Concept #1: Apparent Km and Vmax

Concept #2: Kmapp and Vmaxapp Are Affected by α And/Or α’

Example #1: The KI value for a certain competitive inhibitor is 2 µM.  When no inhibitor is present, the Km value is 10 µM.  Calculate the apparent Km when 4 µM inhibitor is present.

Practice: Competitive inhibitor A at a concentration of 2 μM doubles the apparent K m for an enzymatic reaction, whereas competitive inhibitor B at a concentration of 9 μM quadruples the apparent Km. What is the ratio of the K I for inhibitor B to the K I for inhibitor A?

Practice: The KI value for a certain competitive inhibitor is 10 mM. When no inhibitor is present, the Km value is 50 mM. Calculate the apparent Km when 40 mM inhibitor is present.

Practice: Uncompetitive inhibitor A at a concentration of 4 mM cuts the K mapp in half for an enzymatic reaction, whereas the Kmapp is one-fourth the Km in the presence of 18 mM uncompetitive inhibitor B. What is the ratio of the K’I for inhibitor A to the K’I for inhibitor B?