title: Sialylation of glycoprotein oligosaccharides with N-acetyl-, N-glycolyl-, and N-O-diacetylneuraminic acids.
abstract: Four common sialic acids (Sia), NeuAc, N-glycolyl-neuraminic acid (NeuGc), 4-O-acetyl-N-acetylneuraminic acid (4-O-Ac-NeuAc), and 9-O-Ac-NeuAc were examined for activation to their corresponding CMP-sialic acid conjugates and subsequently for their transfer to glycoprotein oligosaccharides by purified mammalian sialyltransferases. CMP-sialic acid synthetases from calf brain and from bovine and equine submaxillary glands were found to convert NeuAc, NeuGc, and 9-O-Ac-NeuAc to their corresponding CMP-sailic acids. In contrast, no conversion of 4-O-Ac-NeuAc to CMP-4-O-Ac-NeuAc was observed for any of the three synthetases examined. A new procedure for the preparation of CMP-9-O-Ac-NeuAc, CMP-NeuGc, and CMP-NeuAc in high yield and purity was developed, using the calf brain CMP-sialic acid synthetase. Each of these derivatives was tested as donor substrates for six mammalian sialyltransferases purified from porcine, rat, and bovine tissues, including a bovine GalNAc alpha 2,6 sialyltransferase whose purification is described in this report. The sialyltransferases examined represent those which form the Sia alpha 2,6Gal beta 1,4-GlcNAc-, Sia alpha 2,3Gal beta 1,3(4)GlcNAc-, Sia alpha 2,3Gal beta 1,3-GalNAc- and Sia alpha 2,6GalNAc- sequences found on N-linked and O-linked oligosaccharides of glycoproteins. CMP-NeuAc and CMP-NeuGc were equally good donor substrates for all six sialyltransferases. However, transfer of 9-O-Ac-NeuAc from CMP-9-O-Ac-NeuAc varied from only 10% to nearly 70% that of the transfer of NeuAc from CMP-NeuAc. Results are viewed to define the relative roles of direct transfer of these sialic acids and modification of glycosidically bound NeuAc in glycoproteins.
mesh_terms: D000107:Acetylation; D000818:Animals; D002417:Cattle; D003568:Cytidine Monophosphate / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008345:Manganese / Q000494:pharmacology; D019158:N-Acetylneuraminic Acid; D000216:N-Acylneuraminate Cytidylyltransferase / Q000302:isolation & purification / Q000494:pharmacology; D009438:Neuraminic Acids / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism*; D012794:Sialic Acids / Q000096:biosynthesis*; D012799:Sialyltransferases / Q000302:isolation & purification / Q000494:pharmacology; D013363:Submandibular Gland / Q000201:enzymology; D013552:Swine
chemical_list: D006023:Glycoproteins; D009438:Neuraminic Acids; D009844:Oligosaccharides; D012794:Sialic Acids; C032592:N-glycolylneuraminic acid; D008345:Manganese; C025676:9-O-acetyl-N-acetylneuraminic acid; D012799:Sialyltransferases; D000216:N-Acylneuraminate Cytidylyltransferase; D003568:Cytidine Monophosphate; D019158:N-Acetylneuraminic Acid; D008274:Magnesium