Biochemistry Enzyme Kinetics b4ad0521 Which of the following enzymes is stable at acidic pH: A Pepsin B Trypsin C Chymotrypsin D Carboxypeptidase High-Yield Explanation Ans. A. PepsinPepsin is formed when pepsinogen is activated by hydrochloric acid in the stomach. The optimum pH for pepsin action is 1.6 to 3.2.