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nzymes
ReactionDr. Yogi P. R.
Biochemistry Department
Medical Faculty
Swadaya Gunung Jati University
Cirebon 2009
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Tujuan pembelajaran
Untuk memahami dan mampu menjelaskan
1.Pengertian, karakteristik, dan klasifikasi enzim
2.Fungsi Enzim dalam regulasi reaksi kimiatubuh
3.Faktor-faktor yang mempengaruhi kecepatan
reaksi enzim dan regulasi aktifitas enzim4.Fungsi intraseluler melalui regulasi enzim
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DEFINITION & CHARACTERISTIC
Enzymes are :
- Proteins
- Metabolic catalysts
- The largest and most highly specialized catalysts in the
body for the reactions involved in metabolism whichincrease the rate of chemical reactions by lowering the
activation energy of that reactions
- Unchanged number of enzyme before and after reaction
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E : Enzymes ES : Enzymes+Substrates
S : Substrates P : Product
ES low stability
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Enzyme Function
LOWERING ACTIVATION ENERGY
9Menurunkan energi)
THE FUNCTION OF CATALYST
ENZYME IS A BIOCATALYST
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Site of activity
A. Endoenzyme
Intracellular enzyme : ATP synthesis
A. Eksoenzyme
Extracellular enzyme
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Catalysts effort
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Occurred process
A. Constitutive enzyme
The number of enzyme always constant, not influence
by substrate concentration (tdk berpengaruh olh cubstrat)
A. Adaptive enzyme
The occurred process is stimulated by substrate
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STRUCTURE OF ENZYMES
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Cofactor : Prostetic group
Coenzyme Activator
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COFACTOR COENZYMES
Thiamine pyrophosphate, from Vit. B1, DecarboxylaseFlavin mono/adenine di nuceotide, Vit. B2, Dehydrogenase
Nicatinamide Adenine Dinucleotide/ Phosphate, Nicotinicacid, Dehydrogenase
Coenzyme A, Panthotenic acid, DehydrogenasePyridoxal phosphate, Vit. B6, Transferase
Tetrahydrofolic, Folic acid, Transferase
Deoxyadenosylcobalamine, Vit. B12, Isomerase
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COFACTORS ACTIVATOR
Fe2
+ orFe3
+ in Cytochrome oxidase,
Catalase and Peroxidase
Coin DinitrogenaseK+in Pyruvate kinase
Mg+ in Glucose 6-phosphatase
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Interaction Enzyme-Substrates Model
Lock and key (1890 Emil Fischer)
Stereospecificity catalysts
The shape, or configuration, of the active site is especially
designed for the specific substrate involved
The configuration is determined by the amino acid sequence
of the enzyme, the native configuration of the entire enzyme
molecule must be intact for the active site to have the correct
configurationThe substrate then fits into the active site of the enzyme in
much the same way as a key fits into a lock
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Induced fit (Daniel Koshland)
The binding of a substrate (S) by an enzyme is an interactive
process
The shape of the enzyme's active site is actually modified
upon binding S, in a process of dynamic recognition between
enzyme and substrate called induced fit
In essence, substrate binding alters the conformation of the
protein, so that the protein and the substrate "fit" each other
more precisely
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Specificity Level of Enzymes
1. Bond specificity (Low specificity)
peptidase, phosphatase, esterase
1. Group specificity (Middle specificity) hexokinase
1. Absolute specificity (High specificity)
urease
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Velocity, Enzymes, Substrates
Acceleration of product is determined by enzyme concentration and
substrates concentration
V = Velocity
[E] = Enzyme concentration
[S] = Substrates concentration
A.If the S is CONSTANTThe increase of V is equal with the increase of E
B.If the E is CONSTANT and S increase V will increase proportionally with
the increase of S, but in higher concentration of S, the increasing of V willdecrease slowly until V was almost not suspended from S
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A. B.
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Michaelis Menten Model
Leonor Michaelis & Maud Menten -1913
Konstanta Michaelis-Menten Km = k2+k3/k1
Km = The substrate at wich the velocity of the reaction is half the maximum
velocityKm -- enzyme substrate complex high affinity
Km -- enzyme substrate complex low affinity
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Factors that influence enzymatic reaction
1. Substrates
the substrates concentration will enzymatic reaction
until maximum condition
1. pH
optimum pH will enzymatic reaction
example : Amilase -- optimum pH 5,0
Arginase -- optimum pH 10
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RateofR
eactio
n
Substrate Concentration
Substrate Concentration
Active sites full- maximum turnover
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Rateof R
eaction
pH
1 3 42 5 6 7 8 9
Narrow pH optima
Disrupt Ionic bonds - Structure
Effect charged residues at activesite
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3. Temperature
optimum temp will enzymatic reaction
higher than optimum temp will damage enzyme
( 50C)
If you heat the protein above its optimal
temperature bonds break meaning the protein loses it
secondary and tertiary structure
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Effect of heat on enzyme activty
Denaturing the protein
ACTIVE SITE CHANGES SHAPE
SO SUBSTRATE NO LONGER FITS
Even if temperature lowered enzyme cant regain its correct shape
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4. Inhibitor
Competitive inhibitor Another substance (analog substrates) has similar structure to substrate
Succinate Fumarate
These compete with the substrate molecules for the active site
Always reversible
Increasing substrate concentration to against competitor
SuccinateDehydrogenase
Malonate
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Non-Competitive inhibitor
These are not influenced by the concentration of the substrate
It inhibits by binding irreversibly to the enzyme but not at the active site
Examples Cyanide combines with the Iron in the enzymes cytochrome oxidase
Heavy metals, Ag orHg, combine withSH groups.
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Feed-back inhibitor
The first step (controlled by eA) is often controlled by the
end product (F)
Therefore negative feedback is possible
A B C D E F
The end products are controlling their own rate ofproduction
eFeDeCeA eB
Inhibition
2008 Paul Billiet ODWS
http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html7/29/2019 25081375 Enzymes Reaction
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Alosteric inhibitor
These enzymes havetwo receptor sites
One site fits thesubstrate like otherenzymes
The other site fits aninhibitor molecule
Inhibitor fits
into allosteric
site
Substrate
cannot fit
into theactive site
Inhibitor
molecule
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Five Main Ways that Enzyme Activity is Controlled
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Five Main Ways that Enzyme Activity is Controlled
in The Cell
1. Enzyme production (transcription and translation of enzyme
genes) enhanced or diminished by a cell in response to changesin the cell's environment
This form ofgene regulation is called enzyme induction and inhibition. For
example, bacteria may become resistant to antibiotics such as penicillin
because enzymes called beta-lactamases are induced that hydrolyse the
crucial beta-lactam ring within the penicillin molecule
1. Enzymes can be compartmentalized, with different metabolic
pathways occurring in different cellular compartments
For example, fatty acids are synthesized by one set of enzymes in the cytosol,
endoplasmic reticulum and the Golgi apparatus and used by a different set of
enzymes as a source of energy in the mitochondrion, through -oxidation
http://en.wikipedia.org/wiki/Transcription_%28genetics%29http://en.wikipedia.org/wiki/Translation_%28genetics%29http://en.wikipedia.org/wiki/Regulation_of_gene_expressionhttp://en.wikipedia.org/wiki/Enzyme_induction_and_inhibitionhttp://en.wikipedia.org/wiki/Antibiotic_resistancehttp://en.wikipedia.org/wiki/Penicillinhttp://en.wikipedia.org/wiki/Beta-lactamasehttp://en.wikipedia.org/wiki/Beta-lactamhttp://en.wikipedia.org/wiki/Cellular_compartmenthttp://en.wikipedia.org/wiki/Fatty_acidshttp://en.wikipedia.org/wiki/Cytosolhttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Mitochondrionhttp://en.wikipedia.org/wiki/%CE%92-oxidationhttp://en.wikipedia.org/wiki/%CE%92-oxidationhttp://en.wikipedia.org/wiki/Mitochondrionhttp://en.wikipedia.org/wiki/Golgi_apparatushttp://en.wikipedia.org/wiki/Endoplasmic_reticulumhttp://en.wikipedia.org/wiki/Cytosolhttp://en.wikipedia.org/wiki/Fatty_acidshttp://en.wikipedia.org/wiki/Cellular_compartmenthttp://en.wikipedia.org/wiki/Beta-lactamhttp://en.wikipedia.org/wiki/Beta-lactamasehttp://en.wikipedia.org/wiki/Penicillinhttp://en.wikipedia.org/wiki/Antibiotic_resistancehttp://en.wikipedia.org/wiki/Enzyme_induction_and_inhibitionhttp://en.wikipedia.org/wiki/Regulation_of_gene_expressionhttp://en.wikipedia.org/wiki/Translation_%28genetics%29http://en.wikipedia.org/wiki/Transcription_%28genetics%297/29/2019 25081375 Enzymes Reaction
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3. Enzymes can be regulated by inhibitors and activators
This helps allocate materials and energy economically, and prevents
the manufacture of excess end products. The control of enzymatic
action helps to maintain a stable internal environment in living
organisms
3. Some enzymes may become activated when localized to
a different environment (eg. from a reducing (cytoplasm)
to an oxidising (periplasm) environment, high pH to low pH
etc).For example, hemagglutinin in the influenza virus is activated by a
conformational change caused by the acidic conditions, these occur
when it is taken up inside its host cell and enters the lysosome
http://en.wikipedia.org/wiki/Enzyme_inhibitorhttp://en.wikipedia.org/wiki/Homeostasishttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Periplasmhttp://en.wikipedia.org/wiki/Hemagglutininhttp://en.wikipedia.org/wiki/Influenzahttp://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Lysosomehttp://en.wikipedia.org/wiki/Influenzahttp://en.wikipedia.org/wiki/Hemagglutininhttp://en.wikipedia.org/wiki/Periplasmhttp://en.wikipedia.org/wiki/Cytoplasmhttp://en.wikipedia.org/wiki/Homeostasishttp://en.wikipedia.org/wiki/Enzyme_inhibitor7/29/2019 25081375 Enzymes Reaction
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5. Enzymes can be regulated through
post-translational modification.
For example, in the response to insulin, the phosphorylation of multiple
enzymes, including glycogen synthase, helps control the synthesis or
degradation ofglycogen and allows the cell to respond to changes in
blood sugarAnother example of post-translational modification is Chymotrypsin, a
digestive protease, is produced in inactive form as chymotrypsinogen in
the pancreas and transported in this form to the stomach where it is
activated. This stops the enzyme from digesting the pancreas or other
tissues before it enters the gut. This type of inactive precursor to anenzyme is known as a zymogen.
http://en.wikipedia.org/wiki/Post-translational_modificationhttp://en.wikipedia.org/wiki/Insulinhttp://en.wikipedia.org/wiki/Phosphorylationhttp://en.wikipedia.org/wiki/Glycogen_synthasehttp://en.wikipedia.org/wiki/Glycogenhttp://en.wikipedia.org/wiki/Blood_sugarhttp://en.wikipedia.org/wiki/Chymotrypsinhttp://en.wikipedia.org/wiki/Proteasehttp://en.wikipedia.org/wiki/Chymotrypsinogenhttp://en.wikipedia.org/wiki/Pancreashttp://en.wikipedia.org/wiki/Stomachhttp://en.wikipedia.org/wiki/Zymogenhttp://en.wikipedia.org/wiki/Zymogenhttp://en.wikipedia.org/wiki/Stomachhttp://en.wikipedia.org/wiki/Pancreashttp://en.wikipedia.org/wiki/Chymotrypsinogenhttp://en.wikipedia.org/wiki/Proteasehttp://en.wikipedia.org/wiki/Chymotrypsinhttp://en.wikipedia.org/wiki/Blood_sugarhttp://en.wikipedia.org/wiki/Glycogenhttp://en.wikipedia.org/wiki/Glycogen_synthasehttp://en.wikipedia.org/wiki/Phosphorylationhttp://en.wikipedia.org/wiki/Insulinhttp://en.wikipedia.org/wiki/Post-translational_modification7/29/2019 25081375 Enzymes Reaction
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Thanks
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