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INHIBITION
Inhibitor: a substance that reduces the rate of an enzymecatalyzed reaction.
Activator: a substance that increases the rate of an
enzyme-catalyzed reaction.
Inhibitor
irreversible
reversible
linear
(complete inhibition)
hyperbolic
(partial inhibition)
Llinear inhibitor
competitive inhibition
uncompetitive inhibition
mixed inhibition
pure non competitiva inhibition
Reversible linear inhibition
Reversible inhibitors are substances that form dynamic
complexes with the enzyme
If the enzyme has no catalytic activity at all when saturated
with inhibitor the inhibitior is complete or linear in reference
to the straight line plots of the apparent values of 1/V or
Km/V against [I ]
Linear inhibition is classified according to the effect according
to the particular apparent Michaelis-Menten parameters that
are affected.
1) Competitive (or specific) inhibition:
affects V/Km and Km but not V
A competitive inhibitor is a substance that combines with
free enzyme in a manner that prevents substrate binding
acido succinic acid
acido fumaric acid

E  S
 ES
Km

I
 K i
EI
k2

 EP
Malonic acid
v  k2[ ES ]
E0  E ES  EI 
v
k 2 [ ES ]

E 0 E   ES   EI 

E S 
Km 
ES 

E S 
[ ES ] 
Km

E I 
Ki 
EI 

E I 
EI  
Ki
[ E ][ S ]
k2
Km
v

E 0 E   [ E ][ S ]  E I 
Km
Ki
k2 E 0 [ S ]
k2 E 0 [ S ]
v

K m I 
Km 
 [ S ] K m 1  I    [ S ]
 K 
Ki
i 

V S 
v
S   K mapp
app
V app  V
 I  
K  K m 1  
 Ki 
V app
V

K mapp
 I  
K m 1  
 Ki 
app
m
1 K mapp 1


v V S  V
Km

V
 I   1 1
1  

 K i  S  V
Slope 
app
Km
V

Km 


I
1 


V 
K i 
K
app
m
 I  
 K m 1  
 Ki 