|Cell culture supernatant||104%||78%-127%|
Pepsinogen I belongs to the peptidase A1 family. The gene endoces a 388 amino acid protein with a 15 amino acid signal peptide and 46 amino acid propeptide. Pepsinogen I is secreted only by the chief cells of the corpus, and its serum level decreases with increasing grade of the corpus atrophy (loss of oxyntic glands). Low serum levels of pepsinogen I are indicative of chronic atrophy, a risk factor for gastric cancer.