Chemistry Reference
In-Depth Information
8
Milk Oligosaccharides
T. Urashima, M. Kitaoka, S. Asakuma, and M. Messer
8.1.
Introduction
Mammalian milk contains up to 10% carbohydrate, of which the disacchar-
ide, lactose (Gal(
1-4)Glc), is usually a prominent component. Milk and
colostrum also contain lesser amounts of other saccharides, referred to as
milk oligosaccharides, nearly all of which have a lactose unit at their reducing
end to which GlcNAc, Gal, Fuc and/or Neu5Ac or Neu5Gc residues can be
attached (Jenness et al., 1964; Newburg and Neubauer, 1995; Boehm and
Stahl, 2003; Urashima et al., 2001; Messer and Urashima, 2002). Pronounced
heterogeneity as well as homology of milk oligosaccharide structures among
different mammalian species has been documented (Urashima et al., 2001;
Messer and Urashima, 2002).
It is well known that free lactose is a significant energy source for human
infants, but the exact biological significance of the milk oligosaccharides
remains to be clarified. The study of milk oligosaccharides was greatly
stimulated by the discovery of a Bifidobacterium growth factor in human
milk and colostrum, but there is still no unequivocal answer to the question of
which oligosaccharides in human milk are responsible for the bifidus factor,
even though it is acknowledged that the oligosaccharide fraction is respon-
sible for promoting the growth of bifidobacteria within the infant colon.
