Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 7

More Enzyme Kinetics. The galactose formed in Reaction 6-17 can be phosphorylated by the transfer of a phosphate group from ATP, a reaction catalyzed by the enzyme galactokinase:
(1)
Assume that you have isolated the galactokinase enzyme and have determined its kinetic parameters by varying the concentration of galactose in the presence of a constant, high (i.e., saturating)concentration of ATP. The double-reciprocal (Lineweaver-Burk)plot of the data is shown as Figure.
(a)What is the K m of galactokinase for galactose under these assay conditions What does K m tell us about the enzyme
(b)What is the V max of the enzyme under these assay conditions What does V max tell us about the enzyme
(c)Assume that you now repeat the experiment, but with the ATP concentration varied and galactose present at a constant, high concentration. Assuming that all other conditions are maintained as before, would you expect to get the same V max value as in part b Why or why not
(d)In the experiment described in part c, the K m value turned out to be very different from the value determined in part b. Can you explain why
Figure Double-Reciprocal Plot for the Enzyme Galactokinase.