biocatalysis 1
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15.1 PROPERTIES OF ENZYME AND MECHANISM
OF ACTIONS
15.2 COFACTORS
15.3 INHIBITION
15 0 BIOCATALYSIS
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15.1 PROPERTIES OF ENZYME
a) State the properties of enzymes
b) State the six classes of enzyme according
to IUB classificationc) Explain the mechanism of enzyme action
(lowering activation energy)
d) Describe the hypotheses related to its
mechanism of action: Induced fit model,
lock and key model
e) Explain factors that affect the enzymatic
reaction
Learning Outcomes
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Enzyme is a biocatalyst
Bio = life
Catalyse = speed up the rate of reaction.
Definition
Enzyme is a globular proteins which act as
biological catalyst that speed up the rate ofbiochemical reaction in living things by lowering
the activation energy.
Learning Outcomes:
15.1 a) State the properties of enzymes
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Structure of enzyme
Mostly are globularproteins.
Consist of one or several
polypeptide chain with
unique amino acids
sequence.
R groups of amino acids
interact with each otherto form hydrogen bonds,
ionic bonds &
hydrophobic interaction.
Learning Outcomes:
15.1 a) State the properties of enzymes
Structure of Enzyme
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PROPERTIES OF ENZYME
1. Enzymes are highly specific One enzyme acts only on a
specific reactions or a few
related reactions.
Since each enzyme has aunique amino acid sequence,
different interactions between
R groups are formed.
These interactions cause the
polypeptide to fold into a
unique 3 dimensional shape.
Learning Outcomes:
15.1 a) State the properties of enzymes
Structure of Enzyme
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1. Enzymes are highly specific
The shape are highly specific especially at smallpart of enzyme called active site which binds to a
specific substrate.
Learning Outcomes:
15.1 a) State the properties of enzymes
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2. Enzymes remain unchanged at the end of reaction
Enzymes are not altered, destroyed or used by the
reaction it catalyses.
Some enzyme can be used repeatedly.
3. Enzymes are highly efficient
Only smallamount of enzyme is needed to react with
large amount of substrate.
Learning Outcomes:
15.1 a) State the properties of enzymes
Properties of Enzyme
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4. Most catalysed reaction are reversible
An enzyme can catalyse both the forward and reverse
reactions.
5. Does not influence the direction of reaction and final
concentration of products
It only speeds up the rate of reaction.
6. Enzymes activity is influenced by temperature, pH,
substrate & enzyme concentration and inhibitors.
Enzyme activity are maximum at optimum temperature
or PH
can be denatured by extreme temperature or extreme
pH.
Learning Outcomes:
15.1 a) State the properties of enzymes
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15.1 PROPERTIES OF ENZYME
a) State the properties of enzymes
b) State the six classes of enzyme according
to IUB classificationc) Explain the mechanism of enzyme action
(lowering activation energy)
d) Describe the hypotheses related to its
mechanism of action: Induced fit model,
lock and key model
e) Explain factors that affect the enzymatic
reaction
Learning Outcomes
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1. In 1964, IUB (International Union of Biochemistry)
introduced a classification guide of enzymes to
differentiate enzymes.
2. Before it is introduced, it is hard to recognize enzyme
according to traditional way of naming.
3. Eg: pepsin, renin, trypsin
4. Enzymes are classified into 6 main classes according
to the general reaction it catalyses.
ENZYME CLASSIFICATIONLearning Outcomes:
15.1 b) State the six classes of enzyme according to IUB classification
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The Classification of Enzyme
1. Common naming of enzyme usually has 3parts
1) name of substrate
2) type of reaction3) suffix ase
Eg: Alcohol dehydrogenase, RuBP
carboxylase
2. Sometimes, they are named based on the
substrate they act on
3. Eg: sucrase, amylase, lipase, protease
Learning Outcomes:
15.1 b) State the six classes of enzyme according to IUB classification
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Enzyme ClassificationEnzyme group Type of reaction
catalysedEnzyme
examples
1. Oxidoreductase Transfer of O or H atoms or
electrons between
substances, i.e. all
oxidation-reductionreactions.
Dehydrogenase
Oxidase
2. Transferase Transfer of a chemical
group from one substance
to another
Transaminase
Phosphorylase
3. Hydrolase Breaking a molecule into
simpler molecules by
hydrolysis reactions
(addition of water
molecule)
Peptidase
Lipase
Sucrase
Learning Outcomes:
15.1 b) State the six classes of enzyme according to IUB classification
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Enzyme
group
Type of reaction
catalysed
Enzyme
examples
4. Lyase Breaking of a chemical bonds
without the addition of water
(other than by hydrolysis)
Decarboxylase
(remove CO2)
5. Isomerase The rearrangement of atoms
within a molecule converting
from 1 isomer to another
Isomerase
Mutase
6. Ligase Formation of bonds between
two molecules using energyfrom the breakdown of ATP
Synthetase
Learning Outcomes:
15.1 b) State the six classes of enzyme according to IUB classification.
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15.1 PROPERTIES OF ENZYME
a) State the properties of enzymes
b) State the six classes of enzyme according
to IUB classificationc) Explain the mechanism of enzyme action
(lowering activation energy)
d) Describe the hypotheses related to its
mechanism of action: Induced fit model,
lock and key model
e) Explain factors that affect the enzymatic
reaction
Learning Outcomes
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Before any chemical reactions can occur, reactants
must absorb energy to break the existing bonds
before new bonds can be formed.
Definition
The minimumenergy required to break the existing
bond for a chemical reaction to take place is calledactivation energy.
Learning Outcomes:
15.1 c) Explain the mechanism of enzyme action (lowering activation energy)
Activation Energy (Ea)
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The existing bonds start to
break when enough energy isabsorbed.
Reactants become unstable
and very reactive.
This condition is calledtransition state.
By lowering the activation
energy, less energy can be
absorbed to start a reaction.
More reactants can reachtransition state and converted to
products within a short time.
Learning Outcomes:
15.1 c) Explain the mechanism of enzyme action (lowering activation energy)
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Learning Outcomes:
15.1 c) Explain the mechanism of enzyme action (lowering activation energy)
Activation Energy (Ea)
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Learning Outcomes:
14.1 c) Explain the mechanism of enzyme action (lowering activation energy)
Activation Energy (Ea)
L i O
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Substrate binds to enzymes active site to form an
enzyme substrate complex
Bring substrate molecule closer to each other / in
a correct orientation Enzyme stretch / distort the existing bonds
Learning Outcomes:
15.1 c) Explain the mechanism of enzyme action (lowering activation energy)
How Enzyme Lowers the Activation Energy
L i O t
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R group of active sites interact with substrates to
increase the reactivity of the substrate.
These make it easier for substrate to be changed
into product.
Thus, activation energy is reduced without
increasing the temperature in living cells.
Learning Outcomes:
15.1 c) Explain the mechanism of enzyme action (lowering activation energy)
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15.1 PROPERTIES OF ENZYME
a) State the properties of enzymes
b) State the six classes of enzyme according
to IUB classificationc) Explain the mechanism of enzyme action
(lowering activation energy)
d) Describe the hypotheses related to its
mechanism of action: Induced fit model,lock and key model
e) Explain factors that affect the enzymatic
reaction
Learning Outcomes
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1. Proposed by Koshland
(1959).
2. Suggested that theactive site is not exactly
complementary to the
shape of substrate.
3. The active site is
flexible and can change
its shape.
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
Induced fit model
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4. When collisions occur between
enzyme and substrates,substrate can bind to the active
site of the enzyme.
5. The binding of the substrateinduces the enzyme to change
its shape slightly.
6. To enable the substrate to fit
precisely to the active site.
7. An Enzyme-Substrate complex
is formed.
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
O
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8. Enzyme stretched the existing
bond to facilitate the reaction tooccur.
9. Activation energy is reduced,
so it is easier to achieve
transition state.
10. Product is formed and
released from the active site.
11. Enzyme changes back to
original conformation.
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
L i O t
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Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
L i g O t
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Induced fit model
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
L i g O t
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Induced fit model
Learning Outcomes:
15.1d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
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1. Enzyme is very specific because its active site
had a specific shape that fits exactly to a
specific substrate.
2. The shape of active site is rigid.
3. This is called lock and key hypothesis which is
proposed by Fischer (1890).
4. Enzyme is bigger and act as lock.
5. Substrate is smaller and act like a key.
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
Lock & Key model
Learning Outcomes:
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Lock & key model
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
Learning Outcomes:
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Lock & key model
1. The shape of active site isexactly complementary to the
substrate.
2. Substrate binds to the active site
of enzyme to form an enzyme-substrate complex (ES complex).
3. The shape of substrate slightly
changed.
4. Existing bonds are broken.
5. Transition state is achieved,
reaction occurs.
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
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6. Products are formed.
7. The shape of products differ from substrates.8. Thus, products no longer fit into active site.
9. Products are released from active site.
10. Free active site binds with other substrate.
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
Learning Outcomes:
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Lock & key model
Learning Outcomes:
15.1 d) describe the hypotheses related to its mechanism of action: Induced fit model, lock and key model
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15.1 PROPERTIES OF ENZYME
a) State the properties of enzymes
b) State the six classes of enzyme according
to IUB classificationc) Explain the mechanism of enzyme action
(lowering activation energy)
d) Describe the hypotheses related to its
mechanism of action: Induced fit model,lock and key model
e) Explain factors that affect the enzymatic
reaction
Learning Outcomes
Learning outcome:
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1. Substrate concentration
2. pH
3. Temperature
4. Cofactors
g15.1 e) explain factors that effect the enzymatic reaction
Factors affect the enzymatic reaction
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Substrate Concentration
At low substrate
concentration, the rate of
enzyme reaction
increases as substrateconcentration increase.
There are many enzyme
molecules compared to
substrates, not all active
sites are occupied.
g15.1 e) explain factors that effect the enzymatic reaction
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As substrate concentration
increase, more active sites
are occupied until all of them
bind to its substrate.
The rate of reaction reaches
the maximum rate.
Increasing substrate
concentration does not affect
the rate of reaction since allactive sites are saturated with
the substrate.
The graph reaches a plateau.
15.1 e) explain factors that effect the enzymatic reaction
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15.1 e) explain factors that effect the enzymatic reaction
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Most enzyme are effectiveover a narrow PH range.
Maximum enzymes are
effective over a narrow PH
range.
Different enzyme has
different optimum pH value.
Changes in pH above orbelow the optimal pH value
will change the hydrogen
ion (H+) concentration.
pH
15.1 e) explain factors that effect the enzymatic reaction
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15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:) f ff
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This ion changes the ionic
charge of the acidic & basicgroups of amino acids of the
enzyme.
The ionic & hydrogen bonds
that hold the specific 3D
shape of enzyme are
disrupted.
It changes the conformation ofactive sites.
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 ) l i f t th t ff t th ti ti
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Substrate cannot fit into the
active site to form Enzyme-Substrate complex.
Therefore, the rate of reaction
decreases quickly. If the changes of pH is too
high or too low, the active
sites are destroyed causing
the enzyme to denature.
Therefore the rate of reaction
decreases quickly.
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 ) l i f t th t ff t th ti ti
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Enzyme Optimum pHPepsin 2.00
Sucrase 4.50
Enterokinase 5.50
Salivary amylase 7.80
Trypsin 8.00
Pancreatic lipase 9.00
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 ) l i f t th t ff t th ti ti
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All enzymes work withina range of temperaturespecific to organism.
Increases intemperature generallylead to increases inreaction rates.
At low temperatures, anenzyme-catalysedreaction takes placeslowly.
Temperature
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 ) l i f t th t ff t th ti ti
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Hydrogen bond andhydrophobic interactionare not flexible enough.
Induced fit mechanism
is not optimum
Movement of moleculesslow
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 ) l i f t th t ff t th ti ti
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15.1 e) explain factors that effect the enzymatic reaction
As temperature increase, themovement of molecules
increases.kinetic energy ofthe enzyme & substrateincreases.
More collisions occurbetween enzyme andsubstrates to form EScomplex.
The rate of reactionincreases until it reachesoptimum temperature
(usually 35
0
C-40
0
C).
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When temperature
exceeds optimumtemperature, thebonds which hold thespecific 3D shape of
enzyme are broken.
Active sites are
destroyed, enzymedenatured.
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 e) explain factors that effect the enzymatic reaction
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Resulting from the
breakdown of the weakbond such as hydrogenbond, hydrophobicinteraction,disulphide
bridge and Van derWaals
Substrates can nolonger fit into the activesites of the enzyme.
The rate of reactiondecreases quickly.
15.1 e) explain factors that effect the enzymatic reaction
Learning outcome:15 1 e) explain factors that effect the enzymatic reaction
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15.1 e) explain factors that effect the enzymatic reaction