Question

[S] UM 320 160 80.0 40.0 20.0 10.0 Volumol nk-1 S-1) 169 132 92.0 57.2 32.6 17.5

(b.) calculate K_M for the enzyme

(c) When the reactions in part (b) are repeated in the presence of 12 microm of an uncompetitive inhibitor, the y-intercept of the Lineweaver-Burk plot is 0.352 (micromol-1 ml s). Calculate K'I for this inhibitor.

Answer 1

Michaelis Menten equation is

v = Vmax / (1 + (Km/[S]))

Lineweaver burk plot is between 1/[S] on x-axis and 1/Vo on y-axis.

Equation of this graph is y = 0.5287x + 0.0043

According to this equation, slope = 0.5287 and intercept = 0.0043

Also, intercept = 1/Vmax = 0.0043

Vmax = 232.55 uM/min

Slope = Km/Vmax = 0.5287

So, Km = 0.5287 *Vmax = 0.5287 *232.55= 122.95 uM

Answer : Km = 122.95 uM

Vmax = 232.55 uM/min

In presence of inhibitor

Vapp = Vmax / (1 + [I]/Ki)

since intercept = 1/vapp = 0.352 hence apparent Vmax = 2.84 uM/min

putting the values 2.84 = 232.55 / (1 + [12 uM] / Ki)

on solving Ki = 0.148361