Where do you think pepsin and trypsin are most active?

Pepsin operates optimally at a pH of two, and trypsin at 3.  Since the stomach is acidic, they would obviously prefer that to the basic lumen of the intestine =]

In the stomach, chief cells release pepsinogen. This zymogen is activated by hydrochloric acid (HCl), which is released from parietal cells in the stomach lining. Pepsin functions best in acidic environments and is often found in an acidic environment, particularly those with a pH of 1.5 to 2..............So,pepsin works only in the stomach not in the small intestine



Trypsin is produced in the pancreas in the form of inactive zymogen, trypsinogen. It is then secreted into the small intestine, where the enzyme enteropeptidase activates it into trypsin. Trypsin have an optimal operating pH of about 8 and optimal operating temperature of about 37°C.............So, Trypsin works only in the small intestine, actually it is not present in the stomach

Hoped it helped..