This applet demonstrates noncompetitive inhibition of an enzyme acting on a single substrate. Click on the Start button to plot reaction velocity (V) against substrate concentration (S) [left hand graph panel] and to show the corresponding Eadie-Hofstee plots (V/[S] versus V) [right graph panel].

Apparent V_maxs are equal to the intercepts on the V/[S] axis divided by the negative of the slopes of the regression lines in the right graph panel. Apparent K_ms are equal to the negative of the slopes of the regression lines in the right graph panel. The curves drawn through the data points in the left graph panel are obtained by substituting V_maxs and corresponding K_ms in the Michaelis-Menten equation:

Colors refer to different inhibitor concentrations (I0 = 0 mM --- BLACK; I1 = 0.1 mM --- RED; I2 = 0.2 mM --- BLUE; I3 = 0.5 mM --- MAGENTA).

Note that with the default values of [S] and V provided, the apparent K_m values remain fairly constant as [I] increases, and the apparent V_max values decrease markedly as [I] increases. This shows that the inhibitor, I, is a "noncompetitive" inhibitor. This type of inhibition is distinguished from "competitive" inhibition, which alters only apparent K_m, and from "uncompetitive" inhibition which alters both apparent K_m and apparent V_max.