Question

The activity of an enzyme requires a glutamic acid to display its −COOH functional group in the protonated state. Suppose the pKa of the −COOH group is 4.07.

Part A Part complete
Will the enzyme be more active at pH 3.5 or 4.5?

Answer 1

The enzyme will be more active at pH 3.5 compared to pH 4.5 because this is below the pKa of the glutamic acid's −COOH group, ensuring that it remains in the required protonated state for enzyme activity.

Step-by-step explanation:

The enzyme in question will be more active at pH 3.5 than at pH 4.5, given that the pKa of the glutamic acid's −COOH group is 4.07. Enzymatic activity is closely linked to the pH of the environment due to the ionization state of the functional groups involved in the catalysis process. At a pH lower than the pKa, glutamic acid's carboxyl group (−COOH) tends to be protonated, which is the required state for enzyme activity as indicated in the question. Conversely, at a pH higher than the pKa, the carboxyl group is more likely to lose a proton and become deprotonated, rendering the enzyme less active.

Enzyme activity is often highly sensitive to changes in pH. Even slight deviations from the optimal pH can alter the charge state of amino acid residues in the active site necessary for substrate binding and activity. Hence, an enzyme's catalytic activity is generally highest within a narrow pH range suited to the proper charge of its ionizable side groups.