2. 2
What Are Enzymes?What Are Enzymes?
• Most enzymes are
ProteinsProteins ((tertiary
and quaternary
structures)
• Act as CatalystCatalyst to
accelerates a
reaction
• Not permanentlyNot permanently
changed in the
process
3. 3
EnzymesEnzymes
• Are specific for
what they will
catalyzecatalyze
• Are ReusableReusable
• End in –asease
-Sucrase-Sucrase
-Lactase-Lactase
-Maltase-Maltase
4. 4
How do enzymes Work?How do enzymes Work?
Enzymes work by
weakeningweakening
bondsbonds whichwhich
lowerslowers
activationactivation
energyenergy
8. 8
Active SiteActive Site
• A restricted regionrestricted region of an enzymeenzyme
molecule which bindsbinds to the substratesubstrate.
Enzyme
Substrate
Active
Site
9. 9
Induced FitInduced Fit
• A change in the
shapeshape of an
enzyme’s active
site
• InducedInduced by the
substrate
10. 10
Induced FitInduced Fit
• A changechange in the configurationconfiguration of an
enzyme’s activeenzyme’s active sitesite (H+ and ionic
bonds are involved).
• InducedInduced by the substratesubstrate..
Enzyme
Active Site
substrate
induced fit
11. 11
What Affects Enzyme Activity?What Affects Enzyme Activity?
• Three factors:Three factors:
1.1. Environmental ConditionsEnvironmental Conditions
2.2. Cofactors and CoenzymesCofactors and Coenzymes
3.3. Enzyme InhibitorsEnzyme Inhibitors
12. 12
1. Environmental Conditions1. Environmental Conditions
1. Extreme1. Extreme TemperatureTemperature are the mostare the most
dangerousdangerous
-- high tempshigh temps may denature (unfold)denature (unfold)
the enzyme.enzyme.
2.2. pHpH (most like 6 - 8 pH near(most like 6 - 8 pH near
neutral)neutral)
3.3. Ionic concentrationIonic concentration (salt ions)(salt ions)
13. 13
2. Cofactors and Coenzymes2. Cofactors and Coenzymes
• Inorganic substancesInorganic substances (zinc, iron)(zinc, iron) and
vitaminsvitamins (respectively) are sometimes need
for proper enzymatic activityenzymatic activity.
• Example:Example:
IronIron must be present in the quaternaryquaternary
structurestructure -- hemoglobinhemoglobin in order for it to pickpick
up oxygen.up oxygen.
14. 14
Two examples of EnzymeTwo examples of Enzyme
InhibitorsInhibitors
a.a. Competitive inhibitorsCompetitive inhibitors:: are
chemicals that resembleresemble an
enzyme’s normal substrateenzyme’s normal substrate and
competecompete with it for the activeactive
sitesite.
Enzyme
Competitive inhibitor
Substrate
15. 15
InhibitorsInhibitors
b.b. Noncompetitive inhibitorsNoncompetitive inhibitors::
Inhibitors that do not enter thedo not enter the
active siteactive site, but bind tobind to another partanother part
of the enzymeenzyme causing the enzymeenzyme to
change its shapechange its shape, which in turn
alters the active sitealters the active site.
Enzyme
active site
altered
Noncompetitive
Inhibitor
Substrate
