Characterization of Crithidia fasciculata oligosaccharide-lipid and its elongation by bovine mammary microsomes

Characterization of dolichol monophosphate- and dolichol diphosphate-linked saccharides in trypanosomatid flagellates

Dolichol-P- and dolichol-P-P-linked saccharides were isolated from several trypanosomatid flagellates incubated with [U-14C]glucose. Formation of Glc-P-dolichol and Man-P-dolichol was observed in Herpetomonas muscarum and Leishmania adleri, whereas only the latter derivative was synthesized in Trypanosoma dionisii and Leptomonas samueli. The main and largest dolichol-P-P-linked oligosaccharide formed in Trypanosoma conorhini, T. dionisii, L. samueli, Herpetomonas samuelpessoai and H. muscarum appeared to be Man9GlcNAc2, whereas in Blastocrithidia culicis it was Man6GlcNAc2. In L. adleri there were two main oligosaccharides linked to dolichol-P-P, Man6GlcNAc2 and Man5GlcNAc2. The The structures of the oligosaccharides were identical with those of the intermediates in the formation of Glc3Man9GlcNAc2-P-P-dolichol in higher eucaryotes. It was concluded that similarly to Trypanosoma cruzi, Crithidia fasciculata and Leishmania mexicana, no glucosylated derivatives of dolichol-P-P were formed in the additional seven trypanosomatids studied here. The results obtained suggest that the defective step could be in some cases the formation of Glc-P-dolichol and in others, the transfer of glucose residues from the latter compound to dolichol-P-P-linked oligosaccharides.

Developmental regulation of glycosyltransferases involved in biosynthesis of asparagine-linked glycoproteins in mouse mammary gland

Three glycosyltransferases, namely N-acetylglucosaminyl-1-phosphotransferase, mannosyltransferase and glucosyltransferase, involved in the biosynthesis of asparagine-linked glycoproteins in the mouse mammary gland, were identified by characterization of the products formed by these enzymes. The tissue capacities of the glycosyltransferases, measured as pmol product formed g tissue-1 min-1, increase during developmental cycle of the gland until, at late lactational stage, they reach more than 34, 14 and 60 times, respectively, the basal level found in the tissue of virgin animals. Among the three enzymes at late lactational stage the specific activities of glucosyltransferase and N-acetylglucosaminyl-1-phosphotransferase increase 7-fold and 4-fold respectively, whereas mannosyltransferase shows a mere 1.4-fold increase during tissue development. All of the enzymes, both in terms of tissue capacity and specific activity, return to the basal levels of the virgin gland one month after the end of lactation. The activities of the three enzymes in the lactating gland decrease precipitously following treatment of mice with bromocriptine, a drug that interferes with the release of prolactin from the pituitary gland and thereby inhibits milk synthesis and secretion. These results indicate that the three glycosyltransferases are developmentally regulated during the growth and differentiation of the mouse mammary gland.