Assessment of enzyme activity under standard condition and plotted as a linear Lineweaver-Burk plot gives the green line (x). The red line (y) was most likely obtained by addition of which of the following to this enzyme assay?

A) allosteric activator
B) competitive inhibitor
C) double the amount of enzyme
D) half the amount of enzyme
E) noncompetitive inhibitor

Question

Assessment of enzyme activity under standard condition and plotted as a linear Lineweaver-Burk plot gives the green line (x) . The red line (y) was most likely obtained by addition of which of the following to this enzyme assay?

A) allosteric activator 
B) competitive inhibitor 
C) double the amount of enzyme 
D) half the amount of enzyme 
E) noncompetitive inhibitor

Quizplus · Accepted Answer

Competitive inhibitors bind enzyme at the catalytic site, thereby competing with substrate for binding in a dynamic equilibrium-like process. This type of inhibition is reversible by the addition of higher concentrations of substrate. With competitive inhibitors the maximum velocity (V_max) of the reaction is unchanged, while the apparent affinity of the substrate to the binding site is decreased. In other words, K_m, as defined by the substrate concentration required for half maximal activity, is increased. These changes are visible in Lineweaver-Burk plots where the Y-axis intercept is unchanged, while the X-axis intercept is closer to the Y-axis. This is indicative of a larger value for Km.

Assessment of Enzyme Activity Under Standard Condition and Plotted as a Linear