What Is the Function of Pepsin in Digestion?

You cut into a juicy pork chop, swallow each bite and don't give the meal a second thought. You may forget the meat once it slips down your throat, but your stomach is hard at work digesting the hunk of protein. An enzyme called pepsin, found in the gastric juices, plays an essential role in breaking down proteins found in meat, eggs, dairy and other foods.

Glands in the lining of your stomach produce and store an inactive form of pepsin called pepsinogen. Hormones gastrin and secretin and nervous impulses from the vagus nerve trigger the release of pepsinogen into the stomach. Pepsinogen reacts with stomach acid, or hydrochloric acid, and becomes the active enzyme -- pepsin. Pepsin partially digests proteins into smaller units called peptides. It works best at a highly acidic pH between 1.5 and 2.5.

Dietary vitamin B-12 is bound to a protein. In order for the vitamin to be absorbed, the protein must be stripped away. Gastric juices and pepsin are part of the cleavage process. Pepsin also cleaves nonheme iron -- which is found in plant foods such as cereals, fruits and vegetables -- from a protein to facilitate absorption.