How does the value of Vmax compare to Vmax app for the inhibited enzyme for: com
ID: 902774 • Letter: H
Question
How does the value of Vmax compare to Vmax app for the inhibited enzyme for: competitive inhibition uncompetitive inhibition noncompetitive inhibition How does the value of Km compare to Km app for the inhibited enzyme for: competitive inhibition uncompetitive inhibition noncompetitive inhibition For each of the graphs above, draw a line that reflects a better inhibitor than the one depicted. How would diisopropylphosphofluoridate (DIPF, irreversible inhibitor) affect the apparent Km and Vmax of a sample of chymotrypsin?Explanation / Answer
1.
a. Vmax = Vmax,inh
b. 1/Vmax < 1/Vmax,inh so Vmax > Vmax,inh
c. 1/Vmax < 1/Vmax,inh so Vmax > Vmax,inh
2. What you see on abscissa at left are the negative value of 1/Km.
Put them in symetrical positions on the right part of abscissa.
a. 1/Km > 1/Km,inh so Km < Km,inh
b. 1/Km < 1/Km,inh so Km>Km,inh
c. 1/Km > 1/Km,inh so Km < Km,inh
3.
“Competitive” graph: draw a new line with a higher slope passing by the same intersecting point of the existing ones (it will have the same 1/Vmax).
“Uncompetitive” graph: draw a new parallel line above the existing one (+Inh).It will have the highest 1/Vmax).
“mixed” graph: draw a new line with a higher slope passing by the same intersecting point of the existing ones (it will have the highest 1/Vmax).
These are Lineweaver-Burke plots ( more theory here http://chemwiki.ucdavis.edu/Biological_Chemistry/Catalysts/Enzymatic_Kinetics/Enzyme_Inhibition )
Note:
At questions 1,2 and 3 the inhibition is reversible.
4. If the inhibition is irreversible (DIPF is of this type) : Km remains the same, but Vmax is decreased by the presence of inhibitor (the concentration of Inh being lower than the enzyme concentration; if [DIPF] > [Chymotrypsine] , the activity is completely blocked).
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