The following data was obtained in three different sets ofexperiments utilizing an enzyme obeying the Michaelis-Menten rate law; the first set of experiments was performed in the absence of inhibitor, the second and third sets inthe presence of a 10 mM concentrations of two different inhibitors (I1 and I2). The total enzyme concentration was constant throughout.
vo (μMs-1)
[S] (mM) [I] = 0 [I1] =10 mM [I2]= 10 mM
1 2.5 1.17 0.77
2 4.0 2.10 1.25
5 6.3 4.00 2.00
10 7.6 5.7 2.50
20 9.0 7.2 2.86
a) Determine KM and Vmax for the enzyme. For each inhibitor,determine the type of inhibition as well as the constants Ki and/or Ki′. What additional piece of information is required to calculate the turnover number of the enzyme?
b) If [S] = 5 mM, calculate the fraction of enzyme molecules that have a bound substrate i) in the absence of inhibitor, ii) in the presence of 10mM I1, and iii) in the presence of 10 mM I2.