The stability of human pepsins in stored gastric juice

The effect of storage at -20 degrees C and +2 degrees C on the pepsins of human gastric juice was assessed by quantitative assay and agar gel electrophoresis. Quantitative assays showed no significant loss of peptic activity at either temperature over periods of storage up to 3 weeks, and no correlation between change in peptic activity and the acidity of the gastric juice, although raising the pH of the gastric juice above pH 2 with buffers gave improved stability over gastric juice mixed with buffer of lower pH. At low pH, the addition of bovine serum albumin gave improved stability. Agar gel electrophoresis showed that the pepsins were all stable at -20 degrees C for several days or several weeks, but alterations occurred in the pepsin molecules after several months.