Intramolecular zymogen activation

The activation of pepsin from its zymogen pepsinogen occurs by a different mechanism. In this case, the pH of the environment plays a decisive role. In the strongly acidic milieu of the stomach cleavage of a 44 amino acid peptide occurs from the inactive precursor pepsinogen. The activation is intramolecular and depends on the pH of the solution. 

The activation of pepsinogen is thought to occur by two different mechanisms intramolecular, in which the zymogen acts on itself to generate pepsin, and inter-molecular, in which one molecule of pepsin acts on a molecule of pepsinogen to convert it to pepsin. 

Activation is independent of zymogen concentration because the reaction is intramolecular. 

---