Acidic environment of stomach helps conversion of pepsinogen into pepsin which is most important to digest the protein into smaller component like complex protein into simple peptides and amino acids inside stomach which is later absorbs by gastro intestinal tract. (en.wikipedia.org)
Achlorhydria may also be documented by measurements of extremely low levels of pepsinogen A (PgA)(< 17 µg / L) in blood serum. (en.wikipedia.org)
She determined the structural difference between pepsin and its precursor pepsinogen, analyzed the proteins» shapes, and determined how temperature and chemical conditions influence their structures. (sciencemag.org)