Question

(15 points) The following data is for a reaction catalyzed by tyrosine monoxygenase:

Substrate Concentration (mol/L)                Initial Velocity (mM/min)

1.5                                                                   0.66

1.2                                                                   0.65

0.81                                                                 0.45

0.65                                                                 0.39

0.49                                                                 0.32

0.27                                                                 0.21

a) Plot the velocity (y-axis) versus substrate concentration [S] (x-axis) curve and insert/draw the graph in the space below. What are the approximate K_M and V_max values?

b) Construct a 1/v (y-axis) versus 1/[S] (x-axis) plot in the space below. Calculate the K_M and V_max values.

c) Calculate the initial velocity if the substrate concentration is 0.74 mol/L.

Answer 1

a) From the graph of Velocity vs Substrate concentration, we have the following conclusions:

1) If the amount of the enzyme is kept constant and the substrate concentration is then gradually increased, the reaction velocity will increase until it reaches a maximum. After this point, increases in substrate concentration will not increase the velocity.

2) KM (Michaelis constant) is the substrate concentration at half the maximum velocity.

From the graph given below VMax = 0.66

Vmax/2 = 0.33

KM = 0.51

-0:8- Vmax -0:6 0:4 Vmax/2 0-2 KM

b) The graph of 1/v vs 1/S has the following points: (0.67, 1.51), (0.83, 1.54), (1.23, 2.22), (1.53, 2.56), (2.04, 3.13), (3.7,4.76)

The graph is given below

c) From the first graph, when S= 0.74, we get initial velocity is 0.42 mM/min