ENZYMES

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ENZYMES
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ENZYMES

Elino, M.M.H.
OVERVIEW of ENZYMES
Enzymes are biologic catalysts. Catalysts
are substances that increase the speed of a
chemical reaction, it is not permanently changed,
nor does it cause the reaction to occur, that is,
a catalyst can increase the speed of a reaction
but cannot cause that reaction if it would not
occur in the absence of catalyst. Since catalysts
are not used up, they can be used over and over
again.
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ENZYMES

Elino, M.M.H.
OVERVIEW of ENZYMES
Enzymes are organic catalyst produced by an
organisms. The reactant in an enzyme-catalyzed
reaction is called substrate.
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ENZYMES

Elino, M.M.H.
OVERVIEW of ENZYMES
The small portion of the molecule that is
responsible for the catalytic action of the
enzyme is the active site.
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ENZYMES

Elino, M.M.H.
OVERVIEW of ENZYMES
Enzymes are superior to other catalysts in
several ways 1. They have a much greater
catalytic power.
CO2 H2O carbonic anhydrase H2CO3
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ENZYMES

Elino, M.M.H.
OVERVIEW of ENZYMES
2. Enzymes are highly specific with varying
degrees of specifity. Absolute specifity they
act on one substrate and only on that
substrate. Stereospecifity such enzymes that
can detect the difference between optical
isomers (mirror images) and select only one of
such isomers. Reaction specifity enzymes that
catalyze certain types of reactions.
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ENZYMES

Elino, M.M.H.
OVERVIEW of ENZYMES
Group specifity enzymes that catalyzes a group
of substances that contain specific
compounds. 3. The activity of enzymes is closely
regulated, whereas the catalyst is difficult to
control.
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ENZYMES

Elino, M.M.H.
ENZYME REACTION
Enzymes are proteins and therefore undergo all
the reactions that proteins do. That is, enzymes
can be coagulated by heat, alcohol, strong
acids, and alkaloidal reagents. Temperature
Requirement The higher the temperature, the
faster the rate of reaction. The best temperature
for enzyme function the temperature at which
the rate of a reaction involving an enzyme is the
greatest is called the optimum temperature.
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ENZYMES

Elino, M.M.H.
ENZYME REACTION
Role of pH Each enzyme has a pH range within
which it can best function. This is called
optimum pH range for that particular enzyme.
For example, the optimum pH range of pepsin, an
enzyme found in gastric juice, is approximately
2.0, whereas the optimum pH range of trypsin, an
enzyme found in pancreatic juice, is near 8.2.
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ENZYMES

Elino, M.M.H.
ENZYME REACTION
If the pH of a substrate is too far from the
optimum pH required by the enzyme, that enzyme
cannot function at all. However, since body
fluids contains buffers, the pH usually does not
vary too far from the optimum values.
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ENZYMES

Elino, M.M.H.
ENZYME REACTION
Effect of Concentration As with the all
chemical reactions, the speed is increased with
an increase in concentration of reacctants. With
an increased concentration of substrate, the rate
of the reaction will increase until available
enzyme becomes saturated with substrate. Also
with an increase in the amount of enzyme, the
rate of reaction will increase, assuming an
unlimited supply of substrate.
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ENZYMES

Elino, M.M.H.
ACTIVATORS and INHIBITORS
Activators inorganic substances that tend to
increase the activity of enzyme. Inhibitors
any substance that will make the enzyme less
active or render it inactive. Competitive
inhibitors binds reversibly in the active site
and so block the access by the substrate. Incomp
etitive inhibitors bind to another site on the
enzyme to render it less active or inactive.
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ENZYMES

Elino, M.M.H.
ACTIVATORS and INHIBITORS
Irreversible inhibitors form strong covalent
bonds with the enzymes, rendering it inactive.
This effect cant be overcome by increasing the
concentration of the substrate.
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ENZYMES

Elino, M.M.H.
ACTIVATORS and INHIBITORS
Poisons Many enzymes inhibitors are poisonous
because their effect on enzyme activity. Mercury
and Lead compounds are poisonous because they
react with sulfhydryl groups ( - SH) of an
enzymes and so change its conformation. The
subsequent loss of enzyme activity leads to the
various symptoms of lead and mercury poisoning,
such as loss of equilibrium, hearing, sight, and
touch, which are generally irreversible.
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ENZYMES

Elino, M.M.H.
ACTIVATORS and INHIBITORS
Drugs While some enzyme inhibitors are
poisonous, others are beneficial to life.
Pencillin acts as an enzyme inhibitor for
transpeptide, a substance that bacteria need to
build their cell walls. If the cell wall is
lacking, osmotic pressure causes the bacterial
cell to burst and die. However, new strains of
bacteria have developed an enzyme, penicillinase,
that inactivates penicillin. To destroy these new
strains, synthetically modified penicillins have
been prepared so that this antibiotic remains
effective.
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ENZYMES

Elino, M.M.H.
MODE OF ENZYME ACTIVITY
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ENZYMES

Elino, M.M.H.
MODE OF ENZYME ACTIVITY
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ENZYMES

Elino, M.M.H.
ACTIVATORS and INHIBITORS
Lock-and key Model Wherein the substrate must
fit into the active site of the enzyme hence
the specifity of the enzyme. Induced-Fit
Model Suggests that the active site is not
rigid as the Lock-and-Key Model, but flexible.
That is, the site changes in conformation upon
binding to a substrate in order to yield an
enzyme-substrate fit.
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ENZYMES

Elino, M.M.H.
APOENZYMES and COENZYMES
Other enzymes are conjugated proteins they
contain a protein and non-protein part. Both
parts must be present before the enzyme can
function. The protein part is called the
apoenzyme and the non-protein (organic part) is
called coenzyme.
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ENZYMES

Elino, M.M.H.
APOENZYMES and COENZYMES
Coenzymes are not proteins and so are not
inactivated by heat. Examples of coenzymes are
the vitamins or compounds derived from vitamins.
The reaction involving a coenzyme can be written
as follows coenzyme apoenzyme
enzyme Coenzyme A is essential in the
metabolism of carbohydrates, lipids, and proteins
in the body.
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ENZYMES

Elino, M.M.H.
NOMENCLATURE
Formerly enzyme were given names ending in
-in. With no relation being an indicator
between the enzyme and the substance it affects
the substrate. The current system for naming
enzymes uses the name of the substrate or the
type of reaction involved, with the ending -ase.
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ENZYMES

Elino, M.M.H.
NOMENCLATURE
ENZYME SUBTRATE or REACTION TYPE
Maltase Maltose
Urease Urea
Proteases Proteins
Carbohydrases Carbohydrates
Lipases Lipids
Hydrolases Hydrolysis Reaction
Deaminases Removing amines
Dehydrogenases Removing hydrogens
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ENZYMES

Elino, M.M.H.
CLASSIFICATION
Oxidoreductases are enzymes that catalyze
oxidation-reduction reactions between two
substrates. The enzymes of the
oxidation- reduction reactions in the body are
important because these reactions are
responsible for the production of heat and
energy. Transferases are enzymes that catalyze
the transfer of a functional group between two
substrates.
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ENZYMES

Elino, M.M.H.
CLASSIFICATION
Hydrolases hydrolytic enzymes catalyze the
hydrolysis of carbohydrates, esters and
proteins. Lyases are enzymes that catalyzes
the removal of groups from substrates by means
other than hydrolysis, usually with the
formation of double bonds.
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ENZYMES

Elino, M.M.H.
CLASSIFICATION
Isomerases are enzymes that catalyze the
interconversion of cis-trans isomers. Ligases
or synthetases, are enzymes that catalyze the
coupling of two compounds with breaking of
pyrophosphate bonds.
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ENZYMES

Elino, M.M.H.
ENZYMES of the KIDNEY
If an individuals blood pressure drops, as in
the case of hemorrhaging or in hypokalemia, the
kidneys secrete the enzyme renin (sometimes
considered as a hormone) into the
bloodstream. angiotensinogen renin
angiotensin I converting enzyme
angiotensin II Angiotensin II increases the
force of the heartbeat and constricts the
arterioles, thus causing an increase in blood
pressure.
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ENZYMES

Elino, M.M.H.
ENZYMES of the KIDNEY
Angiotensin II brings about the contraction
of smooth muscle and also triggers the release of
the hormone aldosterone which aids in the
retention of water. Actually, angiotensin I is
the most powerful vasoconstrictor known. It is an
octapeptide Angiotensin I is a decapeptide.
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ENZYMES

Elino, M.M.H.
ENZYMES of the KIDNEY
Other kidney enzymes include glucose-6-phosphatas
e, which is involved in the removal of the
phosphate group from glucose-6-phosphate, thereby
enabling glucose to diffuse from the cell into
the blood stream Glutaminase, which is
involved in the conversion of glutamine into
glutamic acid and NH4 and a hydroxylase,
which is involved in the synthesis of calcitriol.
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ENZYMES

Elino, M.M.H.
CHEMOTHERAPY
Chemotherapy is the use of chemicals to destroy
infectious microorganisms and cancerous cells
without damaging the hosts cells. These
chemicals function by inhibiting certain
cellular enzyme reactions. Among the
chemotherapeutic agents are the antibiotics and
the antimetabolites.
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ENZYMES

Elino, M.M.H.
CHEMOTHERAPY
Antibiotics are compounds produced by one
microorganisms that are toxic to another
microorganisms. Among the most commonly used
are the penicillin and tetracyclin.
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ENZYMES

Elino, M.M.H.
CHEMOTHERAPY
Penicillin
Tetracycline
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ENZYMES

Elino, M.M.H.
CHEMOTHERAPY
Antimetabolites are chemicals that have
structures closely related to those of the
substrate enzymes act on, thus inhibiting
enzyme activity. Mercaptopurine are used in
the treatment of leukemias. Some are
antibiotics.
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ENZYMES

Elino, M.M.H.
CHEMOTHERAPY
One of the most promising new chemotherapeutic
agent in decades is taxol, a natural product
obtained from the bark of Pacific yew trees.
Taxol acts by interfering with cellular growth
and function and is very effective in shrinking a
variety of tumors, particularly in advanced cases
of ovarian and breast cancer.
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ENZYMES

Elino, M.M.H.
CLINICAL SIGNIFICANCE OF PLASMA ENZYME
CONCENTRATIONS
The measurement of plasma enzyme levels can
be of great diagnostic value. Many other plasma
enzymes are useful in the diagnosis of various
diseases.
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ENZYMES

Elino, M.M.H.
CLINICAL SIGNIFICANCE OF PLASMA ENZYME
CONCENTRATIONS
SERUM ENZYME MAJOR DIAGNOSTI C USE
Glutamic oxaloacetic transaminase (SGOT) Myocardial Infarction
Glutamic pyruvic transaminase (SGPT) Infectious Hepatitis
Trypsin Acute pancreatic disease
Ceruloplasmin Wilsons Disease
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ENZYMES

Elino, M.M.H.
CLINICAL SIGNIFICANCE OF PLASMA ENZYME
CONCENTRATIONS
SERUM ENZYME MAJOR DIAGNOSTI C USE
Amylase Liver and pancreatic disease
Acid phosphate Prostate Cancer
Alkaline phosphatase Liver or bone disease
Creatine phosphokinase Myocardial infarction, muscle disorders
Lactate dehydrogenase Myocardial Infarction, leukemia, anemia
Renin Hypertension
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ENZYMES

Elino, M.M.H.
ISOZYMES
Isozymes or Isoenzymes are enzymes with the
same function but slightly different structural
features. The reason for their existence is not
unknown, but they are made use of clinically.
Lactate dehydrogenase (LDH), creatine kinase, and
alkaline phosphatase all occur in isoenzyme form
and are diagnostic value. LDH has five forms.
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ENZYMES

Elino, M.M.H.
CLINICAL SIGNIFICANCE OF RELATIVE AMOUNT OF LDH
Condition Isoenzyme Pattern
Myocardial Infarction Moderate elevation of LDH1 Slight elevation of LDH2
Acute Hepatitis Large elevation of LDH5 Moderate elevation of LDH4
Muscular Dystrophy Elevation of LDH1, LDH2, LDH3
Megaloblastic Anemia Large elevation of LDH1
Sickle-cell Anemia Moderate elevation of LDH1, LDH2
Arthritis with Joint effusions Elevation of LDH5
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ENZYMES

Elino, M.M.H.
ALLOSTERIC REGULATION
Allosteric regulation  is the regulation of
an enzyme or other protein by binding
an effector molecule at the enzyme's allosteric
site (that is, a site other than the  active
site). Effectors that enhance the protein's
activity are referred to as allosteric enzymes,
whereas those that decrease the protein's
activity are called noncompetitive inhibitors.
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ENZYMES

Elino, M.M.H.
ALLOSTERIC REGULATION
Allosteric regulation   This control of key
enzymes is utmost importance to ensure that
biologic processes remain coordinated at all
times to meet the immediate metabolic needs of
the cells.
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ENZYMES

Elino, M.M.H.
ZYMOGENS
Zymogens are inactive pprecursors of enzymes.
Most digestive and blood-clotting enzymes exist
in the zymogen form, until activated. In the
case of digestive enzymes, this is necessary to
prevent digestion of pancreatic and gastric
tissue. For blood clotting, it is to avoid
premature of blood cells.
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ENZYMES

Elino, M.M.H.
ZYMOGENS
ZYMOGEN ACTIVE FORM OF ENZYME
pepsinogen pepsin
trypsinogen trypsin
prothrombin thrombin
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ENZYMES

Elino, M.M.H.
ZYMOGENS
Lactose Intolerance Individuals who cannot eat
food containing lactose are said to be lactose
intolerant. They lack enzyme lactase, which is
requires for the hydrolysis of lactose. As a
result, lactose acuumulates in the intestinal
tract and pulls water out of the tissues by
osmosis. This is turn causes abdominal cramps,
distention, and diarrhea.
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ENZYMES

Elino, M.M.H.
ZYMOGENS
Lactose Intolerance To overcome such an
effect today, an individual may take Lactaid
orally to supply the missing enzyme.
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