title: Purification and characterization of UDP-N-acetylgalactosamine GM3/GD3 N-acetylgalactosaminyltransferase from mouse liver.
abstract: A UDP-N-acetylgalactosamine: Sia alpha 2-3Gal beta 1-4Glc beta 1-/Sia alpha 2-8Sia alpha 2-3Gal beta 1-4Glc beta 1-1ceramide N-acetylgalactosaminyltransferase has been purified to apparent homogeneity from mouse liver. The purification procedure involved differential centrifugation for preparation of Golgi membranes, extraction of the enzyme with Triton X-100, and sequential chromatography on phosphocellulose, UDP-aldehyde adipic acid hydrazone agarose, UDP-hexanolamine-Sepharose, CM-Sepharose, and DEAE-Sepharose. At the phosphocellulose column chromatography step, the recovery of the enzyme activity was less than 25%, but it was enhanced up to 70% when the enzyme assay was performed in the presence of the flow-through fraction from the phosphocellulose column. With this assay, the enzyme activity was found to be quantitatively recovered during all the column chromatographies, the enzyme finally being purified 171,000-fold with a specific activity of 3.6 mumol/min/mg protein. The apparent molecular mass of the purified enzyme is 65,000 daltons. The enzyme exhibits a pH optimum of 7.5-7.9 and requires 2.5-10 mM Mn2+ for the maximal activity. The Km value for UDP-N-acetylgalactosamine is 7 microM. Among the glycolipids tested as acceptor substrates, NeuGc alpha 2-3Gal beta 1-4Glc beta 1-1ceramide, NeuAc alpha 2-3 Gal beta 1-4Glc beta 1-1ceramide, NeuGc alpha 2-8NeuGc alpha 2-3Gal beta 1-4Glc beta 1-1ceramide, and NeuAc alpha 2-8NeuAc alpha 2-3Gal beta 1-4Glc beta 1-1ceramide are good ones, the Km values for them being 160, 2,100, 27, and 350 microM, respectively, but sialyllactose, NeuAc alpha 2-3Gal beta 1-4Glc, is not. This suggests that the enzyme recognizes not only the oligosaccharide portion but also the ceramide of gangliosides.
authors.affiliation: Department of Membrane Biochemistry, Tokyo Metropolitan Institute of Medical Science, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Hashimoto
authors.forename: M
authors.initials: M
authors.lastname: Sekine
authors.forename: K
authors.initials: K
authors.lastname: Iwasaki
authors.forename: A
authors.initials: A
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D002240:Carbohydrate Sequence; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006056:Golgi Apparatus / Q000201:enzymology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D051379:Mice; D008811:Mice, Inbred DBA; D008969:Molecular Sequence Data; D017350:N-Acetylgalactosaminyltransferases / Q000302:isolation & purification* / Q000378:metabolism*; D017830:Octoxynol; D009844:Oligosaccharides / Q000378:metabolism; D013379:Substrate Specificity; D000097763:Polypeptide N-acetylgalactosaminyltransferase
chemical_list: D017350:N-Acetylgalactosaminyltransferases; D017830:Octoxynol; D009844:Oligosaccharides; D000097763:Polypeptide N-acetylgalactosaminyltransferase; C023220:(N-acetylneuraminyl)-galactosylglucosylceramide N-acetylgalactosaminyltransferase