Sialylation in vitro of purified human liver beta-D-N-acetylhexosaminidase.
In order to study structure-function relationships of lysosomal enzymes, human liver beta-N-acetylhexosaminidase (2-acetamido-2-deoxy-beta-D-hexoside acetamidodeoxyhexohydrolase, EC 3.2.1.52) has been purified by an extraction/affinity chromatography/ion-exchange procedure. The isoenzymes A and B, native as well as neuraminidase-treated, were incubated with a partially purified preparation of bovine colostrum sialyltransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1). Native beta-N-acetylhexosaminidases were found to be poor acceptors for the sialyltransferase used. However, incorporation of sialic acid into neuraminidase-treated beta-N-acetylhexosaminidase A and B amounted to a 58 to 72% saturation of the theoretical acceptor sites, respectively. The acceptor specificity of the sialyltransferase suggests that Gal beta(1 leads to 4)-GlcNAc units may be present on at least part of the beta-N-acetylhexosaminidase A and B molecules. However, oligomannosidic-type chains may also occur on the lysosomal enzyme, as shown by sugar composition of the enzyme. The presence and/or amount of sialic acid residues does not appear to affect the kinetic properties of beta-N-acetylhexosaminidase A and B towards 4-methylumbelliferyl glycoside substrate.
D003126:Colostrum / Q000201:enzymology; D006596:Hexosaminidases / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007525:Isoelectric Focusing; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D009439:Neuraminidase; D012794:Sialic Acids / Q000378:metabolism*; D012799:Sialyltransferases / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*; D001619:beta-N-Acetylhexosaminidases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
D007527:Isoenzymes; D012794:Sialic Acids; D014166:Transferases; D012799:Sialyltransferases; D006596:Hexosaminidases; D009439:Neuraminidase; D001619:beta-N-Acetylhexosaminidases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase