Suppose that an enzyme uses a catalytic mechanism in which a functional group on the enzyme has to accept a proton from the intermediate formed in the first chemical step. The pKa of that basic functional group on the enzyme is 8.0, and is the only pKa apparent on a plot of kcat vs pH for the activity of this enzyme. The kcat of the fully active form of the enzyme is 1 X 10 ^5 sec^-1.

1. What will a graph of the effect of pH on the activity of this enzyme look like? (Graph of kcat vs pH)

2. What type of functional group might be responsible for the pH effect on kcat? Justify your anser based on the generic pKa values of functional groups in peptides and proteins..