Nonenzymatic lactosylation of bovine beta-lactoglobulin under mild heat treatment leads to structural heterogeneity of the glycoforms.
Lactose reacts nonenzymatically with beta-lactoglobulin (beta-LG), the major whey protein, under mild heat treatment and the formation of the complex may be monitored by mass spectrometry. Using Reverse Phase HPLC coupled with Electrospray Ionization MS (ESI-MS) we have measured the global extent of glycosylation and examined the distribution of lactose among the beta-LG glycoforms. Identification of lactosylated sites by trypsinolysis and Tandem MS indicate that, although the glycosylation reaction was non-specific and potentially involved all the reactive sites (alpha- and epsilon-amino groups), beta-LG appeared to have at least two populations of lysine with the distinct ability to react with lactose. These results underline the structural heterogeneity of beta-LG glycoforms, with respect to the number of lactose linked per molecule and to the binding sites involved, which could affect the biological function of beta-LG.
Morgan
F
F
Laboratoire de Recherches de Technologie Laitière, INRA, Rennes, France.
Léonil
J
J
Mollé
D
D
Bouhallab
S
S
D000588:Amines / Q000737:chemistry; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D006031:Glycosylation; D006358:Hot Temperature; D007782:Lactoglobulins / Q000737:chemistry*; D007785:Lactose / Q000737:chemistry; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010449:Peptide Mapping
D000588:Amines; D007782:Lactoglobulins; D007785:Lactose