ISSN:
1573-4986
Keywords:
Glycosyltransferase
;
N-acetyllactosamine
;
biosynthesis
;
radiolabel
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Poly-N-acetyllactosamines provide backbone structures for functional modifications such as sialyl Lewis X. To understand how the biosynthesis of poly-N-acetyllactosamines is regulated, two branched oligosaccharides of the structure Galβ1,4GlcNAcβ1, 6(Galβ1,4GlcNAcβ1,2)-Manα1,6Manβ-octyl 1 and 2 were synthesized in which one of the terminal galactose units was selectively radiolabeled. Hexasaccharides 1 and 2 were assembled from the chemically synthesized pentasaccharide precursors GlcNAcβ1,6(Galβ1,4GlcNAcβ1,2)-Manα1,6Manβ-octyl3 and Galβ1,4GlcNAcβ1,6(GlcNAcβ1, 2) - Manα1,6 Manβ-octyl 4 respectively, through treatment with UDP-1-[3H]-Gal and β1,4 galactosyltransferase. Compounds 1 and 2 were subsequently incubated with UDP-GlcNAc and the UDP-GlcNAc: Galβ1-4Glc(NAc)β1,3-N-acetylglucosaminyltransferase (i-GlcNAc transferase) resulting in a partial conversion to a mixture of heptasaccharides which were purified by HPLC. The branch selectivity of the addition of N-acetylglucosamine to compounds 1 and 2 was then characterized by endo-β-galactosidase digestion of the heptasaccharides, followed by isolation of the resultant pentasaccharides on C18 reverse-phase silica cartridges. Comparison of the amount of radiolabel to a control reaction lacking endo-β-galactosidase indicated the favored site of GlcNAc addition to be the lower β1,2-branch over the β1,6-branch by a 3:1 ratio.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1007167529125
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