1 Enzymes Enzymes By Muhammad Asif Pu Pak Muhammad Asif Pu
1
EnzymesEnzymesBy Muhammad AsifPu Pak
Muhammad Asif Pu
2
What Are Enzymes?What Are Enzymes?• Most enzymes
are Proteins Proteins ((tertiary and quaternary structures)
• Act as CatalystCatalyst to accelerates a reaction
• Not permanentlyNot permanently changed in the process
Muhammad Asif Pu
3
EnzymesEnzymes•Are specific
for what they will catalyzecatalyze
•Are ReusableReusable•End in –asease
-Sucrase-Sucrase-Lactase-Lactase-Maltase-Maltase
Muhammad Asif Pu
4
How do enzymes Work?How do enzymes Work?
Enzymes work by weakening weakening bondsbonds which which lowers lowers activation activation energyenergy
Muhammad Asif Pu
5
EnzymesEnzymes
FreeEnergy
Progress of the reaction
Reactants
Products
Free energy of activationFree energy of activation
Without Enzyme
With Enzyme
Muhammad Asif Pu
6Muhammad Asif Pu
7
Enzyme-Substrate ComplexEnzyme-Substrate ComplexThe substancesubstance
(reactant) an enzymeenzyme acts on is the substratesubstrate
EnzymeSubstrate Joins
Muhammad Asif Pu
8
Active SiteActive Site• A restricted regionrestricted region of an enzymeenzyme
molecule which bindsbinds to the substratesubstrate.
EnzymeSubstrate
Active Site
Muhammad Asif Pu
9
Induced FitInduced Fit•A change in the shapeshape of an enzyme’s active site
• Induced Induced by the substrate
Muhammad Asif Pu
10
Induced FitInduced Fit
• A changechange in the configurationconfiguration of an enzyme’s activeenzyme’s active site site (H+ and ionic bonds are involved).
• InducedInduced by the substratesubstrate..
Enzyme
Active Sitesubstrate
induced fit
Muhammad Asif Pu
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
Muhammad Asif Pu
12
1. Environmental Conditions1. Environmental Conditions
1. Extreme1. Extreme Temperature Temperature are the are the most dangerousmost dangerous
- - high tempshigh temps may denature denature (unfold) (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 (salt ions)ions)
Muhammad Asif Pu
13
2. Cofactors and Coenzymes2. Cofactors and Coenzymes
• Inorganic substances Inorganic substances (zinc, iron)(zinc, iron) and vitaminsvitamins (respectively) are sometimes need for proper enzymatic activityenzymatic activity.
• Example:Example:IronIron must be present in the
quaternary quaternary structurestructure -- hemoglobinhemoglobin in order for it to pick up oxygen.pick up oxygen.
Muhammad Asif Pu
14
Two examples of Enzyme Two 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 active active sitesite.
Enzyme
Competitive inhibitor
Substrate
Muhammad Asif Pu
15
InhibitorsInhibitors
b.b. Noncompetitive inhibitorsNoncompetitive inhibitors::Inhibitors that do not enter thedo not enter the
active siteactive site, but bind tobind to another another partpart of the enzymeenzyme causing the enzymeenzyme to change its shapechange its shape, which in turn alters the alters the active siteactive site.
Enzymeactive site altered
NoncompetitiveInhibitor
Substrate
Muhammad Asif Pu
16Muhammad Asif Pu