Chapter 14 Biocatalysis Hour 4

7/30/2019 Chapter 14 Biocatalysis Hour 4

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Powerpoint@lecture Slides Are Prepared By Biology Lecturer, KMPk


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14.1: Properties of enzymesand mechanisms of

actions

. : o ac ors

14.3: Inhibition

14.4: Enzyme Classificationaccording to common

name and IUB


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TYPES OF INHIBITORS?

Reversible


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Allosteric means other site

Active site

E

Allosteric

site

2008 Paul Billiet ODWS

Inhibitor fits into

allostericallosteric sitesite

Substrate

cannot fit into

the active siteactive site


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The allosteric site the

enzyme on-off switch

E

Active

site

Allosteric

Substrate

Conformational

emptyfits into

the active

site

The inhibitor

molecule is

absentabsent

change

Inhibitor fits

into allostericallostericsitesite

Substrate

cannot fit

into the

active siteactive site

Inhibitor

molecule

is presentpresent

2008 Paul Billiet ODWS


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EXAMPLE NONCOMPETITIVE

INHIBITOR


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At the end of this topic, students should be able to:

1) Explain irreversible inhibition.

2) Describe enzyme classification according to IUB or

classes of reaction e.g. oxidoreductaseoxidoreductase, transferasetransferase,

hydrolasehydrolase, lyaselyase, isomerasesomerase and ligaseligase.


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Inhibitor permanentlypermanently bindbind or irreversiblyirreversibly to

activeactive sitesite of enzyme.

a oster ca oster c s tes te o enzyme.

Often form a covalentcovalent bondbond to an amino acid

residue at or near the active site.


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Permanently inactivateinactivate the enzyme.

Example:

Cyanide

Nerve gases and pesticide

IRREVERSIBLE INHIBITORS

www.themegallery.com


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EXAMPLE OF IRREVERSIBLE

INHIBITORS

Cyanide irreversibly inhibits activity of

cytochrome oxidase (in cellular respiration).

Blocks transfer of electrons from

substrate to O2 & death may occur.

www.themegallery.com


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A systematic nomenclature for enzymes was

recommended by the International Union ofthe International Union of

Biochemistry (IUB)Biochemistry (IUB).

THE CLASSIFICATION OF

ENZYMES

Each enzymes was allocated a trivial name:

The name of the substrate act upon the enzyme

The type of reaction catalysed

The suffix ase E.g: urase, sucrase, protease.


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Enzyme group Type of reactioncatalyzed

Enzymeexamples


ENZYMES

www.themegallery.c

. x ore uc ase rans er oand H atomsbetweensubstances.

All oxidation-

reductionreactions.

e y rogenase

Oxidase

Catalase


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Enzyme Group Type of reactioncatalyzed

Enzymeexamples


ENZYMES

www.themegallery.c

2. Transferase Transfer of afunctional groupfrom onesubstance toanother

Transaminase

Phosphorylase

Kinase


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Enzymeexamples


ENZYMES

www.themegallery.c

3. Hydrolase Hydrolysisreactions

Peptidase

Lipase

Amylase


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Enzymeexamples


ENZYMES

www.themegallery.c

4. Lyases Addition orremoval of afunctional group

without additionof water

Pyruvatedecarboxylase


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Enzymeexamples


ENZYMES

www.themegallery.c

5. Isomerase Catalyse geometricor structuralrearrangementwithin one molecule

Phosphoglucomutase

Mutase

Isomerase


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Enzymeexamples


ENZYMES

www.themegallery.c

6. Ligase Formation ofbonds betweentwo moleculesusing energy

derived from thebreakdown ofATP

Synthetase

DNA ligase

wahida@ernyjuliaMac2009


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QUESTION 1

We can describe inhibition as irreversible when

.B. we can reverse it by adding more substrate

C. covalent bonds form between the inhibitor and the

enzyme

D. hydrogen bonds form between the inhibitor and theenzyme


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QUESTION 2

How can you describe an inhibitor that does Not bind

to the active site but the other parts of the enzyme?

A. a reversible inhibitor

B. a competitive inhibitor

C. an irreversible inhibitor

D. a non-competitive inhibitor


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Chapter 14 Biocatalysis Hour 4