Lecture 2. Basic Enzyme Kinetics Flashcards
What conditions do study-state studies involve and why?
[S] > > [E] so that v can be measured over a reasonable period
What does v represent?
The steady-state rate of reaction
Within the steady-state what is v proportional to?
[E]
What is the relationship between v and [S] at low [S] and [E] is constant?
v is proportional to [S]
What is the relationship between v and [S] at high [S] and [E] is constant?
v becomes constant
When enzyme becomes saturated at high [S], what is rate?
Vmax
Enzyme, substrate and product model
E + S ⇌ ES → E + P
What does ka represent?
E + S → ES
What does kd represent?
ES → E + S
Dissociation constant equation
K = [E][S]/[ES] = kd/ka
What in most cases the slowest step in the model?
ES → E + P
What is the Michaelis-Menten equation?
v = (Vmax x [S])/(Km + [S])
What is the value of Km when v equals half of Vmax?
Km = [S]
What is Vmax?
The maximum velocity and shows how fast the enzyme can work
What is Km?
The Michaelis constant
What is Km a measure of?
Affinity and shows the [S] range over which the enzyme works
What is enzyme efficiency represented as?
kcat/Km
What are the units for enzyme efficiency?
s⁻¹M⁻¹
Does Vmax vary with [E]?
Yes
What happens to Km and Vmax when one enzyme accepts two different substrates under identical conditions and [E] is the same?
Vmax stays the same but Km may vary
What are the axes for the Lineweaver-Burk plot?
x axis = 1/[S]
y axis = 1/v
On a Lineweaver-Burk plot, what does the y-intercept represent?
1/Vmax
On a Lineweaver-Burk plot, what does the x-intercept represent?
-1/Km
On a Lineweaver-Burk plot, what does the gradient represent?
Km/Vmax
