Question

An experiment was performed to determine the effects of an inhibitor on the breakdown of glycogen by an enzyme. In an accompanying experiment, the inhibitor was added to the glycogen-enzyme suspension and reacted using the same experimental conditions. The data obtained from these experiments is tabulated below. Draw the Michaelis-Menten and Lineweaver-Burke plots of these data. Determine the form of inhibition observed from these results and explain your rationale for this form. Determine the values for K_m and V_max from these results.

Answer 1

Michaelis-Menten equation is:

V_o=   

Where Vmax is the maximum velocity and

Km is the substrate concentration [S] at which the reaction velocity reaches its half (see image)

60 Vmax 50 40 20 10 Km 0 0.5 5 25 3 3.5 [Sl

For this equation Vmax = 48 mM/min and Km = 0.55 mM

In presence of inhibitor, Vmax decreased to 42.4 mM/min as shown in fig

50 45 max 35 30 25 20 With Inhibitor 0.5Kİ1 1.5 2 2.5 3

LB plots for the reaction with or without inhibitor are given below

Inhibitor y 0.023x+0.016 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0 y-0.013x + 0.016 Control 0 0.5 1.5 2.5 1/1S]

As we can see in the figures Slope changes when the inhibitor is added to the reaction, but intercept do not change. Therefore the inhibition is competitive inhibition.