Pepsin is “an inactive form of pepsinogen that is produced in the stomach”. It activates only during the digestion process and breaks down the proteins in the food into components like peptones, proteoses and polypeptides. This protein digesting enzyme is stimulated by hydrochloric acid (HCl) in the digestive tract. It was the very first enzyme to be acknowledged. This enzyme is naturally produced in the stomach, but some supplements can also stimulate it.
Pepsin is composed of six helical sections, and every section consists of less than ten amino acids and organic compounds. It contains 44 amino acids on its N-terminus, released during the transformation process.
Image Courtesy: biyolojiegitim.yyu.edu.tr
It is the pro-form of pepsin that is produced in the stomach by gastric chief cells – also known as gastric zymogenic cells and peptic cells. The major portion of pepsinogen is secreted into the gastric lumen, while a small proportion can be found in the blood. Pepsinogen I and pepsinogen II are the major forms of this digestive enzyme, depending on the site of production/secretion.