Question

You have an inhibitor for an enzyme that you are studying.  The concentration of inhibitor used is 5.50 µM.  The following data was collected for the non-inhibited reaction as well as the reaction that was inhibited.

	mmol/(mL min)	mmol/(mL min)
mM Substrate	Vo Substrate	Vo + Inhibitor
0.200	5.000	3.751
0.400	7.500	4.998
0.800	10.000	5.995
1.000	10.700	6.173
2.000	12.500	6.807
4.000	13.600	7.143

a. Plot this data using Excel or a graphing program.  Make sure you give your graph has a title and the legends are labeled.  It is also good to have the trend line equation for each line on your graph.  Attach the graph to your homework for credit.

b. Determine Km and Vmax of the substrate in the non-inhibited reaction.

Km =  ________________

Vmax = ______________

c. Determine what type of inhibition occurs in this reaction.

d. Determine the apparent Km and apparent Vmax in the presence of the inhibitor.

Km^app= ___________________

Vmax^app= _________________

e. Determine the value of K_Ifor the inhibitor

K_I=  __________________

Answer 1

Ans. #a. See the graph.

#b. See the data table (left bottom, Blue-shaded)

#c. Note that the un-inhibited and inhibited kinetic lines parallel to each other. It indicates that both the Vmax(app) and Km(app) is decreased by the same factor in presence of the inhibitor. It is the characteristic of an un-competitive inhibitor. So, the given is an un-competitive inhibitor.

#d. See the data table (left bottom, light red-shaded)

#e.