Subcellular Distribution of UDP‐Galactose:Ceramide Galactosyltransferase in Rat Brain Oligodendroglia

Abstract: Oligodendrocytes isolated from 18–19‐day‐old rat brain were homogenized in 0.32 M sucrose. The homogenate was centrifuged at 100,000 g for 50 min in a gradient containing 0.8, 1.05, and 1.3 M sucrose. Three discrete bands were obtained at the interfaces 0.32–0.8 (F1), 0.8–1.05 (F2), and 1.05–1.3 M (F3). The distribution of UDP‐galactose:ceramide galactosyltransferase (CgalT) activity in each fraction was measured using liposomes containing normal fatty acid‐containing ceramides (NFA‐CgalT activity) or 2‐hydroxy fatty acid‐containing ceramides (HFA‐CgalT activity). Although detection of both CgalT activities was possible in all fractions, HFA‐CgalT activity was enriched in F1 and F2 fractions, which also showed an enrichment of Golgi and endoplasmic reticulum markers, respectively. It is interesting that NFA‐CgalT activity was significantly enriched in the F2 fraction. These results suggest that hydroxylated and nonhydroxylated galactocerebrosides may be synthesized at different intracellular locations.