Download - 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
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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.
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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
THE CLASSIFICATION OF
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
THE CLASSIFICATION OF
ENZYMES
www.themegallery.c
2. Transferase Transfer of afunctional groupfrom onesubstance toanother
Transaminase
Phosphorylase
Kinase
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Enzyme Group Type of reactioncatalyzed
Enzymeexamples
THE CLASSIFICATION OF
ENZYMES
www.themegallery.c
3. Hydrolase Hydrolysisreactions
Peptidase
Lipase
Amylase
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Enzyme Group Type of reactioncatalyzed
Enzymeexamples
THE CLASSIFICATION OF
ENZYMES
www.themegallery.c
4. Lyases Addition orremoval of afunctional group
without additionof water
Pyruvatedecarboxylase
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Enzyme Group Type of reactioncatalyzed
Enzymeexamples
THE CLASSIFICATION OF
ENZYMES
www.themegallery.c
5. Isomerase Catalyse geometricor structuralrearrangementwithin one molecule
Phosphoglucomutase
Mutase
Isomerase
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Enzyme Group Type of reactioncatalyzed
Enzymeexamples
THE CLASSIFICATION OF
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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.