Catalysts are something that speeds up the chemical reaction. Almost all biochemical reactions require catalysts. Enzymes are biocatalysts. Biochemical catalysts speed up the biochemical reactions. In presence of an enzyme, less energy is required for the reaction to take place. A catalyst may be defined as a substance that increases the velocity or rate of chemical reactions without itself undergoing any change in the overall process.

1. ENZYMES
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Prepared by:
Shivanee Vyas
Assistant Professor
SVKM’s, NMIMS, School of Pharmacy and Technology
Management

2. ENZYMES
• Catalysts are something that speeds up the chemical reaction. Almost all biochemical reactions require catalysts.
• Enzymes are biocatalyst. Biochemical catalysts - which speed up the biochemical reactions.
• In presence of an enzyme, less energy is required for the reaction to take place.
• A catalyst may be defined as a substance that increases the velocity or rate of chemical reactions without itself undergoing
any change in the overall process.
• Each enzyme has its own structure & specific confirmation which is necessary for its activity.
• If the enzyme is denatured or dissociated into its subunits, its catalytic activity is lost.
• Therefore 1°, 2°, 3° & 4° structures of protein enzymes are essential for catalytic activity.
• Enzymes have a molecular weight ranging from about 12,000 to 1 million (like proteins).
• Some enzymes require complex organic molecules called coenzymes.

3. • Substrates are the substance on
which enzymes act. Due to the
action of the enzyme, the substrate
is converted into a product. At the
end of the reaction, the enzymes
remain intact. So, the enzyme is not
lost or consumed in the reaction.
• The naming of the enzyme: Names
of most of the enzymes end with
the three letters ‘ase’ This is the
suffix that is added to the name of
the substrate on which the enzyme
act. Ex. Urea is the substrate. The
enzyme that acts on urea is called
urease.

4. 01 02
03 04
(E. C. 1) OXIDOREDUCTASE
(Involved in oxidation-reduction Reaction)
(E. C. 2) TRANSFERASES
(catalyse the transfer of functional group or
radical)
(E. C. 3) HYDROLYASES
(Bring hydrolysis of substrate)
(E. C. 4) LYASES
(Catalyse the removal of groups from larger
substrate)
CLASSIFICATION OF ENZYMES
05 06
(E. C. 5) ISOMERASES
(involved in isomerization reaction)
(E. C. 6) LIGASES
(Catalysing the synthetic reaction)

5. 1. Oxidoreductase ( E.C. 01)- enzymes involved in an oxidation-reduction reaction. E.g.:
Dehydrogenase, oxidase, hydroperoxides.
A red + B ox A ox + B red
2. Transferases (E.C. 02)- enzymes that catalyze the transfer of functional groups. E.g.:
Transaminase, transmethylase.
A – B + C A + C - B
3. Hydrolases (E.C. 03)- enzymes that bring about hydrolysis of various compounds by the addition or
removal of water. E.g.: peptidase, Urease, glucosidases etc.
A – B + H2O A – H + B – OH
4. Lyases (E.C. 04)- enzymes catalyze the removal of groups from the larger substrate. E.g.:
Fumarase, aldoses.
A = B A - B
Oxidoreductase
Transferases
Hydrolases
Lyases

6. 5. Isomerases (E.C. 05)- enzymes involved in all isomerization (one molecule to another)
reactions. E.g.: Retinene isomerase, epimerase etc.
A – B – C A – C – B
6. Ligases (E.C. 06)- enzymes catalyzing the synthetic reactions where two molecules are joined
Together with the utilization of ATP These are also called synthetases. E.g.: acetyl CoA
carboxylase, DNA ligase etc.
A + B + ATP A – B + ADP + Pi

7. PROPERTIES OF ENZYMES
1. Enzymes are BIO-CATALYST.
2. Enzymes are required in small amounts.
3. They quicken the reactions without being consumed or lost
in the reaction or process, without altering reaction
equilibrium.
4. Enzymes are proteins, colloidal in nature & precipitated by
salt solutions.
5. They are inactivated by heat & alteration of pH.
6. Enzymes have great specificity. Each EZ catalyzes one
particular reaction.
7. They are responsible for lowering the activation energy.
8. They possess an active site at which interaction with the
substrate occurs.
9. Some enzymes are regulatory in nature.

8. Mechanism of Action of
Enzyme
Enzyme substrate complex formation
It is essential for enzyme catalysts that the substrate must
combine with the enzyme at the active site to form an
Enzyme-Substrate complex which ultimately results in product
formation. The few theory have been put forth to explain the
mechanism action of enzymes:

9. LOCK & KEY MODEL (Fischer’s Template Theory)
• This was proposed by a German biochemist, Emil Fischer.
• According to this model, the structure or confirmation of the
enzyme is rigid.
• The substrate fits the binding site (active site) just as a key
fits into the proper lock or a hand into the proper glove.
• Thus the active site of an enzyme is a rigid & pre-shaped
template where only a specific substrate can bind.
• This model does not give any scope for the flexible nature
of enzymes.
• Hence the model totally fails to explain many facts of
enzymatic reaction.

10. INDUCED FIT THEORY (Koshland’s Model)
• Koshland in 1958 proposed a more acceptable & realistic
model for enzyme-substrate complex formation.
• According to this model active site is not rigid & pre-shaped.
• The essential features of the substrate binding site are present
at the active site.
• The interaction of the substrate with the enzyme induces
conformation changes in enzymes, resulting in the formation of
a strong substrate binding site.
• Due to induced fit, the appropriate amino acids of the enzyme
are repositioned to form the active site & bring about the
catalysis.
• This model has sufficient experimental evidence from the X-ray
diffraction studies.
• It also explains the action of allosteric modulators &
competitive inhibition on enzymes.

11. FACTORS AFFECTING ENZYME ACTIVITY
1. Effect of Enzyme Concentration
2. Effect of Substrate Concentration
3. Effect of Temperature
4. Effect of pH
5. Effect of Time
6. Effect of Radiation and Light
7. Effect of Enzyme inhibitors

12. 1. Concentration of Enzyme
• As the concentration of enzyme increases the rate of reaction also increases.
• This means enzymatic activity is directly proportional to the concentration of enzymes in the
system.

13. 2. Concentration of Substrate
• If the concentration of enzyme is kept constant & substrate concentration Increases, then the
rate of reaction increases. Initially, the rate is directly proportional to substrate concentration.
• But if the substrate concentration is further raised, the reaction rate remains unchanged.
• As the concentration of substrate increases, the enzyme becomes saturated with substrate.
• At too much concentration of substrate, the enzymes are completely saturated with substrate.

14. 3. Effect of Temperature
• The rate of an enzyme reaction increases with an increase in temperature up to maximum and
then declines. A bell-shaped curve is usually observed.
• A 10ºC rise in temperature will increase the activity of most enzymes by 50 to 100%.
• When the enzymes are exposed to higher temperatures denaturation occurs and enzymes
lose their activity

15. 4. Effect of pH
• An increase in hydrogen ion concentration (pH) influences enzyme activity and a bell-shaped
curve is obtained.
• Enzymes are affected by changes in pH. The most favourable pH value - the point where the
enzyme is most active is known as the optimum pH. (4-9)
• Below and above this optimum pH is much lower, and at extreme pH, the enzymes become
inactive.

16. 5. Effect of Time
• Under ideal optimum condition (when pH & temp. is optimum) the time required for an enzyme
reaction is less.
6. Effect of Light and Radiation
• Enzymes get denatured and deactivated on exposure to ultraviolet, x-rays, α, β, γ rays, etc.
• High energy radiation forms peroxides which oxidize the enzymes & make them inactive.
• Example: salivary amylase is deactivated by UV rays.
7. Effect of Enzyme Inhibitors
• The presence of enzyme inhibitors reduces enzyme action.

17. ENZYMES INHIBITORS
• Enzyme inhibitors are defined as a substance that binds to an enzyme & decreases the
catalytic activity of that enzyme.
• The inhibitor may be organic or inorganic in nature.
• They are classified into 3 types –
1. Reversible Inhibitor
a. Competitive inhibition
b. Non-competitive inhibition
2. Irreversible Inhibition
3. Allosteric Inhibition

18. 1. REVERSIBLE INHIBITION: This inhibitor binds non-covalently (weak bonds) with an
enzyme and inhibition can be reversed if the inhibitor is removed.
b) Non-competitive Inhibition: The inhibitor
binds to the enzyme at a site other than the
active site. The inhibitor has no structural
resemblance with the substrate.
a) Competitive Inhibition: The inhibitor
competes with the substrate and binds at
the active site of an enzyme. This depends
on the concentration of substrate and
inhibitor. They have a similar structure to
that of the substrate.

19. 2. IRREVERSIBLE INHIBITION: The inhibitors bind covalently (tightly) with enzyme and
inactivate them. This deactivation is irreversible. These inhibitors are toxic and poisonous.
Example: Penicillin antibiotics act as irreversible inhibitors of serine containing enzyme and
block bacterial cell wall synthesis.

20. COMPETITIVE ENZYME INHIBITOR NONCOMPETITIVE ENZYME INHIBITOR
The structure of the molecule is similar to that of the
substrate.
The structure of the inhibitor molecule is entirely different
from the substrate.
They better get attached to the active site of the enzyme. The inhibitor forms a complex at a point other than the active
site.
Competitively inhibitors will completely compete with the
substrate for an active site.
Non competitive inhibitor will bind to the allosteric site of the
enzyme, away from the active site.
It compete with the substrate molecule or for the enzyme. It does not compete with the substrate.
It does not alter the structure of the enzyme. It altered the structure of enzyme in such a way that the
substrate may get attached to the active site but not
produced any product.
The reaction can be reversed by increasing the substrate
concentration.
The reaction goes on decreasing as more and more inhibitor
contact the enzyme till saturation is reached.
The effect of competitive inhibitor are usually temporary. The effect of noncompetitive inhibition are permanent.

21. 3. ALLOSTERIC INHIBITION: By the addition of a specific substance i.e. activators or
inhibitors, the rate of reaction is increased or decreased, enzymes which exhibit this
behaviour are called allosteric enzymes. Allosteric enzymes contain a second type of site,
called an allosteric site. The allosteric site, through its binding with a non-substrate molecule,
enhances or impairs the activity of the enzyme.

22. Therapeutic importance of Enzymes
1. The medical significance of enzyme:
• The study of the action of enzymes explains the action of certain drugs which act
as enzyme inhibitors.
• Most of the drugs act by inhibiting certain enzymes. Example: Sulphanilamide kills
pathogenic organisms by inhibiting the folic acid synthetase enzyme (which
synthesizes folic acid).
• The dietary folic acid is utilized by host cells but microorganisms cannot utilize it,
therefore sulphanilamide inhibits reaction which is necessary for bacterial growth.
• Allopurinol is a drug used in the treatment of gout (gout is a disease which results
in a build-up of uric acid in joints and causes arthritis)
2. Enzyme therapy:
• It has been found that enzymes can be used in treatment (to cure disease)
• Example: Asparaginase is an enzyme used for the treatment of tumours.

23. 3. Enzymes act as therapeutic agents:

24. 4. Manufacturing of bulk drugs:
• There are several enzymes that are used to produce various compounds used in
medicines.
• Example: penicillin acylase is used for the production of 6-amino-penicilanic acid
which is used for the manufacturing of various synthetic penicillin.
5. Diagnostic uses of enzymes
• Enzyme levels indicate disease or disorder.
• Human plasma contains many unnecessary enzymes.
• Certain enzymes are present in plasma and are synthesized in the liver, impairment
in liver function often leads to falling in enzyme activity (so a low plasma level of
such enzymes indicates disease).
• There are certain enzymes that are totally absent (low levels) in plasma. If these
enzymes show a rise in plasma level then it indicates disease or disorder.

25. ENZYME DISEASE THAT CAN BE DIAGNOSED
Amylase Acute pancreatitis
Alkaline phosphatase Rickets, Obstructive Jaundice
Creatinine phosphokinase (CPK) Myocardial infraction
Serum Glutamate oxaloacetate transaminase (SGPT) Myocardial infraction
Serum Glutamate pyruvate transaminase (SGOT) Liver disease
Iso-citrate dehydrogenase Hepatitis, liver metastasis
6. Enzymes as Analytical reagents
• Some enzymes are used in laboratory analysis. They give more accurate results than
chemical methods. (ELISA)
• Example: Estimation of plasma glucose by glucose oxidase.

26. 7. Industrial Use
• Enzymes can be used in the textile industry. E.g.: amylase as a softening agent for starched
clothes.
• They can also be used for leather purposes. E.g.: proteolytic purpose.
• Enzymes have importance in the paper Mfg. E.g.: endoxylanases for bleaching of wood pulp.
• They can be used in the manufacturing of organic compounds. E.g.: bacterial enzymes for the
manufacturing of acetone, butanol, lactic acid, etc.
• Beverage industry:- Yeast enzymes are also used in the beverage industry.
• Research:- Several enzymes are used for the detection of biochemical reactions.
• Enzymes can be used in the meat packing industry. Example: papain, in manufacturing of
cheese.
8. Other uses
• Enzymes are essential for the breakdown of nutrients to supply energy and building blocks.
• They assemble these building blocks into proteins, DNA, membranes, cells and tissues

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