Enzyme Kinematics + Inhibition

What are the 3 assumptions of enzymatic kinetics?

I. ) 1 subs —> 1 prod

II.) K2 —> Kcat is rate determining step (velocity dependent)

III.) Concentration of ES is constant

What is the steady-state assumption?

ES breakdown occurs at the same rate as ES formation

Michaelis-Menten Equation

Vo = Max [S]/Km + S

Lineweaver Burk Equation

1/Vo = (Km/Vmax)(1/[S]) + 1/VmaxW

What’s the y-intercept of Lineweaver equation?

1/Vmax

What’s the slope of Lineweaver equation?

(Km/Vmax)

What’s the x-intercept of Lineweaver equation?

-1/Km

What’s the x of Lineweaver equation?

1/[S]

Catalytic efficiency equation

Kcat/Km

Kcat is equivalent to

K2

Vmax =

Kcat * [Et]

Kcat = (equation)

Vmax/Et

If Km decreases… enzyme affinity

increases

If Km increases… enzyme affinity

decreases

Ki =

[I]/α-1

K’i=

[I]/α-1

Ki is

dissociation constant for how tightly the inhibitor binds to [E]

K’i is

dissociation constant for how tightly the inhibitor binds to [ES]

High Ki means

lower inhibitor affinity to enzyme

Low Ki means

higher inhibitor affinity to enzyme

High K’i means

low inhibitor affinity to [ES]

Low K’i means

high inhibitor affinity to [ES]