Conclusions
This study documents that selective proteolysis activated by pH shift is a mechanism for dynamic interactions between human milk and the infant. Controlled proteolysis can guide the use of human milk products based on individual circumstance.
Results
Endogenous proteolysis is characterized by incubating freshly expressed human milk at physiologically relevant pH ranging from 2 to 7 without the addition of exogenous enzymes. Results show that the effects of pH on endogenous proteolysis in human milk are protein-specific. Further, specific interactions between cathepsin D and α-lactalbumin are confirmed. The endogenous enzyme cathepsin D in human milk cleaves α-lactalbumin as the milk pH shifts from 7 to 3. Conclusions: This study documents that selective proteolysis activated by pH shift is a mechanism for dynamic interactions between human milk and the infant. Controlled proteolysis can guide the use of human milk products based on individual circumstance.