You measure the kinetics of an enzyme E as a function
Question # 00141607
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Updated on: 11/27/2015 04:38 AM Due on: 11/01/2015
1. You measure the kinetics of an enzyme E as a function of [S] and plot the following Lineweaver-Burke plot.
a) The enzyme concentration is kept constant at 1?M (10 -6 M). From these data, determine vmax, KM, kcat and the
turnover for the enzyme. Justify your answer clearly.
b) Now you study enzyme inhibition by measuring the kinetics in the presence of 10 mM inhibitor A or B (in
separate experiments, of course). The Lineweaver-Burke plots are in the figure to the right.
From these data, determine the type of inhibition for A and for B.
Justify your answer.
c) Illustrate with a drawing how the inhibition works for each inhibitor.
d) Which of the two inhibitors is more effective at high substrate concentrations?
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7. Thymidylate synthase catalyzes the synthesis of thymidine. Glu 60, Cys 198 and Arg 218 are three residues at the
active site. The reaction mechanism is shown below.
a. Which mode of enzymatic catalysis is exemplified by each residue? Write the name and number of the
residue next to the type of catalysis.
b. Which of the following mutations is likely to
produce an active enzyme: Glu 60 Thr, Cys 198 Val, Arg 218Lys?
Explain your answer.
c. Fluorodeoxyurydilate monophosphate (FdUMP) is an irreversible inhibitor of this enzyme (used in
chemotherapy).
What is the difference between reversible and irreversible inhibition and how could you tell the difference
experimentally?
a) The enzyme concentration is kept constant at 1?M (10 -6 M). From these data, determine vmax, KM, kcat and the
turnover for the enzyme. Justify your answer clearly.
b) Now you study enzyme inhibition by measuring the kinetics in the presence of 10 mM inhibitor A or B (in
separate experiments, of course). The Lineweaver-Burke plots are in the figure to the right.
From these data, determine the type of inhibition for A and for B.
Justify your answer.
c) Illustrate with a drawing how the inhibition works for each inhibitor.
d) Which of the two inhibitors is more effective at high substrate concentrations?
1
7. Thymidylate synthase catalyzes the synthesis of thymidine. Glu 60, Cys 198 and Arg 218 are three residues at the
active site. The reaction mechanism is shown below.
a. Which mode of enzymatic catalysis is exemplified by each residue? Write the name and number of the
residue next to the type of catalysis.
b. Which of the following mutations is likely to
produce an active enzyme: Glu 60 Thr, Cys 198 Val, Arg 218Lys?
Explain your answer.
c. Fluorodeoxyurydilate monophosphate (FdUMP) is an irreversible inhibitor of this enzyme (used in
chemotherapy).
What is the difference between reversible and irreversible inhibition and how could you tell the difference
experimentally?
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