Changes in glycosylation of human bile-salt-stimulated lipase during lactation

Bile-salt-stimulated lipase (BSSL) is an enzyme in human milk, which is imp ortant for the fat digestion in the newborn infant, BSSL is highly glycosyl ated and includes one site for N-glycosylation and several sites for O-glyc osylation. BSSL has previously been found to express Lewis a, Lewis b, and Lewis x carbohydrate antigens. In this study, glycosylation of BSSL was stu died at different times during lactation. BSSL was purified from milk colle cted individually from four donors at several different times during the fi rst 6 months of lactation. The BSSL glycans were characterized through mono saccharide analysis, high-pH anion-exchange chromatography, matrix-assisted laser desorption-ionization mass spectrometry, and ELISA, Both total carbo hydrate content and relative amount of sialic acid were higher in BSSL from the first lactation month as compared to BSSL from milk collected later in lactation, BSSL from the first lactation month also showed a different com position of sialylated O-linked glycans and the N-linked oligosaccharides c onsisted of lower amounts of fucosylated structures compared to later in la ctation. We also found a gradual increase in the expression of the carbohyd rate epitope Lewis x on BSSL throughout the lactation period. This study sh ows that glycosylation of BSSL is dependent on blood group phenotype of the donor and changes substantially during the lactation period, (C) 2000 Acad emic Press.