Introduction:
The aim of this study was to develop a method to assay the activity of pepsin in gastric juice based on the method described in the references, which was not entirely effective in laboratory tests. The study aims to improve the aforementioned method based on the digestion of bovine hemoglobin by pepsin and to introduce effective changes so that the results may be useful for diagnostic purposes.

Materials and methods:
To achieve this, tests were carried out using the hemoglobin of different species of animals and human hemoglobin, changing the incubation periods, concentrations and volumes of reagents.

Results:
Tests based on the use of purified (crystalline) pepsin revealed that the most effective in the assay of enzyme activity is human hemoglobin. The originally proposed incubation periods were extended, and in order to inhibit the reaction, trichloroacetic acid was used in a higher concentration than suggested, while reducing by half the volume of reactants. In the tests carried out using a purified enzyme, a correlation between the known concentration of the enzyme and the absorbance of supernatant containing the reaction products of enzymatic digestion of hemoglobin was proved.

Conclusions:
Introducting changes leads to more effective diagnostic use.