Characterization of the C-terminal region of molecular forms of human milk bile salt-stimulated lipase.
Bile salt-stimulated lipase (BSSL) in human milk exists in multiple molecular forms and it has been shown that approximately one-third of lactating mothers secrete two forms.


OBJECTIVE
to determine the structural features of BSSL that may give rise to this heterogeneity.


METHODS
Oligosaccharides present in the proline-rich region in the C-terminus of BSSL were investigated using deglycosylating enzymes and lectin affinity probing to determine the origin of the multiple molecular forms.


RESULTS
It was found that the variability in the molecular mass of BSSL is due predominantly to glycosylation. The molecular forms contain similar sugar chains; all forms possess the core disaccharide Galbeta1-3GalNAc and beta-D-galactose, fucose linked at alpha1-6 and sialic acid linkage alpha2-3 to galactose.


CONCLUSIONS
The molecular mass difference in the BSSL molecular forms cannot be attributed to the type of carbohydrate moiety in the sugar chains of the N- and O-linked sites suggesting that the differences arise from the extent or quantity of glycosylation. The oligosaccharides in the C-terminal region contain Lewis x and b and, less prominently, Lewis a antigenic structures. Owing to the presence of these blood-group-related antigenic determinants, the C-terminal region of BSSL may have an adhesive function in cell-cell interactions.
The Queen's University of Belfast, Department of Child Health, Institute of Clinical Science, Belfast, N. Ireland. am.mckillop@ulster.ac.uk
A M
AM
McKillop
M M T
MM
O'Hare
J S
JS
Craig
H L
HL
Halliday
D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006031:Glycosylation; D006801:Humans; D037102:Lectins / Q000378:metabolism*; D008895:Milk, Human / Q000737:chemistry*; D002787:Sterol Esterase / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
D037102:Lectins; C054784:bile salt-stimulated lipase; D002787:Sterol Esterase