Plasma group I pepsinogen (PG I) concentration is now a readily available non-invasive marker of gastric secretory function, with several potentially useful applications. Ninety-eight percent of control subjects had a plasma PG I below 115 ng/ml while values above this level were seen in 43% of duodenal ulcer patients. Plasma PG I levels below the observed normal lower limit of 30 ng/ml were se...

The spontaneous and pepsin-catalyzed activation of pepsinogen has been observed and analyzed kinetically. At appropriate protein concentrations (1 mg per ml or less), a kinetically first order reaction was observed in the pH range 1 to 3, implying an intramolecular activation mechanism. Substantiation of the first order reaction came from a linear plot of log pepsinogen concentration versus tim...

A study of the kinetics of the transformation of swine pepsinogen into pepsin under a variety of conditions has been made. The results show that the transformation as a whole is essentially autocatalytic in nature under all conditions. Evidence is presented to show the existence of a compound intermediate between pepsinogen and pepsin. This compound was found to be a reversibly dissociable comp...