Answer:
a. participate in proton transfer - His
b. acts as a nucleophile - Ser
Explanation:
Enzymes are regulated because they are proteins. They are categorize based on how they catalyze. Heat weakens and inactivates the enzymes because of non covalent interaction. His amino acid participate in proton transfer because it is able to act as an acid as well as a base while Ser amino acid can act as nucleophile.