Enzymatic characterization of CMP-NeuAc:Gal beta 1-4GlcNAc-R alpha(2-3)-sialyltransferase from human placenta.
In this report we present the enzymatic characterization of CMP-NeuAc:Gal beta 1-4GlcNAc-R alpha(2-3)-sialyltransferase from human placenta using placenta membranes as an enzyme preparation. This sialyltransferase is highly sensitive to detergents and prefers type 2 chain (Gal beta 1-4GlcNAc) over type 1 chain (Gal beta 1-3GlcNAc) acceptors. Oligosaccharides and glycopeptides were better acceptor substrates than glycoproteins. Of the branched oligosaccharides, those with a bisected N-acetylglucosamine (GlcNAc) structure appeared to be poorer substrates, while triantennary structures containing a Gal beta 1-4GlcNAc beta 1-4Man alpha 1-3Man branch were preferred. Product characterization, using 400 MHz 1H-NMR spectroscopy, confirmed that sialic acid was introduced into the Gal beta 1-4GlcNAc-R units of the acceptor substrates in an alpha (2-3) linkage, and revealed that this sialyltransferase does not prefer either of the two branches of a complex type di-antennary glycopeptide acceptor for sialic acid attachment. These properties distinguish this enzyme from all other sialyltransferases characterized to date.
Department of Medical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.
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Nemansky
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van den Eijnden
D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D005260:Female; D006020:Glycopeptides / Q000302:isolation & purification; D006801:Humans; D008099:Liver / Q000201:enzymology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008969:Molecular Sequence Data; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011522:Protons; D051381:Rats; D012799:Sialyltransferases / Q000737:chemistry*; D013379:Substrate Specificity
D006020:Glycopeptides; D011522:Protons; D012799:Sialyltransferases; C029156:N-acetyllactosaminide alpha-2,3-sialyltransferase