Enzyme Inhibitors

Question 1

What are reversible inhibitors?

Answer 1

Molecules that bind and dissociate from the enzyme

Question 2

What are irreversible inhibitors?

Answer 2

Molecules that bind tightly to the enzyme to form a permanent complex

Question 3

What are the types of bonds formed for reversible and irreversible inhibitors?

Answer 3

Reversible:
- Hydrogen, electrostatic, hydrophobic, Van der Waals ( all are considered weak)

Irreversible:
- Covalent (strong)

Question 4

What are the types of reversible inhibitors

Answer 4

Competitive and non-competitive inhibitors

Question 5

What are the characteristics of competitive inhibitors?

Answer 5

• Interferes with the active site of the enzyme
• Substrate cannot bind
• Reduces enzyme activity
• Eventually, substrate would be able to bind to the enzyme
• Vmax is the same as the normal enzyme but Km is larger

Question 6

What are the characteristics of non-competitive inhibitors?

Answer 6

• Binds to the allosteric site
• Forms an enzyme-inhibitor complex
• Altering the globular shape of the enzyme (temporarily)
• Active site changes, substrate cannot bind to the active site, no products formed
• Vmax is lower than normal enzyme but Km is the same

Question 7

For competitive inhibitors, why is the rate of reaction slower when the inhibitors are added, but the reaction is still able to reach the same maximum rate as a normal enzyme?

Answer 7

The rate of reaction is slower as the competitive inhibitor is competing with the substrate for the active site
The reaction is still able to reach the same maximum rate as a normal enzyme as the substrate will eventually bind to the active site

Question 8

For non-competitive inhibitors, the substrate and inhibitor are not competing for the same site, so why is the reaction’s Vmax lower compared to a normal enzyme

Answer 8

Since the non-competitive inhibitor will bind to the allosteric site, it will change the shape of the enzyme temporarily
Therefore, the enzyme would not be able to work efficiently

Question 9

What are the characteristics of irreversible inhibitors?

Answer 9

• Bind to the enzymes covalently
• Inactivating the enzymes irreversibly/permanently
• React with some functional group in the active site, blocking the site