title: Purification and properties of GM2 synthase, UDP-N-acetylgalactosamine: GM3 beta-N-acetylgalactosaminyltransferase from rat liver.
abstract: A UDP-N-acetylgalactosamine:ganglioside GM3 beta-N-acetylgalactosaminyltransferase which catalyzes the conversion of ganglioside GM3 to GM2 has been purified over 6300-fold from a Triton X-100 extract of rat liver particulate fractions by hydrophobic chromatography and affinity chromatography on GM3-acid-Sepharose. The purified enzyme has two identical subunits of 64,000 daltons. The enzyme has a pH optimum of pH 6.7-6.9 and requires divalent cations such as Mn2+ and Ni2+. In studies on substrate specificity GM3 containing N-acetylneuraminic acid (GM3(NeuAc] and GM3 containing N-glycolylneuraminic acid were both good acceptors for the purified enzyme. The plots of the activity of transferase as a function of GM3(NeuAc) showed sigmoidal relationships. The oligosaccharide of GM3, sialyllactose, was also a good acceptor, which indicates that the preferred acceptor substrate has the possible structure NeuAc alpha 2- or NeuGc alpha 2-3 Gal beta 1-4Glc-OR.
mesh_terms: D000818:Animals; D002413:Cations, Divalent / Q000378:metabolism; D002845:Chromatography; D005678:G(M2) Ganglioside / Q000096:biosynthesis*; D005700:Galactosyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D005732:Gangliosides / Q000096:biosynthesis*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D017350:N-Acetylgalactosaminyltransferases; D051381:Rats; D000097763:Polypeptide N-acetylgalactosaminyltransferase
chemical_list: D002413:Cations, Divalent; D005678:G(M2) Ganglioside; D005700:Galactosyltransferases; D005732:Gangliosides; D017350:N-Acetylgalactosaminyltransferases; D000097763:Polypeptide N-acetylgalactosaminyltransferase; C023220:(N-acetylneuraminyl)-galactosylglucosylceramide N-acetylgalactosaminyltransferase