title: Protein-Linked Glycan Degradation in Infants Fed Human Milk.
abstract: Many human milk proteins are glycosylated. Glycosylation is important in protecting bioactive proteins and peptide fragments from digestion. Protein-linked glycans have a variety of functions; however, there is a paucity of information on protein-linked glycan degradation in either the infant or the adult digestive system. Human digestive enzymes can break down dietary disaccharides and starches, but most of the digestive enzymes required for complex protein-linked glycan degradation are absent from both human digestive secretions and the external brush border membrane of the intestinal lining. Indeed, complex carbohydrates remain intact throughout their transit through the stomach and small intestine, and are undegraded byin vitroincubation with either adult pancreatic secretions or intact intestinal brush border membranes. Human gastrointestinal bacteria, however, produce a wide variety of glycosidases with regio- and anomeric specificities matching those of protein-linked glycan structures. These bacteria degrade a wide array of complex carbohydrates including various protein-linked glycans. That bacteria possess glycan degradation capabilities, whereas the human digestive system, perse, does not, suggests that most dietary protein-linked glycan breakdown will be of bacterial origin. In addition to providing a food source for specific bacteria in the colon, protein-linked glycans from human milk may act as decoys for pathogenic bacteria to prevent invasion and infection of the host. The composition of the intestinal microbiome may be particularly important in the most vulnerable humans-the elderly, the immunocompromised, and infants (particularly premature infants).
authors.affiliation: Department of Food Science and Technology, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA ; Foods for Health Institute, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: David C
authors.initials: DC
authors.lastname: Dallas
authors.affiliation: Department of Viticulture and Enology, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: David
authors.initials: D
authors.lastname: Sela
authors.affiliation: Foods for Health Institute, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA ; Department of Pediatrics, University of California Davis, 2315 Stockton Blvd, Sacramento, CA, 95817, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Underwood
authors.affiliation: Department of Food Science and Technology, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA ; Foods for Health Institute, University of California at Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: J Bruce
authors.initials: JB
authors.lastname: German
authors.affiliation: Department of Chemistry, University of California Davis, One Shields Avenue, Davis, CA, 95616, USA.
authors.forename: Carlito
authors.initials: C
authors.lastname: Lebrilla
keywords: Bacteria; Digestion; Glycan; Glycoprotein; Glycosidase; Human milk; Infant; Microbiota; Prebiotic; Protein-linked glycan