Ganglioside biosynthesis in rat liver: characterization of cytidine-5'-monophospho-n-acetylneuraminic acid:hematoside (GM3) sialyltransferase.
CMP-NAcNeu:GM3 ganglioside sialytransferase (GD3 synthase) was concentrated 80-100-fold, relative to total homogenates, in Golgi apparatus fractions from rat liver. Ultrasound treatment of Golgi apparatus in a low salt medium extracted 40-60% of the original protein but did not dissociate the transferase from membranes. The acivity was greatest in the presence of certain detergents, had a pH optimum of 6.2, was stimulated by mg2+ and diacylphospholipids and was inhibited by lysophospholipids. Apparent Km values for CMP-NAcNeu and GM3 were about 0.8 and 0.2 mM, respectively. On chromatographic separation, virtually all the reaction product migrated as GD3. GD3 synthase appeared to be a glycoprotein since the activity bound to concanavalin A-Sepharose and was eluted, with increased specific activity, by alpha-methyl mannoside.
D000818:Animals; D002451:Cell Compartmentation; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid; D004721:Endoplasmic Reticulum / Q000201:enzymology; D005732:Gangliosides / Q000096:biosynthesis*; D006056:Golgi Apparatus / Q000201:enzymology / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D051381:Rats; D012799:Sialyltransferases / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism*
D005732:Gangliosides; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid; D014166:Transferases; D012799:Sialyltransferases