1. Assume that you can measure the effects of identical concentration of two inh
ID: 495412 • Letter: 1
Question
1. Assume that you can measure the effects of identical concentration of two inhibitors x and Z, on the K and V M and Vmax of an Enzyme. Which of the following would be consistent with inhibitor X being a more effective inhibitor than Z?
2. Explain why an answer is either wrong/right.
a. Inhibitor X increases KM less than inhibitor Z while neither has an effect on V Max.
b. Inhibitor X decreases KM and VMax two-fold while inhibitor Z decreases both three-fold.
c. Inhibitor X doubles the KM and it decreases VMax by 50% while inhibitor Z triples the KM and it decreases the VMax by 40%.
d. Inhibitor X doubles the KM and it decreases VMax by 50% while inhibitor Z triples the KM and it decreases VMax by 10%.
PLEASE EXPLAIN THOROUGHLY!!!!!!!!!!!!!!!!!
Explanation / Answer
1 / V = Km / (Vmax [S]) + 1 / Vmax … eqn(1)
For a more effective inhibitor, the reaction rate (V) should be minimum.
2
a)
From equation 1
As Km increases, V decreases for the same Vmax. For a more effective inhibitor Km should increase more. Inhibitor Z is more effective.
b)
From equation 1
For the same ratio of Km and Vmax, lower the value of Vmax lower will be the reaction rate V.
Inhibitor Z decreases Vmax three fold. Z is more effective.
c)
Inhibitor X : Km/Vmax = 2/0.5 = 4. Vmax = Vmax * 0.5
Inhibitor Z : Km/Vmax = 3/0.6 = 5. Vmax = Vmax * 0.6
Not much difference between Vmax by inhibitors X & Z.
Greater the ratio of Km/Vmax better the inhibitor.
Inhibitor Z is more effective.
d)
Inhibitor X : Km/Vmax = 2/0.5 = 4. Vmax = Vmax * 0.5
Inhibitor Z : Km/Vmax = 3/0.9 = 3.3. Vmax = Vmax * 0.9
Lower the Vmax better the inhibitor.
Greater the ratio of Km/Vmax better the inhibitor.
Both conditions are satisfied by inhibitor X.
Inhibitor X is more effective.
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