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Enzymes

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What Are Enzymes?Most enzymes are

Proteins (tertiaryand quaternarystructures)

Act as Catalyst toaccelerate a reaction

Not permanentlychanged in the

process

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Enzymes

Are specific for

what they willcatalyzeAre Reusable

End in ase-Sucrase-Lactase

-Maltase

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Biological Role of Enzymes

Cheese Making

Fruit Juice Making Desizing Fabrics

Destaining fabrics

Dehairing hides

Recovering silver from photographic films Wound healing

Augmentingsurgery

Disolving Blood clot

ClinicaL Chemistry

Bioremediation

Bioprocessing

Biofermentor Production f Chemicals

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How do enzymes Work?

Enzymes work byweakening bondswhich lowers

activationenergy

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Enzymes

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FreeEnergy

Progress of the reaction

Reactants

Products

Free energy of activation

Without Enzyme

With Enzyme

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Enzyme-Substrate Complex

The substance

(reactant) anenzyme acts on

the substrate

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EnzymeSubstrate Joins

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Active Site

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A restricted region of an enzymemolecule which binds to thesubstrate.

Enzyme

Substrate

ActiveSite

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Mechanisms of Enzyme Action

Lock and Key Model- Emil Fisher

Induced Fit Model- Daniel Koshland

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I d d Fi

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Induced Fit

A change in the

shape of anenzymes active

siteInduced by thesubstrate

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Induced Fit

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A change in the configuration of an

enzymes active site (H+ and ionicbonds are involved).

Induced by the substrate.

Enzyme

Active Sitesubstrate

induced fit

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What Affects Enzyme Activity?

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Three factors:1. Environmental Conditions

2. Cofactors and Coenzymes

3. Enzyme Inhibitors

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1. Environmental Conditions

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1. Extreme Temperature are the mostdangerous

- high tempsmay denature (unfold)the enzyme.

2.pH (most like 6 - 8 pH nearneutral)

3.Ionic concentration (salt ions)

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2. Cofactors and Coenzymes

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Inorganic substances (zinc, iron) andvitamins (respectively) are sometimesneed for proper enzymatic activity.

Example:Iron must be present in the quaternary

structure - hemoglobin in order for itto pick up oxygen.

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Two examples of Enzyme Inhibitors

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a. Competitive inhibitors: arechemicals that resemble anenzymes normal substrate and

compete with it for the activesite.

EnzymeCompetitive inhibitor

Substrate

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Inhibitors

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b. Noncompetitive inhibitors:Inhibitors that do not enter the

active site, but bind toanother part

of the enzyme causing the enzymeto change its shape, which in turnalters the active site.

Enzymeactive site

altered

NoncompetitiveInhibitorSubstrate

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Regulation of Enzymes

Regulation of enzymaticpathways prevent thedeletion of substrate

Regulation happens atthe level of the enzyme ina pathway

Feedback inhibition iswhen the end productregulates the enzymeearly in the pathway

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Feedback Regulation

Negative feedback

pathway is inhibited byaccumulation of finalproduct

Positive feedback

aregulatory moleculestimulates the activity ofthe enzyme, usually

between 2 pathways ADP levels cause the

activation of the glycolysispathway to make more

ATP

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Allostery

Conformational coupling of 2 widelyseparated binding sites must be

responsible for regulation active site

recognizes substrate and 2nd site

recognizes the regulatory molecule

Protein regulated this way undergoes

allosteric transition or a conformational

change Protein regulated in this manner is an

allosteric protein

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Allosteric Regulation

Method of regulation is also used in otherproteins besides enzymes Receptors, structural and motor proteins

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Allosteric Regulation

Enzyme is only partially active with sugar only butmuch more active with sugar and ADP present

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Phosphorylation

Some proteins are regulated by the addition of aPO4 group that allows for the attraction of +charged side chains causing a conformation

change Reversible protein phosphorylations regulate

many eukaryotic cell functions turning things onand off

Protein kinases add the PO4

and proteinphosphatase remove them

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Phosphorylation/Dephosphorylation

Kinases capable ofputting the PO4 on 3different amino acidresidues Have a OH group on R

group Serine

Threonine

Tyrosine

Phosphatases thatremove the PO4 maybe specific for 1 or 2reactions or many benon-specific