PHOSPHORYLATION OF THE OLIGOSACCHARIDE OF UTEROFERRIN BY UDP-GLCNAC-GLYCOPROTEIN N-ACETYLGLUCOSAMINE-1-PHOSPHOTRANSFERASES FROM RAT-LIVER, ACANTHAMOEBA-CASTELLANI, AND DICTYOSTELIUM-DISCOIDEUM REQUIRES ALPHA-1,2-LINKED MANNOSE RESIDUES

  • 15 May 1986
    • journal article
    • research article
    • Vol. 261  (14) , 6326-6331
Abstract
We have investigated the oligosaccharide requirements of the UDP-GlcNAc:glycoprotein N-acetylglucosamine-1-phosphotransferases from rat liver, Acanthamoeba castellani, and Dictyostelium discoideum. Uteroferrin, an acid hydrolase, was phosphorylated by the three N-acetylglucosaminylphosphotransferases, and the phosphorylated oligosaccharides were isolated and analyzed by ion suppression high performance liquid chromatography. In all three cases, the phosphorylated species contained 6 or more mannose residues. Phosphorylation of the Man5GlcNAc2 oligosaccharide could not be detected even though this was the major species of the native uteroferrin. The Man5GlcNAc2 oligosaccharides lack .alpha.1,2-linked mannose residues, whereas the larger oligosaccharides contain 1 or more mannose residues in this linkage. Treatment of intact uteroferrin with an .alpha.1,2-specific mannosidase-generated molecules whose oligosaccharides consisted almost entirely of species with 5 mannose residues. The N-acetylglucosaminylphosphotransferases could not longer phosphorylate such molecules. These data indicate that at least 1 .alpha.1,2-linked mannose residue must be present on uteroferrin''s oligosaccharide for phosphorylation to occur.