Bovine colostrum CMP-NeuAc:Gal beta(1-->4)GlcNAc-R alpha(2-->6)-sialyltransferase is involved in the synthesis of the terminal NeuAc alpha(2-->6)GalNAc beta(1-->4)GlcNAc sequence occurring on N-linked glycans of bovine milk glycoproteins.
Bovine colostrum CMP-NeuAc:Gal beta(-->4)GlcNAc-R alpha(2-->6)-sialyltransferase (alpha 6-sialyltransferase) appears to be capable of catalysing alpha 6-sialylation of the disaccharide GalNAc beta(1-->4)GlcNAc to yield the trisaccharide NeuAc alpha(2-->6)GalNAc beta(1-->4)GlcNAc. This provides an enzymic basis for the occurrence of this sialylated structure on the N-linked glycans of a number of bovine milk glycoproteins. Competition experiments using Gal beta(1-->4)GlcNAc and GalNAc beta(-->4)GlcNAc as acceptors indicate that both substrates are recognized by a single active site on the alpha 6-sialyltransferase. Extrapolation of these results suggests that the NeuAc alpha(2-->6)GalNAc beta(1-->4)GlcNAc structural element occurring on the N-linked glycans of several human glycoproteins are similarly synthesized by the action of a Gal beta(1-->4)GlcNAc-R alpha(2-->6)-sialyltransferase.
Nemansky
M
M
Department of Medical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.
Van den Eijnden
D H
DH
D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D003126:Colostrum / Q000201:enzymology*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008894:Milk Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism; D012799:Sialyltransferases / Q000378:metabolism*; D013379:Substrate Specificity
D006023:Glycoproteins; D008894:Milk Proteins; D011134:Polysaccharides; D012799:Sialyltransferases