Graphical Analysis of Enzyme Inhibition  Inhibition  of Enzyme Kinetics Go back
Michaelis-Menten (MM) Kinetics Competitive Inhibition Mixed Noncompetitive Inhibition Uncompetitive Inhibition
[E] + [S]
k1

k2
[ES]
k3
 
[E] + [P]
Assumptions and givens:
  • d[ES]/dt = 0 -- steady-state approximation
  • [P] = 0 -- at time zero
  • V = d[P]/dt = k3 [ES]
  • [Etotal] = [E] + [ES]
  • Vmax = k3 [Etotal]
  • KM = (k2+ k3)/k1 = [S]1/2
    where V = (1/2) Vmax
V / Vmax = [S] / ([S] + KM ) -- MM equation
[E] + [S]
+
[I]
kI k-I
[EI]
k1

k2
[ES]
k3
[E] + [P]
Assumptions and givens:
  • d[ES]/dt = 0 -- steady-state approximation
  • [P] = 0 -- at time zero
  • V = d[P]/dt = k3 [ESn]
  • [Etotal] = [E] + [ES] + [EI]
  • Vmax = k3 [Etotal]
  • KM = (k2+ k3)/k1
  • KMapp = KM ( 1 + [I] / KI ) = ([S]1/2) where V = (1/2) Vmax
V / Vmax = [S] / ([S] + KMapp )
[E] + [S]
  +
  [I]
kI k-I
[EI]
k1

k2
[ES]
+
[I]
kI k-I
[ESI]
k3
[E] + [P]
Assumptions and givens:
  • d[ES]/dt = 0 -- steady-state approximation
  • [P] = 0 -- at time zero
  • V = d[P]/dt = k3 [ESn]
  • [Etotal] = [E] + [ES] + [EI] + [ESI]
  • Vmax = k3 [Etotal]
  • Vmaxapp = Vmax / ( 1 + [I] / KI )
  • KM = (k2+ k3)/k1 = ([S]1/2)
    where V = (1/2) Vmaxapp
V / Vmaxapp = [S] / ([S] + KM )
[E] + [S]
k1

k2
[ES]
+
[I]
kI k-I
[ESI]
k3
[E] + [P]
Assumptions and givens:
  • d[ES]/dt = 0 -- steady-state approximation
  • [P] = 0 -- at time zero
  • V = d[P]/dt = k3 [ESn]
  • [Etotal] = [E] + [ES] + [ESI]
  • Vmax = k3 [Etotal]
  • Vmaxapp = Vmax / ( 1 + [I] / KI )
  • KM = (k2+ k3)/k1
  • KMapp = KM / ( 1 + [I] / KI ) = ([S]1/2) where V = (1/2) Vmaxapp
V / Vmaxapp = [S] / ([S] + KMapp )
 
© Duane W. Sears
Revised: October 07, 2010