Concept #1: Inhibition Constant

Example #1: A) Consider the data in the chart below.  Which enzyme has the strongest binding affinity for its substrate?
B) Which enzyme has the strongest binding affinity for its inhibitor?

Concept #2: Inhibition Constant of Free Enzyme (E)

Practice: Use the data in the chart below to determine the answer to the following:

A) Rank the enzymes in order of their binding affinity to their substrate (strongest affinity → weakest affinity).

a) A → B → C. 

b) C → A → B. 

c) C → B → A. 

d) B → A → C.

B) Rank the enzymes in order of their binding affinity to the inhibitor (strongest affinity → weakest affinity).

a) A → B → C. 

b) B → C → A. 

c) C → B → A. 

d) B → A → C.

C) Which enzyme would you expect the inhibitor to affect the most? Why?

a) Enzyme A. 

b) Enzyme B. 

c) Enzyme C.

Concept #3: Inhibition Constant of ES-Complex

Practice: Calculate the Michaelis constant (Km) and the inhibition constant (K I) given the following information:

[E] = 20 mM. [S] = 15 mM. [ES] = 5 mM. [I] = 8 mM. [EI] = 2 mM.