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Identification of methylphosphomannosyl residues as components of the high mannose oligosaccharides of Dictyostelium discoideum glycoproteins.

Identification of methylphosphomannosyl residues as components of the high mannose oligosaccharides of Dictyostelium discoideum glycoproteins.

Authors :
Gabel CA
Costello CE
Reinhold VN
Kurz L
Kornfeld S
Source :
The Journal of biological chemistry [J Biol Chem] 1984 Nov 25; Vol. 259 (22), pp. 13762-9.
Publication Year :
1984

Abstract

Lysosomal enzymes isolated from the slime mold Dictyostelium discoideum bind to the mannose 6-phosphate receptor which is present in many mammalian cells. While binding to the receptor suggests that the slime mold enzymes possess the same mannose 6-phosphate recognition marker as their mammalian counterparts, initial structural studies of the phosphorylated oligosaccharides have indicated that the phosphate is attached to high mannose-type units via an unusual phosphodiester linkage (Freeze, H.H., Yeh, R., Miller, A.L., and Kornfeld, S. (1983) J. Biol. Chem. 258, 14874-14879). To identify the components of the phosphodiester group we have isolated the phosphorylated high-mannose oligosaccharides from D. discoideum AX3 cells labeled with [2-3H]mannose or [6-3H]glucosamine and from the differentiation medium of unlabeled cells. The major phosphorylated species contain one or two phosphodiester groups and an average of 6 or 7 mannose residues. The phosphodiesters are relatively stable to both acid and base hydrolysis, but upon strong acid hydrolysis (conditions that completely hydrolyze the oligosaccharide) mannose 6-phosphate residues are liberated. Through a combination of techniques, including fast atom bombardment and direct chemical ionization mass spectrometry, it is shown that the mannose 6-phosphate residues of the intact oligosaccharide are diesterified to methyl groups. This indicates that slime mold possesses a different biosynthetic pathway for the formation of phosphorylated high mannose-type oligosaccharides than is utilized by higher organisms.

Details

Language :
English
ISSN :
0021-9258
Volume :
259
Issue :
22
Database :
MEDLINE
Journal :
The Journal of biological chemistry
Publication Type :
Academic Journal
Accession number :
6501278