Enzyme Inhibition

Question 1

What is a Lineweaver Burke plot and what information does it tell you?

Answer 1

• Gives an accurate measurement of Km and Vmax
• x-int: -1/Km
• y-int: 1/Vmax

Question 2

Competitive Inhibitors

Answer 2

• Competes with substrate for substrate binding site on enzyme
• KI = inhibition constant (works the same as Km)
• High affinity interactions are key

Question 3

How do you make a good competative inhibitor?

Answer 3

• Enzymes preferentially bind to the transition state
• Design a molecule that looks like the transition state of an enzyme

Question 4

How do competative inhibitors affect Km / Vmax?

Answer 4

• Equilibrium shifts to the left
• Km (apparent) increases
• More substrate is needed to fill up 1/2 of substrate active sites
• Vmax is unaffected (competitive inhibitors only compete with the substrate for the active site. At a high enough concentration the substrate can out-compete the inhibitor and reach Vmax)

Question 5

Non-competative inhibitors

Answer 5

• Bind to a site away from the active site of the enzyme
• Not directly competing with substrate
• Allosteric effects allow non-competative inhibitors to effect catalysis
• Km will not be affected (does not interfere with an enzymes ability to bind to its substrate)
• Vmax will decrease

Question 6

Mixed Inhibitors

Answer 6

• Capable of binding to both free enzyme and enzyme substrate complex
• Vmax will decrease
• Km will vary depending on if the inhibitor is bound more tightly to free enzyme or enzyme substrate complex

Question 7

Uncompetitive Inhibitors

Answer 7

• Do not bind to free enzyme
• Only binds to enzyme substrate complex
• Vmax will decrease
• Km apparent will decrease (the inhibitor stabilizes the enzyme substrate complex making it easier for the enzyme to bind to the substrate increasing the apparent affinity of the enzyme for the substrate)