How is pepsinogen activated to its active form, pepsin?

Pepsinogen is an inactive precursor, or zymogen, of the enzyme pepsin, which plays a crucial role in the digestion of proteins in the stomach. The activation of pepsinogen to its active form, pepsin, occurs through a process called acidic proteolysis, specifically autocleavage.

When pepsinogen is secreted by the gastric chief cells, it is initially inactive and requires the acidic environment of the stomach (primarily due to hydrochloric acid secreted by the parietal cells) to undergo a conformational change. The low pH causes specific peptide bonds within pepsinogen to break, leading to the removal of a small peptide fragment. This cleavage results in the activation of pepsinogen into pepsin, which can then begin hydrolyzing protein substrates in their native state.

This cleavage is efficient and precise, as it ensures that pepsinogen does not become active until it reaches the acidic environment designed for protein digestion in the stomach. The ability of pepsin to become active in such an acidic environment is a key aspect of its function.

The other choices describe processes that are not related to the activation of pepsinogen. For instance,