Biosynthesis of mammary glycoproteins. Structural characterization of lipid-linked glucosyloligosaccharides.
The lipid-linked glucosyloligosaccharide intermediates for the biosynthesis of asparagine-linked glycoproteins in the lactating bovine mammary tissue were isolated from incubations of microsomes of this tissue with labeled sugar-nucleotides. These were shown to have the general structure (Glc)1 -3(Man)9(GlcNAc)2. A structural characterization indicated that glucose residues in these oligosaccharides are linked as Glc alpha 1 leads to 3, Glc alpha 1 leads to 3Glc alpha 1 leads to 3, and Glc1 leads to 2Glc alpha 1 leads to 3Glc alpha 1 leads to 3, to the tetramannosyl branch of (Man)9(GlcNAc)2 portion previously characterized as Man alpha 1 leads to 2Man alpha 1 leads to 2Man alpha 1 leads to 3(Man alpha 1 leads to 2Man alpha 1 leads to 6[Man alpha 1 leads to 2Man alpha 1 leads to 3]-Man alpha 1 leads to 6)Man beta 1 leads to 4(3)GlcNAc beta 1 leads to 4(3)GlcNAc [Vijay, I. K., Perdew, G. H., and Lewis, D. E. (1980) J. Biol. Chem. 255, 11210-11220]. The lipid-linked (Man)9(GlcNAc)2 appears to be the initial acceptor of the first glucosyl residue. Even though incubations of the bovine mammary tissue in vitro synthesize multiple isomers of a number of mannosyloligosaccharides, the glucosyloligosaccharides are all monoisomeric.
D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D005260:Female; D005947:Glucose / Q000032:analysis; D006023:Glycoproteins / Q000096:biosynthesis*; D066298:In Vitro Techniques; D007774:Lactation; D008055:Lipids / Q000032:analysis*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D009844:Oligosaccharides / Q000032:analysis*; D011247:Pregnancy
D006023:Glycoproteins; D008055:Lipids; D009844:Oligosaccharides; D005947:Glucose