The following kinetic data were obtained for an enzyme in the absence of any inhibitor (1), and in the presence of two different inhibitors (2) and (3) at 5mM concentration. Assume [ET] is the same in each experiment[/B]
(1) (2) (3)
1 12 4.3 5.5
2 20 8 9
4 29 14 13
8 35 21 16
12 40 26 18
Graph these data as Lineweaver-Burk plots and use your graph to find answers to a and b
a. Determine Vmax & Km for the enzyme
b. Determine the type of inhibition and the KI for each inhibitor
1/Vmax = y-intercept, slope = km/Vmax
The Attempt at a Solution
See attached table*[/B]
This is a table of above plus the reciprocal of each one. It is from the answer key of the homework, however for 1/
From there, I made a graph, one for each of the inhibitors. X was the 1/
From there, I was unsure how to find the slope and y-intercept since the numbers are not clear cut. I used the formula 1/V = Km/Vmax X 1/
The answer key showed these equations:
1. 1/V = 63.1 (1/[S}) + 1.96 X 10^4
2. 1/V = 212.3 (1/
3. 1/V = 137.4 (1/
From here I calculated the Km and Vmax, but again was confused with units.
I also tried calculating the slope via the equation y2-y1/x2-x1 using two points, but was off compared to the answer key.
For part b. I worked with my knowledge of the different types of inhibitors to know which formula to use
Competitive : Km,app = Km(1 + I/KI)
Noncompetitive: 1/Vmax,app = 1/Vmax (1 + I/KI)
It was hard for me to know which numbers to plug in here as part a and the introduction to the problem were also confusing.
Thank you in advance for any help you can give!