Gastric proteolysis in disease. 4. Proteinase activity of extracts of human gastric adenocarcinomata.

Resting gastric juice and extracts of uninvaded gastric mucosa from the stomachs of patients with gastric adenocarcinomata digest plasma protein with either two or three maxima below pH 5. Egg albumen is digested with one or two maxima below pH 5, for the maximum found near pH 3.5 with plasma protein is absent. These properties do not differ significantly from those described in normal subjects. Extracts of gastric adenocarcinomatous tissue from the same patients differ in that plasma protein is digested with only one maximum, at pH 3.2 to 3.4, and egg albumen is not digested at all. The proteinase activity of the carcinomatous tissue probably arises from adenocarcinomatous cells and not from invaded muscle cells or reactive fibrous tissue. These results could be explained either (a) if gastric adenocarcinomatous cells synthesized a quite different proteinase from those of normal gastric mucosa, or (b) if they synthesized a proteinase, which resembled those of normal mucosa in possessing the active centre responsible for maximal activity near pH 3.5 but in which the centre or centres responsible for maximal activity below pH 3, were missing.