Enzyme Problems
Please show all work

1.  The following kinetic data were obtained for an enzyme-catalyzed reaction:

            [S] (mM)            Velocity (rate) M/min
                0.1                        3.33
                0.2                        5.00
                0.5                        7.14
                0.8                        8.00
                1.0                        8.33
                2.0                        9.09
 

a.  Plot the velocity (rate) of this reaction as a function of substrate concentration; draw the horizontal maximum rate line.

b.  Complete a Lineweaver-Burk plot of these data, determine KM and Vmax.

c.  The enzyme concentration was 1.0 x 10-6 M.  Calculate the turnover number and explain the physical significance of this number.
2. (Extra Credit)  The following kinetic data were obtained for an enzyme-catalyzed reaction in the presence and absence of inhibitor Y:

            [S] (mM)            Velocity (rate) M/min    Velocity (rate) M/min
                                        No Inhibitor Y                With Inhibitor Y
                0.2                          5.0                                    3.0
                0.4                          7.5                                    5.0
                0.8                        10.0                                    7.5
                1.0                        10.7                                    8.3
                2.0                        12.5                                  10.7
                4.0                        13.6                                  12.5
 

a.  Plot the velocity (rate) of this reaction as a function of substrate concentration for both the uninhibited and inhibited reaction; draw the horizontal maximum rate lines.

b.  Outline the specific underlying reason why the inhibited rates of reaction are slower by discussing how Y interacts with E or with the ES complex.

c.  Do Lineweaver-Burk plots of these two sets of data, determine KM and Vmax for each,

d.  For inhibited reactions, KM is increased by a factor of (1 + [I]/Ki), where [I] is the inhibitor concentration and Ki is the inhibitor dissociation constant.  Assuming the inhibitor concentration [I] was 0.2 mM in these experiments, uses the Lineweaver-Burk slope data and calculated KM 's for uninhibited and inhibited reactions to determine the Ki inhibitor dissociation equilibrium constant.