Polylactosamine chains

L-Fucose may be present in O- and N-glycosylic chains of glycoproteins.85 Polylactosamine chains in O- or N-linked glycans of glycoproteins, or in gly-cosphingolipids, may be modified by attachment of fucose residues, giving rise to blood-group determinants.205... 

Distal a3-sialylation of branched polylactosamines was catalyzed successfully by the activity (ST3Gal IV ) present in human placental microsomes [40, 52] both 3-and 6-linkeci short polylactosamine branches reacted well. More reeently, large, tetravalent sialopolylactosamines have been synthesized in low micromolar amounts (L. Penttila et al., unpublished experiments). Even long polylactosamine chains of blood group i-type are effectively sialylated by placental microsomes [54]. 

Complex-type structures have 2-4 lactosamine (Gal /Jl,4-Gn) units distributed over the two outer Man residues of the core forming bi-, tri-, or tetra-antennary structures. Each of the arms can terminate in sialic acid forming sialyllactosamine. Sulfated lactosamine has been found to substitute sialyl-lactosamine in some cases, such as the glycoprotein hormones EH, FSH and TSH. Other complex-type structures contain polylactosamine in their outer chains, as in erythroglycan. 

Fibromodulin in cartilage and osteoadherin in bone are also modified with A-linked KS chains, as is the PZP3 protein from zona pellucida [14-16]. The cartilage proteoglycan aggrecan was recently shown to contain 2-3 A-linked KS chains in addition to the 20 or more 0-linked KS attachment sites [17]. KSI was also found in dermis of the Pacific mackerel [18]. In addition to these clearly defined examples of KSI, A-linked polylactosamine is a component of numerous cell surface and extracellular glycoproteins, many of these sulfated. It seems likely that future studies will add to the list of KSI-bearing compounds. 

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