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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 LibreTexts

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
Drop Your Choice Here 1. Acid-base catalysis
Drop Your Choice Here 2. Metal Ion and Electrostatic Catalysis
Drop Your Choice Here 3. ATP Hydrolysis
Drop Your Choice Here 4. Bond Strain or Distortion

Drag one of the choices below:

  • A. Transfer of a proton improves the departure of an unstable leaving group.
  • B. A charged ion stabilizes areas with too many electrons during a reaction step.
  • C. The molecular arrangement of the substrate is structurally destabilized.
  • D. A high energy molecule is broken down to drive conformational shifts.
 

True/False Statements About Enzyme Catalytic Strategies

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Which one of the following statements is FALSE about 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 TRUE about the enzyme function of Chymotrypsin?

 

True/False Statements About Enzyme Inhibitors

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Which one of the following statements is FALSE about enzyme inhibitors?

 

Enzyme Catalysis Mechanisms from Definitions

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Which one of the following mechanisms of enzyme catalysis correspond to the definition 'The spatial arrangement of atoms influences ionization and electron flow.'.

 

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+—Cys—Lys—Ser—Arg—Ser—Cys—Leu—Ala—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 E4 E5 E6
D → E → F → 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 D into product E.

The end product J of this pathway binds to enzyme 1and its substrate in the active site at the same time.
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  33.4  0.1 
0.002  50.0  0.2 
0.005  71.5  0.5 
0.010  83.4  1.0 
0.020  91.0  2.0 
0.050  96.2  4.8 
0.100  98.1  9.1 
0.200  99.1  16.7 
0.500  99.7  33.4 
1.000  99.9  50.0 
2.000  100.0  66.7 

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]).