Comparison of pig and chicken pepsins for protein hydrolysis.

The aim of the present study was to compare the degree of proteolysis with pig (PP) and chicken (CP) pepsins in order to find out whether PP can be used instead of CP to simulate gastric hydrolysis in the chicken. First, the pH activity profile of the two pepsins was compared using three substrates. For haemoglobin, CP showed a slightly higher optimal pH than PP, 2.5-3 and 2, respectively. For two plant protein sources (peas, wheat), the optimal pH was similar for the two enzymes, about pH 1.5. For the three substrates tested, CP exhibited a high level of activity over a broader pH range than PP. Second, the susceptibility of the two plant proteins to hydrolysis by each of the two pepsins was studied at pH levels near the chicken gastric pH (1.5-3.5). For PP, pea proteins were hydrolysed more than wheat ones, while, for CP, the hydrolysis was dependent on pH. Therefore, the classification of the two studied protein sources was dependent on the enzyme species and pH. The results of this study show that the choice of in vitro hydrolysis conditions to assess the digestibility of proteins must be made with great care.