Concept #1: Competitive Inhibition

Concept #2: Competitive Inhibitor Effects

Concept #3: Competitive Inhibition & Michaelis-Menten-Plots

Concept #4: Competitive Inhibition & Lineweaver-Burk-Plots

Practice: Which of the following would be altered on a Lineweaver-Burk plot in the presence of a competitive inhibitor?

Practice: N-hydroxy-L-arginine (an intermediate in nitric oxide biosynthesis) can bind to the active site of arginase making its manganese reactive metal center unavailable for catalysis. How would an increased concentration of this intermediate be expected to affect the kinetic parameters of this enzyme?

Practice: An enzyme has a Km of 8 ฮผM in the absence of a competitive inhibitor and a K ๐ฆ๐š๐ฉ๐ฉ of 12 ฮผM in the presence of 3 ฮผM of the inhibitor. Calculate the KI.

Practice: Use the Lineweaver-Burk plot below to answer the following questions. Units of [S] are in nM.

A) Estimate the values of Km & Vmax as well as the K๐ฆ๐š๐ฉ๐ฉ & V๐ฆ๐š๐ฑ๐š๐ฉ๐ฉ for the reactions in the absence and presence of the competitive inhibitor.

B) Would you expect the competitive inhibitor to be more effective under conditions of high or low [S]? Why?

C) If [I] = 10 nM, calculate the inhibition constant (K I).