Enzymes are proteins that act as biological catalysts, regulating the rate of chemical reactions without being altered themselves. There are six classes of enzymes: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Enzymes catalyze reactions via two mechanisms: the lock and key model where the active site perfectly binds the substrate, and the induced fit model where substrate binding causes a conformational change that forms the active site. Enzymes accelerate reactions by lowering their activation energy through releasing binding energy upon substrate binding in the active site.

1. Enzymes
DEEPAK MAURYA
M.PHARM
(PHARMACEUTICAL CHEMISTRY)

2. Enzymes-
Enzymes are proteins that act as biological
catalysts.
Enzyme, a substance that acts as a catalyst in
living organisms, regulating the rate at
which chemical reactions proceed without
itself being altered in the process.

3. Classifications-
 According to the International Union of Biochemists (I U B),
enzymes are divided into six functional classes -
Types Biochemical Property
Oxidoreductases -
The enzyme Oxidoreductase catalyzes the oxidation reaction where the electrons tend to travel from one
form of a molecule to the other.
Transferases -
The Transferases enzymes help in the transportation of the functional group among acceptors and donor
molecules.
Hydrolases -
Hydrolases are hydrolytic enzymes, which catalyze the hydrolysis reaction by adding water to cleave the
bond and hydrolyze it.
Lyases - Adds water, carbon dioxide or ammonia across double bonds or eliminate these to create double bonds.
Isomerases -
The Isomerases enzymes catalyze the structural shifts present in a molecule, thus causing the change in the
shape of the molecule.
Ligases - The Ligases enzymes are known to charge the catalysis of a ligation process.

4. Mechanism of enzyme
action-

5. Theory of enzymes -
Based on two models-
1) Lock and Key models
2) Induced fit model

6. Continue…
 1) Lock and Key models-
 The active site of the enzyme is complementary in conformation to the
substrate, so that enzyme and substrate “recognise” one another.

7. Continue…
2) Induced fit model-
The active sites of some enzymes assume a shape
that is complementary to that of the transition state
only after the substrate is bound. • The active site is
flexible, not rigid. • Substrate binding brings
conformation changes in active site – nascent active
site •

8. Continue…
Induced fit model-

9. How enzyme catalyze the reaction

10. Continue…
• Enzymes are catalyst that accelerate the rate of biochemical
reaction by decreasing the energy of activation.
• Every chemical reaction have energy barrier that must be crossed
by the reactant molecules in order to convert itself into the product.
• The amount of energy supplied to reactant molecules in order to
cross the energy barrier to from product is known as Energy of
activation.
• If energy of activation is higher, rate of reaction is slower and if it is
lower, the rate of reaction is faster.

11. Continue…
• The role of enzyme in biochemical reaction is to reduce the amount
of energy of activation such that the rate of reaction increases.
• During enzyme catalysis, active site of enzyme binds with substrate
molecules to form Enzyme-substrate (ES) complex. During this
binding some binding energy is released which is utilized to activate
the substrate (reactant) molecules to form product. Thus the
requirement of the amount of activation energy is decreased such
that rate of reaction increases. The amount of activation decrease is
equal to the amount of binding energy released during binding of
enzyme and substrate.

12. THEEND
Thank you