title: Leishmania beta-1,2-mannan is assembled on a mannose-cyclic phosphate primer.
abstract: Infective stages of the protozoan parasite Leishmania spp. accumulate a class of beta-1,2-mannan oligosaccharides as their major carbohydrate reserve material. Here, we describe the biosynthesis of Leishmania mannan. Mannan precursors were identified by metabolic labeling of Leishmania mexicana promastigotes with [(3)H]mannose. Label was initially incorporated into a phosphomannose primer and short phosphorylated beta-1,2-mannan oligomers that were two to five residues long. Analysis of the mannan primer by Fourier transform ion-cyclotron resonance MS and various enzymatic and chemical treatments and comparison with authentic mannose (Man) phosphates indicated the presence of Man-alpha-1,4-cyclic phosphate. This primer was synthesized from Man-6-phosphate by means of Man-1-phosphate in a cell-free system. Short mannan chains containing the primer were subsequently dephosphorylated and then further elongated by GDP-Man-dependent transferases in vivo and in the cell-free system. The synthesis of this glycan primer likely constitutes a key regulatory step in mannan biosynthesis and is a potential target for antileishmanial drugs.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia.
authors.forename: M Fleur
authors.initials: MF
authors.lastname: Sernee
authors.forename: Julie E
authors.initials: JE
authors.lastname: Ralton
authors.forename: Zoran
authors.initials: Z
authors.lastname: Dinev
authors.forename: George N
authors.initials: GN
authors.lastname: Khairallah
authors.forename: Richard A
authors.initials: RA
authors.lastname: O'Hair
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Williams
authors.forename: Malcolm J
authors.initials: MJ
authors.lastname: McConville
mesh_terms: D000818:Animals; D007891:Leishmania / Q000737:chemistry / Q000378:metabolism*; D008351:Mannans / Q000096:biosynthesis*; D008358:Mannose / Q000737:chemistry* / Q000378:metabolism*; D015394:Molecular Structure; D010710:Phosphates / Q000737:chemistry*
chemical_list: D008351:Mannans; D010710:Phosphates; C043364:beta-1,2-mannopyranan; D008358:Mannose