Peptidomic profiling of human milk with LC–MS/MS reveals pH-specific proteolysis of milk proteins. (15th February 2019) - Gan, Junai
Highlights: Human milk contains a dynamic proteolytic system. Selective proteolysis of milk proteins into specific peptides was pH-dependent. Seventy-four human milk peptides were consistently found despite pH alterations. Eight peptides were released only at pH 4 or 5 (typical infant gastric pH). Total concentration of peptides was not significantly changed by pH alterations. Abstract: Human milk is a dynamic protein-protease system that delivers bioactive peptides to infants. The pH of milk changes from the mother's mammary gland to the infant's digestive tract. Although the release of human milk peptides has been studied during in vivo or in vitro digestion, these models did not explicitly vary nor observe the effect of pH. The objective of this research was to determine the effect of pH on the proteolysis of human milk. Using high-resolution accurate-mass Orbitrap mass spectrometry, profiles of endogenous human milk peptides before and after incubation at various pH levels have been mapped. Over 5000 peptides were identified. Comparative analyses classified 74 peptides that were consistently found independent of pH alterations, and 8 peptides that were released only at pH 4 or 5 (typical infant gastric pH). Results documented that the proteolysis of milk proteins, particularly β-casein, polymeric immunoglobulin receptor, and α-lactalbumin, is pH-dependent.