enzyme kinetics Flashcards
1
Q
What is Vmax (2)
A
- Maximum rate of the reaction (Ms⁻¹)
- Depends on [E]o
2
Q
What is KM
A
Substrate concentration at 1/2 Vmax
3
Q
What is [E]o (2)
A
- The total enzyme concentration
- [E] + [ES] + [Ep] + any other intermediate complexes
4
Q
What is v (2)
A
- The initial rate (Ms⁻¹)
- Recorded when substrate concentration is greater than the total enzyme concentration ([S] > [E]o)
5
Q
What is steady rate kinetics (3)
A
- when the concentration of intermediates, including the
enzyme-substrate complex (ES), remains constant. - During steady-state, [P] increases linearly with time.
- v (initial rate) = steady-state gradient of [P] versus time.
6
Q
What happens with saturation kinetics (3)
A
- Each plot is determined from a gradient of a graph of [P] vs t
- Curved because there is a limited supply of enzymes available
- Active sites become saturated at high [S]
7
Q
What is the Michaelis-Menten (MM) equation (3)
A
- v = Vmax[S] / KM + [S]
- KS = [E][S]/[ES]
- KM = [E][S]/ sum of [ES]
8
Q
What suggests strong and weak binding (2)
A
- Strong = low KS/KM
- Weak = high KS/KM
9
Q
What does v depend on
A
[S] and [E]o
10
Q
What is the catalytic constant (3)
A
- kcat (s⁻¹)
- The maximum number of substrate molecules converted to product per active site per unit time
- Vmax = kcat[E]o
11
Q
What are the two options to find KM and Vmax (3)
A
- Non-linear least-square analysis:
KM and Vmax are modelled by the computer until best-fit between data and the MM equation is obtained - Linear analysis: Lineweaver-Burk plots - Inferior but still common as no computer is required.
- Once Vmax is known, divide by [E]0 to obtain kcat.
12
Q
How is Vmax and KM determined from Lineweaver-Burk plots (2)
A
- Vmax = 1/y-intercept
- KM = -1/x-intercept
13
Q
How do you calculate the rate (v)
A
v = Vmax (Ms⁻¹) [S] / KM (M) + [S]
14
Q
How do you calculate substrate concentration (KM)
A
KM = [E][S] / Σ[ES]
15
Q
How do you calculate Vmax
A
Vmax = kcat [E]o
