The Graph Shows the Rate of Catalysis Versus PH for an Enzyme-Catalyzed

Multiple Choice

The graph shows the rate of catalysis versus pH for an enzyme-catalyzed reaction.What conclusion can be made from the graph?

A) The enzyme is completely denatured by pHs greater than 8 or less than 5.
B) The substrate has four ionizable groups.
C) At pH 6.2 all ionizable groups in the active site are protonated.
D) The enzyme has an acidic and a basic amino acid in the active site.
E) The enzyme has only one protonatable residue in the active site.