Pepsin is an enzyme that plays a crucial role in the digestion of proteins in the stomach. It is produced in an inactive form called pepsinogen by the stomach lining and is activated by the acidic environment created by hydrochloric acid. Once activated, pepsin breaks down proteins into smaller peptides, making them easier for the body to absorb. This enzyme works best in the acidic conditions of the stomach, with an optimal pH around 1.5 to 2. Pepsin is essential for proper digestion, as it helps to initiate the breakdown of dietary proteins, which are vital for various bodily functions, including tissue repair and enzyme production.