Which of the following residues acts as a general-acid catalyst in aldolase but as a general-base catalyst in chymotrypsin?

Question

Quizplus · Accepted Answer

Histidine can act as either a general-acid or general-base catalyst depending on its position within the active site and the specific reaction being catalyzed. In aldolase, it acts as a general-acid catalyst, donating a proton to the carbonyl group of the substrate. In chymotrypsin, it acts as a general-base catalyst, abstracting a proton from a water molecule to generate a hydroxide ion, which then attacks the peptide bond of the substrate. None of the other residues listed have this dual catalytic behavior.

Which of the Following Residues Acts as a General-Acid Catalyst