8: Enzyme Inhibition
Students classify inhibition type (competitive, noncompetitive, uncompetitive, mixed) from changes in Km and Vmax in Michaelis-Menten data, and interpret inhibitor effects on Lineweaver-Burk plots.
LibreTexts reference: Unit 2, Chapter 3: Enzyme Inhibition 
Matching Enzyme Catalytic Mechanisms to Definitions
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Match each of the following mechanisms of enzyme catalysis with their corresponding definitions.
Note: Each choice will be used exactly once.
| Your Choice | Prompt | |
|---|---|---|
| 1. Covalent Catalysis | ||
| 2. Bond Strain or Distortion | ||
| 3. Catalysis by Approximation | ||
| 4. Acid-base catalysis |
Drag one of the choices below:
- A. Mechanical stress is applied to stretch or compress bonds in the substrate.
- B. A group adjusts the electron flow by altering local charge through hydrogen transfer.
- C. A short-lived connection forms between the substrate and the enzyme.
- D. The reaction site arranges substrate components to ensure correct position for reaction.
True/False Statements About Enzyme Catalytic Strategies
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Which one of the following statements is TRUE concerning Enzyme Catalytic Strategies and Methods for Lowering Activation Energy?
True/False Statements About Chymotrypsin Function
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Which one of the following statements is FALSE of the enzyme function of Chymotrypsin?
True/False Statements About Enzyme Inhibitors
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Which one of the following statements is FALSE regarding enzyme inhibitors?
Enzyme Catalysis Mechanisms from Definitions
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Which one of the following mechanisms of enzyme catalysis correspond to the definition 'Local concentration of substrates is effectively increased by spatial confinement.'.
Cleavage Sites for Chymotrypsin Digestion of Peptides
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Your professor provides your group with a peptide that will be the focus of your next enzymatic digestion experiment. Before performing the reaction, you are asked to predict where cleavage is most likely to occur under the planned conditions.
The peptide sequence is:
NH3+—Ala—Lys—Thr—Lys—Gln—Tyr—Asp—Gln—Cys—COO–
You will be incubating the peptide with chymotrypsin in a buffered solution at physiological pH. Following digestion, you will analyze the products using mass spectrometry.
Which peptide bond will most likely to be cleaved during the incubation?
Enzyme Inhibition Type from Metabolic Pathway Descriptions (BCHM 355)
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A series of enzymes catalyze the reactions in the following metabolic pathway:
| E1 | E2 | E3 | ||||
| G | → | H | → | I | → | J |
Understanding the type of enzyme inhibition or activation is crucial for developing effective drugs and understanding metabolic regulation.
enzyme 1 converts substrate G into product H.The end product J of this pathway binds to enzyme 1at a location far away from its active site.
This binding decreases the activity of the enzyme.
Determine the type of enzyme inhibition or activation described:
Enzyme Inhibition Type from Enzyme Activity Data
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Michaelis-Menten Kinetics and Inhibition Type Determination
The table below presents data on enzyme activity measured as initial reaction velocities (V0) with and without the presence of an inhibitor at various substrate concentrations ([S]).
| substrate concentration, [S] |
initial reaction velocity no inhibitor V0 (–inh) |
initial reaction velocity with inhibitor V0 (+inh) |
|---|---|---|
| 0.001 | 13.4 | 13.4 |
| 0.002 | 22.9 | 20.0 |
| 0.005 | 40.0 | 28.6 |
| 0.010 | 53.4 | 33.4 |
| 0.020 | 64.0 | 36.4 |
| 0.050 | 72.8 | 38.5 |
| 0.100 | 76.2 | 39.3 |
| 0.200 | 78.1 | 39.7 |
| 0.500 | 79.3 | 39.9 |
| 1.000 | 79.7 | 40.0 |
| 2.000 | 79.9 | 40.0 |
| 5.000 | 80.0 | 40.0 |
Based on the data provided, determine the type of inhibition show by the inhibitor. Consider how the addition of the inhibitor affects the initial reaction velocities (V0) at various substrate concentrations ([S]).