Glycosyltransferases of the human cervical epithelium. II. Characterization of a CMP-N-acetylneuraminate: galactosyl-glycoprotein sialyltransferase.
GMP-N-Acetylneuraminate: galactosyl-glycoprotein sialytransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity was identified in the human cervical epithelium. The enzyme has a pH optimum of 6.0, a temperature optimum of 28 degrees C, and demonstrates a partial requirement for Triton X-100. Michaelis constants for asialofetuin and CMP-N-acetyl[14C]neuraminic acid are 0.64 . 10(-5) M (expressed as the concentration of terminal galactose residues) and 2.05 . 10(-5) M, respectively. Sialytransferase demonstrated minimal affinity for the low molecular weight acceptors tested, and may have a requirement for a glycoprotein acceptor having  a terminal N-acetyllactosamine (Gal beta (1 leads to 4)GlcNAc) type structure. Cytidine nucleotides are potent inhibitors of the sialyltransferase reaction; CMP acts as a competitive inhibitor.
D001212:Asialoglycoproteins; D002584:Cervix Uteri / Q000201:enzymology*; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid / Q000378:metabolism; D003597:Cytosine Nucleotides / Q000494:pharmacology; D004848:Epithelium / Q000201:enzymology; D005260:Female; D060748:Fetuins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000494:pharmacology; D012799:Sialyltransferases / Q000032:analysis* / Q000378:metabolism; D013379:Substrate Specificity; D013696:Temperature; D014166:Transferases / Q000032:analysis*; D000509:alpha-Fetoproteins / Q000378:metabolism; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D001212:Asialoglycoproteins; D003597:Cytosine Nucleotides; D060748:Fetuins; D000509:alpha-Fetoproteins; C017029:asialofetuin; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid; D011092:Polyethylene Glycols; D017830:Octoxynol; D014166:Transferases; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase