Question

Enzymes are both pH and temperature specific. Seen here are the reaction rates of three common digestive enzymes. Based on the data, which enzyme(s) require(s) the addition of HCl for optimum activity
A) pepsin
Eliminate

B) trypsin


C) amylase


D) none of the three

Answer 1

It is (A)pepsin 
Eliminate 

Answer 2

The right answer is A) pepsin

* Pepsin is an endoprotease that hydrolyzes peptide bonds in which an aromatic amino acid (Tyr, Trp, Phe) engages its amine function.

* Pepsin is an enzyme of gastric juice. It is synthesized as pepsinogen (inactive proenzyme) and then stored in the enzymatic vesicles of the main cells, from which it is excreted at the time of digestion. The activation of pepsinogen pepsin is the result of acid hydrolysis in the acidic environment of the stomach. The pepsinogen (43,000 MW) then loses several fragments, one of 29 amino acids (pepsin inhibitor) whose hydrolysis causes the activation of pepsin. The optimum pH of action of pepsin is between 1.8 and 4.4 and is inactivated by the alkaline bicarbonates of the pancreatic juice.