Two glycosphingolipid sialyltransferases are localized in different sub-Golgi compartments in rat liver.
A highly purified Golgi preparation from rat liver was fractionated on a sucrose density gradient and the activity of two sialyltransferases, CMP-NeuAc: Gal beta 1----4Glc-Cer (lactosylceramide) alpha-2----3sialyltransferase; Sat-1), and CMP-NeuAc:Gal beta 1----3GalNAc beta 1----4(NeuAc alpha 2----3) Gal beta 1----4Glc-Cer (GM1 ganglioside) alpha 2----3sialyltransferase; SAT-4), involved in the biosynthesis of gangliosides were assayed in the collected fractions. These two activities were recovered in different regions of the gradient; SAT-1 was found in a more dense region than SAT-4. This distribution coincided with that of two N-Asn linked oligosaccharide processing enzymes (UDP-GlcNAc:lysosomal enzyme precursor GlcNAc-1-phosphotransferase and UDP-Gal:ovalbumin galactosyltransferase), assumed as putative markers of cis- and trans-Golgi cisternae, respectively. These findings are consistent with the assembly of ganglioside oligosaccharide chains occurring in different sub-Golgi compartments.
Department of Medical Chemistry and Biochemistry, Medical School, University of Milan, Italy.
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Trinchera
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Ghidoni
D000818:Animals; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D006056:Golgi Apparatus / Q000201:enzymology* / Q000648:ultrastructure; D007700:Kinetics; D008099:Liver / Q000201:enzymology* / Q000648:ultrastructure; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012799:Sialyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D013379:Substrate Specificity
D012799:Sialyltransferases; C019916:CMP-N-acetylneuraminic acid-monosialoganglioside sialyltransferase; C021343:haematoside synthetase