Activation of Partially Purified Pepsinogen

Pepsinogen can be extracted from the mucosa of the fundus part of pig stomachs by m/10 NaHCO₃-solution. Such extracts contain 80-90% of the total peptic activity of the mucosa (as determined after complete autolysis of the mucosa at pH 2) in the form of pepsinogen which is stable at alkaline reaction. The extract is treated with Filtercel† to remove most of the mucilaginous material, which otherwise renders the extract very difficult to handle. The pepsinogen may then be gradually purified by fractional precipitation with ammonium sulphate at pH 7. (Table I.)

The total peptic activity (pepsinogen + preformed pepsin) of the various samples was determined by the hemoglobin method 1 at pH 1.8, all pepsinogen being activated at this pH. 2 , 3 Pepsinogen alone was estimated as the difference between the total activity just mentioned and the activity of samples which previously had been titrated to pH 9 in order to destroy preformed pepsin. The activity is expressed in pepsin units [P.U.]^Hb, 4 the “specific activity” (Q) being the ratio between the total number of pepsin units (pepsinogen + pepsin) and the amount of nitrogen precipitated by 4% CCl₂COOH at 80°: . The course of one preparation is given schematically in Table I.