Problem Set 8
1. Draw two plots (A and B together, then A and C together) that
show how an enzyme-catalyzed reaction rate (velocity) varies with substrate
concentration. For Case A, there is no inhibitor present. For Case B, there is
a competitive inhibitor present. For Case C, there is a noncompetitive
inhibitor present. Be sure to show the KM and the Vmax for each of the three cases on the two plots.
Clearly describe the difference between competitive and noncompetitive
inhibitors.
2. Examination of a receptor interaction study of three drugs
undergoing clinical trials revealed Kd’s
of 40 nM, 2 mM, and 900 pM for
Drugs A, B, and C respectively. Drug A was found to
have greatest efficacy, while Drug B was found to have the lowest efficacy.
a. Draw a dose-response plot
that illustrates the curves for drugs A, B and C.
b. Clearly define what is specifically meant by a drug’s
efficacy and potency
c. Describe the relative potency and efficacy for drugs A, B, and C;
clearly support your answer.
d. Compare the relative affinities of the three drugs for the
receptor binding site and clearly support your answer.
3. The KM for an enzyme catalyzed reaction at a
temperature of 310K was found to be 10 mM. Determine
the substrate concentration at which 80% of the enzyme molecules have their
active sites occupied by the substrate.
4. A recent enzyme-catalyzed reaction study revealed the following
reaction rates for various substrate concentrations. An enzyme concentration of
10 mM was used for
all runs. Using the data listed in the table below, answer each of these
questions:
[S] mM |
Velocity (M/min) |
0.10 |
3.33 |
0.20 |
5 |
0.50 |
7.14 |
0.80 |
8 |
1.00 |
8.33 |
2.00 |
9.09 |
a. Construct a Lineweaver-Burk plot of
these data; show both the data and the plot.
b. Do a linear fit to these data; determine the slope and intercept.
c. Determine KM and Vmax
d. Determine the turnover number for the enzyme used in this
reaction.