Peptidomic profiling of human milk with LC-MS/MS reveals pH-specific proteolysis of milk proteins

Junai Gan; Randall C Robinson; Jiaqi Wang; Nithya Krishnakumar; Courtney J Manning; Yi Lor; Melissa Breck; Daniela Barile; J Bruce German

doi:10.1016/j.foodchem.2018.09.051

Peptidomic profiling of human milk with LC-MS/MS reveals pH-specific proteolysis of milk proteins

Food Chem. 2019 Feb 15:274:766-774. doi: 10.1016/j.foodchem.2018.09.051. Epub 2018 Sep 10.

Authors

Junai Gan¹, Randall C Robinson², Jiaqi Wang³, Nithya Krishnakumar⁴, Courtney J Manning⁵, Yi Lor⁶, Melissa Breck⁷, Daniela Barile⁸, J Bruce German⁹

Affiliations

¹ Department of Food Science and Technology, University of California Davis, USA. Electronic address: jagan@ucdavis.edu.
² Department of Food Science and Technology, University of California Davis, USA. Electronic address: rcrobinson@ucdavis.edu.
³ Department of Food Science and Technology, University of California Davis, USA. Electronic address: jqqwang@ucdavis.edu.
⁴ Department of Food Science and Technology, University of California Davis, USA. Electronic address: nkumar@ucdavis.edu.
⁵ Department of Chemistry, University of California Davis, USA. Electronic address: cjmanning@ucdavis.edu.
⁶ College of Biological Sciences, University of California Davis, USA. Electronic address: yijlor@ucdavis.edu.
⁷ Department of Food Science and Technology, University of California Davis, USA; Foods for Health Institute, University of California Davis, USA. Electronic address: mabreck@ucdavis.edu.
⁸ Department of Food Science and Technology, University of California Davis, USA; Foods for Health Institute, University of California Davis, USA. Electronic address: dbarile@ucdavis.edu.
⁹ Department of Food Science and Technology, University of California Davis, USA; Foods for Health Institute, University of California Davis, USA. Electronic address: jbgerman@ucdavis.edu.

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.

Keywords: Bioactive peptides; Human milk; Mass spectrometry; Milk peptides; Peptidomics; Protein digestion; Proteolysis.

MeSH terms

Animals
Chromatography, Liquid
Female
Humans
Hydrogen-Ion Concentration
Milk Proteins / chemistry*
Milk Proteins / metabolism*
Milk, Human / metabolism*
Proteolysis*
Proteomics*
Tandem Mass Spectrometry

Substances

Milk Proteins

Abstract

MeSH terms

Substances

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