitors

_______________ ______________:_______________ ______________:

Do not enter the active siteo not enter the active site, but bind to bind to another part another part of the enzymeenzyme causing the enzymeenzyme to change its shapechange its shape, altering the altering the

activeactive sitesite.

Enzyme

active site altered

NoncompetitiveInhibitor

Substrate

Enzyme InhibitorsEnzyme InhibitorsBlocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance.

Many _____ are enzyme inhibitors.

Enzyme inhibitors are also used as _________ and __________.

Images

Dead Bug : www.kansas.gov/help_center/user_testing.html

Prescription Drugs : www.patentdocs.us/.../08/by-kevin-e-noon.html

Regulation of Enzyme Regulation of Enzyme ActivityActivity

Enzyme activity is regulated by Enzyme activity is regulated by four different mechanisms*four different mechanisms*

(1) Allosteric control(2)Covalent modification

*changes in enzyme levels due to regulation of protein synthesis or degradation are additional, long-term ways to regulate enzyme activity

Allosteric regulation of enzyme Allosteric regulation of enzyme activityactivity(1) Allosteric regulation = the

activation or inhibition of an enzyme’s activity due to binding of an effector molecule at a regulatory site that is distinct from the active site of the enzyme

(2) Allosteric regulators generally act by increasing or decreasing the enzyme’s affinity for the substrate

Covalent modificationCovalent modification(1) Covalent modification allows an

enzyme to be rapidly activated or inactivated

(2) With covalent modification, regulation of a enzyme activity is achieved at low energy costs to the cell (i.e. regulation does not require synthesis of a new enzyme or inhibitory protein).

(3) Phosphorylation is a good example of how enzymes are activated and inactivated by covalent post-translational modifications

Covalent modification regulates the Covalent modification regulates the catalytic activity of some enzymescatalytic activity of some enzymes

Can either activate it or inhibit it by altering the conformation of the enzyme or by serving as a functional group in the active site.

Enzyme

Modifyinggroup

EnzymeModifyinggroup

Inactive Enzyme Active Enzyme

Summary of regulatory mechanismsSummary of regulatory mechanisms(1) Allosteric regulation

ATP activation/CTP inhibition of ATCase sigmoidal kineticscAMP activation of cAMP-dependent protein kinase

(2) Reversible covalent modificationPhosphorylation

Ser/Thr protein kinases, Tyr kinases, kinase cascades

CCC

Allosteric Enzyme ATCase

+

Active relaxed form

Inactive tense form

ATCase

RR

RR

RR

CCC

COO-

CH2

HN-C-COO-

H H-

---

OH2N-C-O-PO3

2-

= OH2N-C-

=

COO-

CH2

N-C-COO-

H H

---

-

Catalytic subunits

Catalytic subunits

Regulatory subunits

ATP

CTP

Nucleic acidmetabolism

Feedback inhibition

AspartateCarbamoylphosphate

Carbamoyl aspartate

CTP

CTP

CTP

CTP

CTP

CTP

Juang RH (2004) BCbasics

Quaternary structure

Sigmoidal Curve Effect Sigmoidal curve

Exaggeration of sigmoidal curveyields a drastic zigzag line that shows the On/Off point clearly

Positive effector (ATP)brings sigmoidal curveback to hyperbolic

Negative effector (CTP)keeps

Consequently, Allosteric enzyme can sense the concentration of the environment and adjust its activity

Noncooperative(Hyperbolic)

Cooperative(Sigmoidal)

CTPATP

vo

vo

[Substrate]Off On

Juang RH (2004) BCbasics

T

T

R

T

[S]

vo

Mechanism and Example of Allosteric Effect

S S

R

R

SS

RS

A

I

T[S]

vo

[S]

vo

(+)

(-) X X

X

R = Relax(active)

T = Tense(inactive)

Allosteric siteHomotropic(+)Concerted

Heterotropic(+)Sequential

Heterotropic(-)Concerted

Allosteric site

Kinetics CooperationModels

(-)

(+)

(+)

Juang RH (2004) BCbasics

Activity Regulation of Glycogen Phosphorylase

PA

PA

P

P

A

A

Covalent modificationCovalent modification

P

P

GP kinase

GP phosphatase 1

Non-covalent

Non-covalent

PA

PA

P

PPA

PAA

A

A

AMP

ATPGlc-6-PGlucoseCaffeine

GlucoseCaffeine

spontaneously

R

T

R

T

Ga

rre

tt &

Gris

ha

m (

19

99

) B

ioch

em

istr

y (2

e)

p.6

79