Enzyme kinetic problems
1. You measure the initial rate of an enzyme reaction as a function of substrate concentration in the presence and absence of an inhibitor. The following data was obtained:
|
[S]
(mM)
|
Vo (-) Inhibitor
(mM/min)
|
Vo (+) Inhibitor
(mM/min)
|
|
0.0001
|
33
|
17
|
|
0.0002
|
50
|
29
|
|
0.0005
|
71
|
50
|
|
0.001
|
83
|
67
|
|
0.002
|
91
|
80
|
Please submit calculations and graph for full credit!
Note: You are required to use Excel to generate the Lineweaver-Burk plot
(a) Create a Lineweaver-Burk plot (inhibited and uninhibited should be on the same plot!)
(b) Calculate the Vmax in the presence and absence of the inhibitor. Show your calculation.
(c) Calculate the Km in the presence and absence of the inhibitor. Show your calculation
(d) What type of inhibitor is this? How do you know (clearly explain)?
2. Prostaglandins are derivatives of fatty acids that are responsible for producing fever, inflammation and its associated pain. They are synthesized from a 20 carbon fatty acid, arachidonic acid (AA), in a reaction catalyzed by prostaglandin endoperoxide synthase. The product of the reaction, PGG2, can then be used to synthesize other prostaglandins. Ibuprofen is an inhibitor of prostaglandin endoperoxide synthase, thus it used to relieve pain and inflammation.
The following data was generated in the laboratory:
|
Arachidonic Acid(mM)
|
Rate of formation of PGG2 (mM/min)
|
Rate of formation of PGG2 with 10 mg/ml ibuprofen(mM/min)
|
|
0.5
|
23.5
|
16.67
|
|
1.0
|
32.2
|
25.25
|
|
1.5
|
36.9
|
30.49
|
|
2.5
|
41.8
|
37.04
|
|
3.5
|
44.0
|
38.91
|
Please submit calculations and graph for full credit!
Note: You are required to use Excel to generate the Lineweaver-Burk plot
(a) Create a Lineweaver-Burk plot (inhibited and uninhibited should be on the same plot!)
(b) Calculate Vmax and Km in absence of the inhibitor. Show your calculations.
(c) Calculate the Vmax and Km in the presence of the inhibitor. Show your calculations. What type of inhibitor is ibuprofen? Briefly explain your answer.