Glycolipid glycosyltransferase activities during early development of Xenopus: Effect of retinoic acid

Retinoic acid (RA) plays an important role in differentiation stage in which it also influences glycoconjugate metabolism. Previous work in our laboratory has shown that treatment with RA modifies glycolipid synthesis and distribution in total Xenopus embryos during development. In this study we have investigated the activity of the following anabolic enzymes involved in glycolipid biosynthesis: sialyltransferase-1 (SAT-1), GM3(beta 1,4)-N-acetylgalactosaminyltransferase (GalNAcT-1) and LacCer(beta 1,3)N-acetylglucosaminyltransferase (GlcNAcT-1). These enzymes are located at the branching point of lactosylceramide (Lc(2)) metabolism. Enzyme activities were assayed after treatment with different doses of RA added exogenously to the medium during the first 7 days of Xenopus embryo development. Our results show that RA activates GlcNAcT-1, the enzyme that drives Lc(2) to the glycolipids of the lacto-series, and SAT-1 that inserts Lc(2) in the ganglio-series pathway. These data support our previous analysis of glycolipid pattern in Xenopus embryos after RA treatment (Rizzo et al., 1995; Cell Biol Int 19. 895-901) indicating a possible correlation between the distribution of glycolipids and the enzymes involved in their metabolism.