Introduction, Nomenclature of enzymes, Classification of enzymes on the basis of site of action, on the reaction of catalysis and Classification depends upon substrates on they which act, Specificity of Enzymes, Active Site of An Enzyme: 1. Lock-key model 2. Induce fit model, Factors Affecting Enzymes Reaction, Enzyme 1.Inhibition Competitive inhibition, 2. Non-Competitive inhibition, Isoenzymes, Allosteric Enzymes, Co-Factors, Turnover Number of An Enzyme, Pharmaceutical Importance Of Enzymes,

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Enzymes
Presented By
Ms. Monika Maske
Assistant Professor
M. Pharm
( Pharmaceutical Chemistry)
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Introduction
 Enzymes increases the rate of reaction, without altering its
equilibrium.
 They are initially produced in cell an some are excreted
through cell wall and function in the surrounding
environment.
 Enzymes are proteins that act as catalysts for biochemical
reactions.
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 Almost all biochemical reactions require catalysts.
 Recently, observed that some RNA molecules have
catalytic activity.
 The term first introduced by KUHNE in 1878.
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Nomenclature of Enzymes
 The word enzyme is formed from two Greek words: En
means inside and zyme, which means yeast i.e., the word
enzyme means inside yeast.
 There are many methods for naming enzymes:
 1- The old trivial name as pepsin and trypsin.
 2- The name of substrate and the suffix – ase
 added to it as lactase acting on lactose.
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 3- Two words, one for the substrate and the other for the
type of reaction e.g. Succinate dehydrogenase, pyruvate
decarboxylase and glutamine synthetase.
 Enzymes are generally named according to the reaction they
catalysed or by suffixing “ase” after the name of substrate.
 The International Union of Biochemistry and Molecular
Biology developed a nomenclature for enzymes.
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 Each enzyme described by a sequence of four numbers
preceded by “EC”.
 EC denotes Enzyme Commission and the no. of enzyme is
called EC number.
 When classified, each enzyme is assigned the Ec number,
in the form of digits separated by dots.
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 The first digit denotes the class (reaction type) of the
enzyme.
 second digit denotes the functional group (subclass) upon
which the enzyme acts.
 The third digit denotes the coenzyme(sub-subclasses).
 The fourth digit denotes the substrate (serial no. identify
enzyme within sub-subclass).
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 The class, subclass and sub-subclass provide additional
information about the reaction classified.
 The last printed list of enzymes appeared in year 1992.
since then it has been updated and maintained online.
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Sr. No Name of substrate or Reaction Enzyme
1 Urea Urease
2 Maltose Maltase
3 Protein Protease
4 Carbohydrate Carbohydrase
5 Reduction Reductase
6 Group transfer Transferase
7 Isomerisation Isomerase

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Classification of Enzymes
 The classification is based on the reaction of catalysis.
1. Oxido-reductases: Enzymes catalyse redox reactions, i.e. the
removal of hydrogen or addition of oxygen.
- These reaction catalysed by enzyme succinate dehydrogenase.
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2. Transferases: It transfer groups like –NH3, -CH3, -CH2OH.
- These carried out by transferase enzymes.
- It transfers the amino group from an amino acid to alpha-keto
acid.
3. Hydrolases: These enzymes catalyze the hydrolytic cleavage
reaction.
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4. Lyases: These enzymes catalyse the cleavage reactions
which are non-hydrolytic.
- Ex. Aldolase, histidase etc.
5. Isomerases: These enzyme responsible for the
isomerization reaction.
- These reaction requires dextrose isomerase enzyme.
Dextrose Fructose
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6. Ligases: These enzymes catalyse the formation of bonds.
- ex. DNA ligase
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Classification On The Basis of Site of Action
a) Endoenzymes- Which act only inside the cell are known
as endoenzymes or intracellular enzymes.
- It involves the synthesis of cell components, food reserves
& bioenergetic i.e liberation of energy from food.
- Ex. Isomerases, Phosphorylases.
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b) Exoenzymes- The enzymes which are secreted outside the
cell are known as exoenzymes or extracellular enzymes.
- These are normally digestive in their function.
- They hydrolyse very complex molecules into simple
compounds i.e. proteoses, lypases acting on proteins, lipids
respectively.
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c) Constitutive Enzymes: These enzymes are produced in
absence of substrate are known as constitutive enzymes.
- Which produced in constant rate, in constant amounts of
metabolic state of organism.
- These are part of basic & permanent enzymic action of
cell.
- Ex. Enzymes of glycolytic series.
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d) Induced Enzymes: These are present in trace amounts but
their conc. Gets immediately increased in presence of
substrate on which they act.
- Microorganisms produce them in response to the
presence of substrate in the environment only known as
induced enzymes.
- Ethanol, barbiturates are powerful in inducing hepatic
microsomal enzymes.
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Classification of Enzymes
 Classification depends upon substrates on they which act.
A. Amylolytic enzymes or Carbohydrases: Enzymes which
act on only on carbohydrates known as amylolytic or
carbohydrases.
1. Amylopsin or Diastase
2. Ptyalin
3. Malt-diastase
4. Invertase
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5. Maltase
6. Zymase
7. Emulsin
8. Myrosin
9. Hemicellulose
10. Hyaluronidase
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B. Proteolytic Enzymes or Proteases: This enzymes act on
proteins & hydrolose them.
1. Trypsin 6. Fibrinolysin
2. Chymotrypsin 7. Eurokinase
3. Pepsin 8. Streptokinase
4. Renin 9. Papain
5. Muramidase 10. Bromelain
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3. Lypolytic Enzyme: Enzymes which act on fats or lipids.
1. Lypase
2. Steapsin
3. Pancreatin
4. Fungal lipase
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Enzyme Catalysed reactions
 The reactants, which are transformed in an enzymic
reaction are called the substrates.
 During enzymic reaction the substrate is converted into a
product.
 Let us consider a general reaction;
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E + S K1, K2 ES K3 E + P
Where, [E]- Enzyme Conc.
[ES]- Enzyme substrate complex conc.
[S]- Substrate conc.
[P]- Product conc.
While, K1, K2 and K3 are equilibrium constants.
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 Enzymes increases the rate of biochemical reaction by
reducing the energy of activation, without shifting the
chemical equilibrium
 The substrate is converted to product.
 The reaction is carried out in absence of enzyme, the
energy of activation is high.
 In presence of enzyme, the energy of activation is
reduced.
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Specificity Of Enzymes
 Enzymes are highly specific in their action.
 Inorganic catalysts are not specific in their action.
 It is important feature of enzymes.
 Man-made catalysts, they vary in their degree of
specificity.
 Some have absolute specificity.
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 Ex. Aspartate is an example of absolute specification.
 Aspartate acts only on fumarate to produce L-aspartate.
 Some enzymes can act on a wide variety of substrates, they
are structurally related.
 These types of enzyme have broad specificity.
 Aspartates converts fumarate & not to D-aspartates.
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Active Site of An Enzyme
 It is a portion of an enzyme, to which the substrate binds
& gets converted into the product.
 The substrate binds with enzyme with the help of weak
ionic interactions like H-bonds.
 Conformation of active site:- The binding of a substrate
with an enzyme at the active site, it explain by 2 models.
1. Lock-key model
2. Induce fit model
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A) Lock-key model- The shape of active site and substrate is
complementary to each other.
- The substrate molecule fits into the site of an enzyme just
as key fits into a lock.
- This model shape of active site is rigid & complementary
to the shape of substrate molecules.
- These model cannot explain the broad specificity of some
enzyme.
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B) Induce Fit Model- In this modal the active site of an
enzyme is considerably flexible.
- So wide variety of substrate molecules.
- The shape of active site is ,made complementary to the
substrate to certain extent thus, the substrate binds with
the enzyme hence, called as induced fit model.
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Factors Affecting Enzymes Reaction
1. Effect of substrate concentration (Michaelis-Menten
Equation)-
o Keep enzyme conc. is constant, increase in the conc. of
substrate, results the rate of reaction increases.
o The initial stage, rate is directly proportional to the
substrate conc.
o If substrate conc. further increased, velocity of reaction
remains unchanged.
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o Enzymes are completely saturated with the substrate,
the velocity at this stage is called the maximum velocity
denoted by V or Vmax.
o Rate equation of enzyme catalysed reaction
o Km called the Michaelis Menten constant.
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o It define as substrate conc. At which the velocity of an
enzyme catalysed reaction is exactly half of V or Vmax.
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o The rate of equation of an enzyme catalysed reaction can
be transformed to its inverse form & is called the
Linweaver Burk equation.
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2. Enzyme Concentration –
o Enzymic activity is directly proportional to the Conc. Of
enzyme.
o Enzymes are usually present in very low molar conc.
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3. Effect of pH-
o Most enzymes have a characteristics pH at which their
activity is maximum.
o Going below & above this pH, the activity declines. This
characteristic pH is called the optimum pH of an enzyme.
o pH activity relationship of any enzyme depends on the
acid-base properties of enzyme & substrate, and on other
factors.
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o It is not necessary that optimum pH of enzyme identical to
normal intercellular pH.
o Trypsin has optimum pH about 8 hence, buffer is needed
for action of enzymes to maintain the pH.
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4. Effect of Temperature-
o The rate of enzyme catalysed reactions increases as the
temperature increases upto the optimum temp.
o Further rise in temp. decreases the velocity of reaction.
o The temp. at which enzyme shows maximum active.
o Further rise in temp. results in inactivation of enzyme
called as thermal denaturation.
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5. Effect of Inhibitors –
o Presence of enzyme inhibitors reduces the enzyme action.
o Heavy metals are the inhibitors for enzyme activity.
6. Effect of Activators –
o Presence of activators in certain conc. Increases the
enzyme activity.
o Cysteine HCl increases the proteolytic activity of papain.
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7. Effect of Radiation & Light –
o Some enzymes may be deactivated by exposure to UV,
beta, gamma and X-rays.
o Ex. Salivary amylase is deactivated by exposure to UV
rays.
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Enzyme Inhibition
o The functional grp. Of enzymes, from their active site &
surfaces, react with a varity of chemical reagents & their
catalytic activity is reduced.
o These reagents are called inhibitors and process is called
enzyme inhibition.
o Some are non-physiological in origin.
o These inhibitors regulate the activity of enzymes.
o According to mode of action , it classified as
1. Competitive inhibition
2. Non-Competitive inhibition
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1. Competitive inhibition
o A competitive inhibitor often has structural features
similar to those of the substrate whose reactions they
inhibit.
o The inhibitor and the substrate both are competing for the
active site of an enzyme it is called competitive inhibition.
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43. z2. Non-Competitive inhibition
o These are not influenced by the conc. of the substrate.
o It inhibits by binding irreversibly to the enzyme but not at
the active site.
o They also bind with the same affinity to the free enzyme &
form the Enzyme-Substrate complex.
o It change the shape of enzyme & active site.
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Isoenzymes
o The enzymes which have multiple molecular forms in the
same organism, catalysing the same biochemical reaction are
called isoenzymes.
Lactate + NAD+ Pyruvate + NADH+ H+
o These reaction is catalysed by enzyme lactate dehydrogenase
which is present in five different molecular forms in the
tissues.
o All have different amino acid composition & sequence.
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Allosteric Enzymes
o These are regulatory enzyme.
o The catalytic activity is regulated by itself.
o The regulation is mediated via specific metabolites.
o These metabolites are called allosteric modulators.
o Allosteric enzymes have allosteric site, in addition to the
active site to which allosteric modulator binds.
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o 2 types of allosteric modulators,
o Positive allosteric modulators if they increase the activity
of an enzyme.
o Negative allosteric modulators which reduces the activity
of an enzyme.
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Co-Factors
o Some enzymes requires a non-protein moiety for catalytic
activity which is called as a co-factor.
o Some co-factors derived from vitamins they called as co-
enzymes.
o Co-enzymes are low mol. wt. organic substances, derived
from vitamins.
o Ex. Pyridoxal phosphate is derived from vit. B6 which is a
co-enzyme of transaminase.
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o There are some enzymes which require metal ions for
their catalytic activity called as metal co-factor.
o Ex. Zinc is required for carboxypeptidase.
Enzyme activity units
o Amounts which causes transformation of 1.0μ mole (106)
of substrate per minute at 250 C, under optimal condition
of measurement.
o Specific activity defined as the no. of enzymes unit per
milligram of protein.
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Turnover Number of An Enzyme
o It is the number of substrate molecules transformed per
minute by a single enzyme molecule when the enzyme
conc. is the rate limiting factor.
o Feed back inhibition:- In some enzymes, their activity is
inhibited by their product or the successive metabolites of
the metabolic pathway called as feed back inhibition.
o The metabolite D inhibits enzyme E1 this called feed back
inhibition.
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Pharmaceutical Importance Of Enzymes
1. Medicinal significance of enzymes:-
o The mode of action of enzymes explains the action of
certain drugs which are enzyme inhibitors, these types of
drugs belongs to class antimetabolite
o Allopurinal is used in treatment of gout, it prevents the
formation of uric acid.
o It is competitive inhibitors of xanthin oxidase.
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2. Enzyme Therapy:- Enzymes can used for treatments like
tumours, lactose in tolerance in children.
3. Manufacturing of Bulk Drugs:- Some enzymes used for
mfg. of bulk drug like penicillin acylase for production of 6-
amino-penicilanic acid (6 AP).
o Urokinase in cardiac diseases, streptokinase in treatment
of thrombosis.
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4. Diagnostic Uses of Enzymes:- Enzymes are known as
marker of cellular damage.
o The amount of enzymes present in the plasma is used for
investigation of diseases of liver, heart, skeletal muscle,
etc.
o Aspartate amino transfererase and lactate dehydrogenase
are seen in cardiac and hepatic tissues.
o Trypsin enzyme seen in stomach causes liver diseases and
malnutrition.
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5. Medicinal and Clinical uses:-
o Enzymes can be used for Aiding Digestion. Ex. Amylases,
Lipase and proteases.
o Used as Deworming agents. Ex. Papain.
o Enzymes act as anti-clotting agents like fibrinolytic and
thrombolytic. Ex. Urokinase, streptokinase.
o Can be used as surface disinfectants. Ex. Trypsin.
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o Used in the diagnosis purpose. Ex. Glucose oxidase along
with peroxidase to detect the level of glucose.
Liver disease: SGPT, SGOT
Heart attacks (MI): SGOT
6. Industrial Purpose:-
o Enzyme can be used in textile industry.
o Used for leather purpose.
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o Used in paper manufacturing, organic compounds
manufacturing like lactic acid.
7. Enzymes as food and in Food Industry:-
o Enzymes can be used in the meat packing industry.
8. Research:- Several enzymes are used for detection of
biochemical reactions.
9. Beverage industry:- Papain is used to stabilize chill proof
bear.
o Yeast enzymes are used in beverage industry.
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Thank You
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