Pepsin is a powerful digestive enzyme that works in your stomach to break down proteins from food into smaller pieces your body can use. When you eat a piece of chicken or a handful of nuts, pepsin goes to work splitting apart the long, complex protein molecules into shorter chains called peptides.

Your stomach produces pepsin in an inactive form called pepsinogen. When food arrives and your stomach releases acid, pepsinogen transforms into active pepsin and begins its work. Pepsin is specially designed to function in the extremely acidic environment of your stomach, where most other enzymes would be destroyed.

Scientists discovered pepsin in the 1830s, making it one of the first enzymes ever identified. This discovery helped researchers understand that digestion isn't just about churning food mechanically but involves specific chemicals that break down different nutrients. Without pepsin and other digestive enzymes, your body couldn't extract the amino acids it needs from the proteins you eat, no matter how thoroughly you chewed.