This applet requires you to systematically vary the apparent K_ms and V_maxs of an enzyme acting on a single substrate, subject to inhibition by an inhibitor, I, until a satisfactory fit to all experimental data is obtained. Click on the Start button in the applet to plot reaction velocity (V) against substrate concentration ([S]) [left hand graph panel] and to show their double reciprocals in a Lineweaver-Burk plot (1/V versus 1/[S]) [right graph panel]. Adjust the apparent K_ms and V_maxs of the enzyme until you are satisfied with the fit.

Apparent V_maxs are equal to the reciprocals of the intercepts on the 1/V axis of the lines in the right graph panel. Apparent K_ms are equal to the slopes of the lines divided by the corresponding intercepts on the 1/V axis of the lines in the right graph panel. The curves drawn through the data points in the left graph panel are obtained by substituting apparent V_maxs and corresponding apparent K_ms in the Michaelis-Menten equation:

The enzyme was assayed with different concentrations of substrate (S) at different inhibitor concentrations (I0 = 0 mM --- RED; I1 = 0.1 mM --- BLUE; I2 = 0.2 mM --- GREEN; I3 = 0.5 mM --- MAGENTA).

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After you have estimated K_ms and V_maxs, and have determined whether the inhibitor is uncompetitive, competitive or noncompetitive, enter your answers below, print the page and compare your answers with those determined by regression analysis.

Applet code.
Last update: 09/12/2002
Authors: David Rhodes