Presence of an active GalactosylCeramide Synthase in Trypanosoma cruzi

J.E.PARENTE,; LANDONI M; V.DUSCHAK,; A.S.COUTO

Mar del Plata, Buenos Aires, Argentina.

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2007

Glycosphingolipids form a highly polymorphic class of lipids. In mammalian cells they occur in a number of cellular membranes but are mainly expressed on the cell surface, where they are thought to play a role in cell signaling and recognition. The carbohydrate structures in most glycolipid series are based on the (Galâ1-4Glcâ1) of lactosylceramide. Glucosylceramide therefore is the precursor for most glycolipid species. The other major monohexosylceramide, GalactosylCeramide, serves as a precursor for only a few simple glycolipids, sulfatide, galabiosylceramide, and the ganglioside sialo-Galceramide. Although the biochemical pathways of glycosphingolipid biosynthesis are relatively well understood in mammalian cells, little is known about them in parasites. Recently, we have shown the presence of an active glucosyl ceramide synthase in epimastigote forms of T.cruzi. In the present work, another enzyme of these pathways was detected for the first time and purified: a galatosyl ceramide synthase. CGalT activity was measured in lysates obtained from epimastigote forms of T.cruzi. Fractions, pretreated with saponine, were incubated at 37 °C in the presence of 2 mM UDP-Gal and NBD- ceramide. Lipids were extracted and separated by TLC. A putative CGalT was purified using a ConA-Sepharose column. On going studies are being carried out to determine the sequence of the purified protein.