FCH 530 Homework 6
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MICHAELIS MENTEN KINETICS
You have recently discovered a new enzyme "homeworkase" which destroys your
homework assignments. In order to characterize this enzyme, you wish to determine the
Km and Vmax. To do so, you make up several different concentrations of substrate
(keeping the enzyme concentration constant) and run the reaction. You obtain the
following results;
[Substrate] (pages/liter)
reaction rate (pages/liter/min)
__________________________________________________________________
1.0 x 10-3
65
5.0 x 10-4
63
1.0 x 10-4
51
5.0 x 10-5
42
3.0 x 10-5
33
2.0 x 10-5
27
1.0 x 10-5
17
5.0 x 10-6
9.5
1.0 x 10-6
2.2
5.0 x 10-7
1.1
1. Is this data consistent with Michaelis Menten kinetics? (hint: the easiest way to
determine this is to plot [v] vs [S] and see if you get a saturable curve.
2. Determine the Vmax and Km for this enzyme using both the Lineweaver Burk
inversion and an Eadie-Hofstee plot.
3. Show the derivation for the Michaelis Menten equation from the following
reaction (where E+P can be converted back to ES):
Show all work and assumptions. What are the definitions for each item in this equation,
i.e., What are E, S, k1, etc.
4. What are the differences between competitive, noncompetitive, and uncompetitive
inhibition of an enzyme. How would graphs of these data differ (draw out some
examples) for each type of inhibition? What happens to vmax and KM for each
condition? How do the inhibitors interact with the enzyme in each of these 3
cases?
5. Define Ki for each of the types of inhibition.
6. What is the Arrenhius equation? What does it predict?
7. How do the following contribute to enzyme catalysis: Proximity and orientation
of the substrate? Strain or distortion?
8. Write out a plausible mechanism for an acid catalyzed keto-enol tautomerism.
9. Write out a plausible mechanism for a base catalyzed keto-enol tautomerism.
10. Write out a plausible mechanism for a Serine protease. What enzymes are
involved? What is the general acid catalyst? What is the general base catalyst?