GLYCOSYLATION OF BILE-SALT-STIMULATED LIPASE FROM HUMAN-MILK - COMPARISON OF NATIVE AND RECOMBINANT FORMS

Bile-salt-stimulated lipase (BSSL) is an enzyme present in human milk. BSSL is important for fat digestion in infants, It contains one site for N-glycosylation and a serine/threonine-rich domain which is highly O-glycosylated. Both N- and O-linked sugar chains were studied on nat ive BSSL from three donors and compared to the glycosylation of recomb inant BSSL produced in Chinese hamster ovary or mouse fibroblast (C-12 7) cell lines. The carbohydrate composition of oligosaccharides was ma pped using sugar and methylation analyses, enzyme-linked immunosorbant assay, and different separation techniques. Native BSSL was found to be highly glycosylated (19-26%). It contained a high amount of fucosyl ated oligosaccharides and expressed both Lewis a and Lewis b blood gro up antigens. None of the recombinant BSSL forms contained fucose. N-li nked structures an native BSSL were identified as mainly mono-and disi alylated biantennary complex type structures with or without fucose su bstitution. High-pH anion-exchange chromatography analysis indicated t hat the recombinant forms of BSSL contained similar types of N-glycan structures differing mainly in their content of sialic acid and by the absence of fucose residues. Native BSSL contained predominantly large O-linked oligosaccharides. This was in contrast to the recombinant fo rms of BSSL which contained mainly short type O-glycans with a high co ntent of sialic acid. Interestingly, the estimated number of O-glycans attached to native BSSL was lower than that for the recombinant forms . (C) 1997 Academic Press.