Pepsin

Pepsin is a stomach enzyme that breaks proteins into smaller peptides. It is secreted as inactive pepsinogen and activated by the stomach’s acidic environment.

Pepsinogen: Pepsinogen is the inactive precursor secreted by gastric chief cells that becomes pepsin in acidic conditions. Its conversion prevents the enzyme from digesting proteins inside the cells that produce it.
Protein: A protein is a molecule made of one or more chains of amino acids folded into a functional structure. Dietary proteins are pepsin’s substrates.
Gastric digestion: Gastric digestion is the mechanical and chemical breakdown of food within the stomach. Pepsin is the stomach’s principal enzyme for beginning dietary protein breakdown.
Gastroesophageal reflux disease: Gastroesophageal reflux disease is a condition in which stomach contents repeatedly flow into the esophagus and cause troublesome symptoms or injury. Reflux can expose esophageal tissue to pepsin, which may remain damaging beyond the stomach.
Gastric acid: Gastric acid is hydrochloric acid secreted into the stomach, where it creates a strongly acidic environment. Low pH unfolds proteins and enables pepsinogen activation and pepsin activity.
Peptide bond: A peptide bond is the covalent linkage joining the amino group of one amino acid to the carboxyl group of another. Pepsin hydrolyzes peptide bonds to split proteins into shorter peptides.
Peptide mapping: Peptide mapping is an analytical method that identifies proteins by comparing peptides produced through controlled enzymatic cleavage. Pepsin can digest proteins for analysis when acidic conditions suit the experiment.
Peptic ulcer disease: Peptic ulcer disease involves open sores in the stomach or duodenal lining, commonly associated with Helicobacter pylori or NSAID use. Pepsin can contribute to mucosal injury when the stomach’s protective barriers are impaired.
Aspartic protease: An aspartic protease is an enzyme that uses aspartate residues to catalyze protein-bond hydrolysis. Pepsin belongs to this enzyme family and uses catalytic aspartates in its active site.
Amino acid: An amino acid is an organic molecule with amino and carboxyl groups that serves as a protein building block. Amino acids form the chains whose bonds pepsin cleaves.

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