1.
S U B M I T T E D T O : S I R A S I F S H A H Z A D
S U B M I T T E D B Y : I S H W A B A B A R
D E P A R T M E N T O F B I O C H E M I S T R Y
L Y A L L P U R I N S T I T U T E O F M A N A G E M E N T &
S C I E N C E
MECHANISM OF ENZYME
ACTION

2.
Contents:
 Introduction to Enzyme
 Active Site
 Apoenzyme & Holoenzyme
 Cofactor & Types
 Mechanism of Enzyme Action:
 Lock and Key Model
 Induced and Fit Model

3.
Introduction of Enzyme
“Enzyme can be defined as are
biological catalysts that speed up
the rate of the biochemical
reactions.”
For Example:
The enzyme amylase, which is
present in saliva, converts starch
into sugar, helping to initiate
digestion.
In medicine, the enzyme
thrombin is used to promote
wound healing.

4.
Active Site
 Enzyme molecules contain a special pocket called
the active sites.

5.
Apoenzyme & Holoenzyme
 The enzyme without its non protein moiety is termed
as apoenzyme and it is inactive.
 Holoezyme is an active enzyme with its non protein
component.

6.
Important Terms
 Cofactor: A cofactor is a non protein chemical compound that
is bound (either tightly or loosely) to an enzyme and is required
for catalysis.
 Types of Cofactors:
 Coenymes
 Prosthetic Groups
 Coenzyme: The non protein component, loosely bound to
apoenzyme by non covalent bond.
 Example: vitamins or compound derived from vitamins.
 Prosthetic Group: The non protein component, tightly
bound to the apoenzyme by covalent bonds is called a
prosthetic group.

7.
Mechanism of Enzyme Action
 Formation of enzyme
substrate complex by:
 Lock and Key Model
 Induced Fit Model
 Lock and Key Model:
 Proposed by EMIL FISHER
in 1894
 Lock and key hypothesis assumes
the active site of an enzymes are
rigid in its shape.
 There is no change in the active
site before and after a chemical
reaction.

8.
Induced Fit Model
 More recent studies have
revealed that the process is
much more likely to involve
an induced fit model
proposed by DANIYSL KOSH
LAND in 1958
 According to this exposure of
an enzyme to substrate cause
a change in enzyme, which
cause the active site to change
its shape to allow enzyme and
substrate to bind.