Biosynthesis of lipophosphoglycan from Leishmania donovani: characterization of mannosylphosphate transfer in vitro.
Lipophosphoglycan (LPG) is the major surface glycoconjugate of Leishmania donovani promastigotes and is composed of a capped polymer of repeating PO4-6Gal(beta 1,4)Man alpha 1 disaccharide units linked via a phosphosaccharide core to a lyso-1-O-alkylphosphatidylinositol anchor. An exogenous acceptor composed of the glycolipid anchor portion of LPG was shown to stimulate the enzymatic synthesis of the repeating phosphorylated disaccharide units of LPG in a cell-free system. Using the exogenous acceptor, GDP-[3H]Man, [beta-32P]GDP-Man, and unlabeled UDP-Gal as substrates, membrane preparations from an LPG-defective mutant of L. donovani that lacks endogenous acceptors catalyzed the incorporation of the doubly labeled mannosylphosphate unit into a product that exhibited the chemical and chromatographic characteristics of LPG. Analysis of fragments generated by mild acid hydrolysis of the radiolabeled product indicated that [3H]mannose-1-[32P]PO4 had been transferred from the dual-labeled sugar nucleotide. These results are consistent with the proposal that the repeating units of the L. donovani LPG are synthesized by the alternating transfer of mannose 1-phosphate and galactose from their respective nucleotide donors.
Carver
M A
MA
Department of Biochemistry, University of Kentucky Medical Center, Lexington 40536.
Turco
S J
SJ
D000818:Animals; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D002853:Chromatography, Liquid; D005690:Galactose / Q000378:metabolism; D006028:Glycosphingolipids / Q000096:biosynthesis* / Q000172:deficiency; D006868:Hydrolysis; D007893:Leishmania donovani / Q000235:genetics / Q000378:metabolism*; D008360:Mannosephosphates / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation
D006028:Glycosphingolipids; D008360:Mannosephosphates; C008290:lipophosphonoglycan; D005690:Galactose