Structural and functional characteristics of bovine milk protein glycosylation

Abstract

Most secreted and cell membrane proteins in mammals are glycosylated. Many of these glycoproteins are also prevalent in milk and play key roles in the biomodulatory properties of milk and ultimately in determining milk's nutritional quality. Although a significant amount of information exists on the types and roles of free oligosaccharides in milk, very little is known about the glycans associated with milk glycoproteins, in particular, the biological properties that are linked to their presence. The main glycoproteins found in bovine milk are lactoferrin, the immunoglobulins, glycomacropeptide, a glycopeptide derived from κ-casein, and the glycoproteins of the milk fat globule membrane. Here, we review the glycoproteins present in bovine milk, the information currently available on their glycosylation and the biological significance of their oligosaccharide chains.

Separation of monosaccharides hydrolyzed from glycoproteins without the need for derivatization

“…The precursor and product ions from NANA and NGNA are non-isobaric, consequently, these monosaccharides are distinguishable in the mass spectrometer. Sialic acids and galactose have been reported in the literature [21][22][23][24] as major monosaccharide components in O-linked glycoforms of casein, and were observed in this work. A peak corresponding to mannose was observed but was determined to be due to contamination.…”

Milk Glycans and Their Interaction with the Infant-Gut Microbiota

“…Bovine milk contains some of the same glycoconjugates as human milk, such as lactoferrin, immunoglobulins, glycoproteins from the MFGM, and gangliosides (O’Riordan et al 2014). Additionally, dairy streams contain significant amounts of glycomacropeptide (GMP), which is a heavily sialylated glycopeptide derived from hydrolysis of κ-casein during cheesemaking (Neelima et al 2013).…”

How Milk and Its Proteins Affect Growth, Bone Health, and Weight

“…Moreover, milk proteins, lipids and carbohydrates, including lactose, free oligosaccharides [6], and bound glycans or glycoconjugates [7] may affect the gut microbiome, leading to a more efficient utilization of food. The influence of diet on the gut microbiome has been receiving increasing attention, with studies showing the specific effect on bacterial growth of oligosaccharides released from milk glycoproteins [12] or in the whey and casein fraction (our unpublished data).…”

“…The carbohydrate fraction of bovine milk is divided into lactose (48 g/L), free oligosaccharides (0.05 g/L) [6], and bound glycans or glycoconjugates present in milk glycolipids and glycoproteins [7]. Casein and whey differ in their glycoprotein content.…”