An enzyme attracts substrates to its active site, catalyzes the chemical reaction by which products are formed, and then allows the products to dissociate (separate from the enzyme surface). The combination formed by an enzyme and its substrates is called the enzyme–substrate complex.

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.