Substrate specificity of the dolichol phosphate mannose: Glucosaminyl phosphatidylinositol alpha 1-4-mannosyltransferase of the glycosylphosphatidylinositol biosynthetic pathway of African trypanosomes

Terry K Smith, S Cottaz, J S Brimacombe, M A J Ferguson

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66 Citations (Scopus)

Abstract

The biosynthesis of glycosylphosphatidylinositol (GPI) precursors in Trypanosoma brucei involves the D-mannosylation of D-GlcN alpha 1-6-D-myo-inositol-1-PO4-sn-1,2-diacylglycerol (GlcN-PI). An assay for the first mannosyltransferase of the pathway, Dol-P-Man:GlcN-PI alpha 1-4-mannosyltransferase, is described. Analysis of the acceptor specificity revealed (a) that the enzyme requires the myo-inositol residue of the GlcN-PI substrate have the D configuration; (b) that the enzyme requires the presence of the NH2 group of the D-GlcN residue; (c) that GlcNAc-PI is more efficiently presented to the enzyme than GlcN-PI, suggesting a degree of substrate channelling via the preceding GlcNAc-PI de-N-acetylase enzyme; (d) that the fatty acid and phosphoglycerol components of the phosphatidyl moiety are important for enhancing substrate presentation and substrate recognition, respectively; and (e) that D-GlcN alpha 1-6-D-myo-inositol is the minimum structure that can support detectable acceptor activity. Analysis of the donor specificity revealed that short chain (C-5 and C-15) analogues of dolichol phosphate can act as substrates for the trypanosomal dolichol-phosphomannose synthetase, whereas the corresponding mannopyranosides cannot act as donors for the Dol-P-Man:GlcN-PI alpha 1-4-mannosyltransferase.

Original languageEnglish
Pages (from-to)6476-6482
Number of pages7
JournalJournal of Biological Chemistry
Volume271
Issue number11
Publication statusPublished - 15 Mar 1996

Keywords

  • VARIANT SURFACE GLYCOPROTEIN
  • NOCTURNAL HEMOGLOBINURIA CELLS
  • ANCHOR BIOSYNTHESIS
  • MEMBRANE ANCHORS
  • GLYCOPHOSPHATIDYLINOSITOL ANCHORS
  • STRUCTURAL CHARACTERIZATION
  • TOXOPLASMA-GONDII
  • MAMMALIAN-CELLS
  • PRECURSORS
  • BRUCEI

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