In: Biology
The following kinetic data were obtained for an enzyme in the absence of inhibitor (1), and in the presence of an inhibitor at 5 mM concentration (2). Assume[ET] is the same in each experiment. [S] (mM) (1) v(µmol/mL sec) (2) v(µmol/mL sec) 1 12 4.3 2 20 8 4 29 14 8 35 21 12 40 26
[S] (mM) |
(1) v(µmol/mL sec) |
(2) v(µmol/mL sec) |
1 |
12 |
4.3 |
2 |
20 |
8 |
4 |
29 |
14 |
8 |
35 |
21 |
12 |
40 |
26 |
a. Using a graphing program (excel or sigmaplot) construct a Lineweaver burke plot representing the uninhibited reaction and the inhibited reaction on the same plot (to submit your graphs please paste into either a word or a pdf document along with your solutions)
b. What is the equation for each of the lines? (on the graph)
c. Determine Vmax and Km for the enzyme.
d. Determine the type of inhibition and the KI for the inhibitor.
Accoring to the Lineweaver Berk equation-
The y- axis is 1/v (1/rate) and x axis is 1/s (1/substrate)
Best-fit values | 1 (without inhibitor) | 2 (with inhibitor) |
Slope | 0.06314 ± 0.001473 | 0.2117 ± 0.001806 |
Y-intercept when X=0.0 | 0.01955 ± 0.0007614 | 0.02008 ± 0.0009332 |
X-intercept when Y=0.0 | -0.3096 | -0.09487 |
b) Equation of curve without inhibitor (v1)-
y= 0.06314x + 0.01955
Equation of curve with inhibitor (v2)-
y= 0.2117x + 0.02008
c) For 1- Without inhibitor-
Y-intercept= 1/Vmax = 0.01955
Thus Vmax= 1/0.01955 = 51.15 µmol/mL sec
X-intercept= -1/Km = -0.3096
Km= 3.23mM
For 2- With inhibitor-
Y-intercept= 1/Vmax = 0.02008
Thus Vmax= 1/0.02008 = 49.8 µmol/mL sec
X-intercept= -1/Km = -0.09487
Km= 10.54mM
d) Since the Vmax with inhibitor is lower than without inhibitor and the Km with inhibitor is more than Km without inhibitor, thus the type of inhibition is- Mixed inhibition