title: Direct sialic acid transfer from a protein donor to glycolipids of trypomastigote forms of Trypanosoma cruzi.
abstract: Labeled sialoglycolipids were purified from tissue culture-derived trypomastigotes incubated with [3H]fetuin. Thin layer chromatography of [3H]sialoglycolipids showed three components with the same migration as gangliosides extracted from parasites incubated with [3H]palmitic acid. Neuraminidase treatment or mild acid hydrolysis confirmed the presence of [3H]sialyl residues in sialoglycolipids synthesized after [3H]fetuin incubation. Labeling was not observed when parasites were incubated with free [3H]sialic acid (C7 derivative), suggesting that sialyl residues are directly transferred in vivo to gangliosides, by an enzymatic reaction possibly catalysed by a sialyl transferase (transglycosylase). Sonicated extracts of trypomastigotes incubated with [3H]fetuin catalysed the labeling of endogenous glycoconjugates as well as of bovine brain gangliosides. The transglycosylase activity was found associated with the particulate fraction and could be solubilized with Triton X-100. The specific activity of the sialic acid transglycosylase in epimastigotes is 17% of that found in trypomastigotes. Addition of an excess free sialic acid did not inhibit the reaction, suggesting that transfer does not occur via a pool of free sialic acid.
mesh_terms: D000818:Animals; D002854:Chromatography, Paper; D002855:Chromatography, Thin Layer; D006001:Glycoconjugates / Q000378:metabolism; D006017:Glycolipids / Q000378:metabolism*; D012794:Sialic Acids / Q000378:metabolism*; D012799:Sialyltransferases / Q000378:metabolism*; D014349:Trypanosoma cruzi / Q000201:enzymology / Q000378:metabolism*; D000509:alpha-Fetoproteins / Q000378:metabolism; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
chemical_list: D006001:Glycoconjugates; D006017:Glycolipids; D012794:Sialic Acids; D000509:alpha-Fetoproteins; C009255:sialoglycolipids; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase