MBMB 451b

Copyright 2000, E.C. Niederhoffer

Sample Problem

The figure below shows the dependence of initial velocity, vo, on substrate concentration for an enzyme with a Michaelis constant equal to 3 x 10-4 M.

a. Calculate Vmax.

Choose a point from the graph. A convenient data pair (x,y) is (3 x 10-6, 2 x 10-6).

Remember the Michaelis-Menten equation:

but use the simplified form and use the following assumption given to you, [S] << Km.

So:

vo = (Vmax/Km)[S]

Vmax = voKm/[S] = 2 x 10-6 M min-1 (3 x 10-4 M)/3 x 10-6 M = 2 x 10-4 M min-1

b. Is this the proper data region for evaluating Vmax?

No, we're evaluating Vmax in the 1st-order region, far from enzyme saturation.

 

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